GIFT   OF 


1 nee ring  Libra 


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'    »*•  "^  '  >  ,\ 


MANUAL 


OF 


ELEMENTARY  GEOLOGYr 


OB, 


THE  ANCIENT  CHANGES  OF  THE  EARTH  AND  ITS  INHABITANTS 
AS  ILLUSTRATED  BY  GEOLOGICAL  MONUMENTS. 


BY  SIR  CHARLES  LTELL,  M.A.  F.R.S. 

AUTHOR  OF  "PRINCIPLES  OF  GEOLOGY,"  ETC. 


"  It  is  a  philosophy  which  never  rests— its  law  is  progress  :  a  point  which  yesterday  was 
invisible  is  its  goal  to-day,  and  will  be  its  starting-post  to-morrow." 

EDIHBUBGH  RIVIEW,  July,  1837. 


HDMMOI.IT3.  A1C1COVITB.  TRH.OBIT* 


TERTIARY.  SECONDARY.  PRIMARY. 

KEPRINTED    FROM   THE   SIXTH   EDITION,    GREATLY   ENLARGED. 

SUustraUU  toftji  750  «®oottcuts. 


NEW  YORK: 
D.  APPLETON    AND    COMPANY, 

846  &   348   BEOADWAY. 

1858. 


A* 


ENGINEERING  LIBRARY 


PREFACE  TO  THE  FIFTH  EDITION. 


IT  is  now  more  than  three  years  since  the  appearance  of  the 
last  Edition  of  the  Manual  (published  January,  1851).  In  that 
interval  the  science  of  Geology  has  been  advancing  as  usual 
at  a  rapid  pace,  making  it  desirable  to  notice  many  new  facts 
and  opinions,  and  to  consider  their  bearing  on  the  previously 
acquired  stock  of  knowledge.  In  iny  attempt  to  bring  up  the 
information  contained  in  this  Treatise  to  the  present  state  of 
the  science,  I  have  added  no  less  than  200  new  Illustrations 
and  140  new  pages  of  Text,  which,  if  printed  separately  and  in 
a  less  condensed  form,  might  have  constituted  alone  a  volume 
of  respectable  size.  To  give  in  detail  a  list  of  all  the  minor 
corrections  and  changes  would  be  tedious ;  but  I  have  thought 
it  useful,  in  order  to  enable  the  reader  of  former  editions  to 
direct  his  attention  at  once  to  what  is  new,  to  offer  the  follow- 
ing summary  of  the  more  important  additions  and  alterations. 

Principal  Additions  and  Alterations  in  the  present  Edition. 

CHAP.  IX. — "The  general  Table  of  Fossiliferous  strata,"  formerly 
placed  at  the  end  of  Chapter  Xx'yi'f.,  is  now  given  at  p.  104,  that  the 
beginner  may  accustom  himself  from  the  first  to  refer  to  it  from  time  to 
time  when  studying  the  numerous  subdivisions  into  which  it  is  now 
necessary  to  separate  the  chronological  series  of  rocks.  The  Table  has 
been  enlarged  by  a  column  of  Foreign  Equivalents,  comprising  the  names 
and  localities  of  some  of  the  best  known  strata  in  other  countries  of  con- 
temporaneous date  with  British  Formations. 

CHAP.  XIV. — XVI. — The  classification  of  the  Tertiary  formations  has 
been  adapted  to  the  information  gained  by  me  during  a  tour  made  in  the 
summer  of  1851  in  France  and  Belgium.  The  results  of  my  survey  were 
printed  in  the  Quarterly  Journal  of  the  Geological  Society  of  London  for 


855672 


VI  PEEFACE  TO  THE  FIFTH  EDITION". 

1852.  In  the  course  of  my  investigations  I  enjoyed  opportunities  of 
determining  more  exactly  the  relations  of  the  Antwerp  and  the  Suffolk 
crag,  p.  173 ;  the  stratigraphical  place  of  the  Bolderberg  beds  near 
Hasselt,  p.  178 ;  that  of  the  Limburg  or  Kleyn  Spawen  strata,  p.  188  ; 
and  of  other  Belgian  and  French  deposits.  In  reference  to  some  of  these, 
the  questions  so  much  controverted  of  late,  whether  certain  groups  should 
be  called  Lower  Miocene  or  Upper  Eocene,  are  fully  discussed,  p.  183, 
et  seq. 

In  the  winter  of  1852, 1  had  the  advantage  of  examining  the  northern 
part  of  the  Isle  of  Wight,  in  company  with  my  friend  the  late  lamented 
Professor  Edward  Forbes,  who  pointed  out  to  me  the  discoveries  he  had 
just  made  in  regard  to  the  true  position  of  the  Hempstead  series 
(pp.  185-192),  recognized  by  him  as  the  equivalent  of  the  Kleyn 
Spawen  or  Limburg  beds,  and  his  new  views  in  regard  to  the  relation  of 
various  members  of  the  Eocene  series  between  the  Hempstead  and  Bag- 
shot  beds.  An  account  of  these  discoveries,  with  the  names  of  the  new 
subdivisions,  is  given  at  pp.  208  et  seq. ;  the  whole  having  been  revised 
when  in  print  by  Edward  Forbes. 

The  position  assigned  by  Mr.  Prestwich  to  the  Thanet  sands,  as  an 
Eocene  formation  inferior  to  the  Woolwich  beds,  is  treated  of  at  p.  221, 
and  the  relations  of  the  Middle  and  Lower  Eocene  of  France  to  various 
deposits  in  the  Isle  of  Wight  and  Hampshire  at  p.  222  et  seq.  In  the 
same  chapters,  many  figures  have  been  introduced  of  characteristic  or- 
ganic remains,  not  given  in  previous  editions. 

CHAP.  XVII. — In  speaking  of  the  Cretaceous  strata,  I  have  for  the  first 
time  alluded  to  the  position  of  the  Pisolitic  Limestone  in  France,  and 
other  formations  in  Belgium  intermediate  between  the  White  Chalk  and 
Thanet  beds,  p.  235. 

CHAP.  XVm. — The  Wealden  beds,  comprising  the  Weald  Clay  and 
Hastings  Sands  apart  from  the  Purbeck,  are  in  this  chapter  for  the  first 
time  considered  as  belonging  to  the  Lower  Cretaceous  Group,  and  the 
reasons  for  the  change  are  stated  at  p.  263. 

CHAP.  XIX.— Relates  to  "the  denudation  of  the  Weald,"  or  of  the 
country  intervening  between  the  North  and  South  Downs.  It  has  been 
almost  entirely  rewritten,  and  some  new  illustrations  introduced.  Many 
geologists  have  gone  over  that  region  again  and  again  of  late  years, 
bringing  to  light  new  facts,  and  speculating  on  the  probable  time,  extent, 
and  causes  of  so  vast  a  removal  of  rock.  I  have  endeavored  to  show  how 
numerous  have  been  the  periods  of  denudation,  how  vast  the  duration  of 
some  of  them,  and  how  little  the  necessity  to  despair  of  solving  the  prob- 
lem by  an  appeal  to  ordinary  causation,  or  to  invoke  the  aid  of  imagi- 
nary catastrophes  and  paroxysmal  violence,  pp.  271-290. 

CHAP.  XX.— XXI.— On  the  strata  from  the  Oolite  to  the  Lias  inclu- 
sive. The  Purbeck  beds  are  here  for  the  first  time  considered  as  the 
uppermost  member  of  the  Oolite,  in  accordance  with  the  opinions  of  the 


PREFACE   TO   THE   FIFTH   EDITION.  vii 

late  Professor  E.  Forbes,  p.  294.  Many  new  figures  of  fossils  character- 
istic of  the  subdivisions  of  the  three  Purbecks  are  introduced ;  and  the 
discovery,  in  1854,  of  a  new  mammifer  alluded  to,  p.  295. 

Representations  also  of  fossils  of  the  Upper,  Middle,  and  Lower  Oolite, 
and  of  the  Lias,  are  added  to  those  before  given. 

CHAP.  XXTT. — XX1L1. — On  the  Triassic  and  Permian  formations. 
The  improvements  consist  chiefly  of  new  illustrations  of  fossil  remains. 

CHAP.  XXfV. — XXY. — Treating  of  the  Carboniferous  group,  I  have 
mentioned  the  subdivisions  now  generally  adopted  for  the  classification  of 
the  Irish  strata  (p.  359),  and  I  have  added  new  figures  of  fossil  plants  to 
explain,  among  other  topics,  the  botanical  characters  of  Calamites,  Stern- 
bergia,  and  Trigonocarpum,  and  their  relation  to  Coniferae  (pp.  364,  365, 
368).  The  grade  also  of  the  Coniferse  in  the  vegetable  kingdom,  and 
whether  they  hold  a  high  or  a  low  position  among  flowering  plants,  is  dis- 
cussed with  reference  to  the  opinions  of  several  of  the  most  eminent 
living  botanists ;  and  the  bearing  of  these  views  on  the  theory  of  progres- 
sive development,  p.  3  TO. 

The  casts  of  rain-prints  in  coal-shale  are  represented  in  several  wood- 
cuts as  illustrative  of  the  nature  and  humidity  of  the  carboniferous 
atmosphere,  p.  381.  The  causes  also  of  the  purity  of  many  seams  of 
coal,  p.  382,  and  the  probable  length  of  time  which  was  required  to 
allow  the  solid  matter  of  certain  coal-fields  to  accumulate,  p.  383,  are 
discussed  for  the  first  time. 

Figures  are  given  of  Crustaceans  and  Insects  from  the  Coal,  pp. 
385,  386 ;  and  the  discovery  of  some  new  Reptiles  is  alluded  to,  p.  401. 

I  have  also  alluded  to  the  causes  of  the  rarity  of  vertebrate  and  inver- 
tebrate air-breathers  in  the  coal,  p.  401. 

That  division  of  this  same  chapter  (Chap.  XXV.)  which  relates  to  the 
Mountain  Limestone  has  been  also  enlarged  by  figures  of  new  fossils,  and 
among  others  by  representations  of  Corals  of  the  Paleozoic,  as  distin- 
guishable from  those  of  the  Neozoic,  type,  p.  403  ;  also  by  woodcuts  of 
several  genera  of  shells  which  retain  the  patterns  of  their  original  colors, 
p.  406.  The  foreign  equivalents  of  the  Mountain  Limestone  are  also 
alluded  to,  p.  409. 

CHAP.  XXVL — In  speaking  of  the  Old  Red  Sandstone,  or  Devonian 
Group,  the  evidence  of  the  occurrence  of  the  skeleton  of  a  Reptile  and 
the  footprints  of  a  Chelonian  in  that  series  are  reconsidered,  p.  412. 
New  plants  found  in  Ireland  in  this  formation  are  figured,  p.  414  ;  also 
the  Pterygotus,  or  large  crustacean  of  Forfarshire,  p.  415  ;  and,  lastly,  the 
division  of  the  Devonian  series  in  North  Devon  into  Upper,  Middle,  and 
Lower,  p.  420,  the  fossils  of  the  same  (p.  421  et  seq.),  and  the  equivalents 
of  the  Devonian  beds  in  Russia  and  the  United  States,  are  treated  of, 
p.  425  and  428. 

CHAP.  XXVII. — The  classification  and  nomenclature  of  the  Silurian 
rockg  of  Great  Britain,  the  Continent  of  Europe,  and  North  America,  and 
the  question  whether  they  can  be  distinguished  from  the  Cambrian,  and 


Vlll  PKEFACE  TO  THE  FIFTH  EDITION. 

by  what  paleontological  characters,  are  discussed  in  this  chapter,  pp.  429, 
447,  and  453. 

The  relation  of  the  Caradoc  Sandstone  to  the  Upper  and  Lower  Silu- 
rian, as  inferred  from  recent  investigations  (p.  437),  the  vast  thickness  of 
the  Llandeilo  or  Lower  Silurian  in  Wales  (p.  442),  the  Obolus  or  Ungu- 
lite  grit  of  St.  Petersburg  and  its  fossils  (p.  443),  the  Silurian  strata  of 
the  United  States  and  their  British  equivalents  (p.  444),  and  those  of 
Canada,  the  discoveries  of  M.  Barrande  respecting  the  metamorphosis  of 
Silurian  and  Cambrian  trilobites  (pp.  441,  450),  are  among  the  subjects 
enlarged  upon  more  fully  than  in  former  editions,  or  now  treated  of  for 
the  first  time. 

The  Cambrian  beds  below  the  Llandeilo,  and  their  fossils,  are  likewise 
described  as  they  exist  in  Wales,  Ireland,  Bohemia,  Sweden,  the  United 
States,  and  Canada,  and  some  of  their  peculiar  organic  remains  are  fig- 
ured, p.  447  to  p.  453. 

Lastly,  at  the  conclusion  of  the  chapter,  some  remarks  are  offered  re- 
specting the  absence  of  the  remains  of  fish  and  other  vertebrata  from  the 
deposits  below  the  Upper  Silurian,  p.  453,  in  elucidation  of  which  topic 
a  Table  has  been  drawn  up  of  the  dates  of  the  successive  discovery  of  dif- 
ferent classes  of  Fossil  Vertebrata  in  rocks  of  higher  and  higher  anti- 
quity, showing  the  gradual  progress  made  in  the  course  of  the  last 
centuiy  and  a  half  in  tracing  back  each  class  to  more  and  more  ancient 
rocks.  The  bearing  of  the  positive  and  negative  facts  thus  set  forth  on 
the  doctrine  of  progressive  development  is  then  discussed,  and  the 
grounds  of  the  supposed  scarcity  both  of  vertebrate  and  invertebrate  air- 
breathers  in  the  most  ancient  formation  considered,  p.  456. 

CHAP.  XXVni. — With  the  assistance  of  an  able  mineralogist,  M. 
Delesse,  I  have  revised  and  enlarged  the  glossary  of  the  more  abundant 
volcanic  rocks,  p.  472,  and  the  table  of  analyses  of  simple  minerals, 
p.  475. 

CHAP.  XXIX. — In  consequence  of  a  geological  excursion  to  Madeira 
and  the  Canary  Islands,  which  I  made  in  the  winter  of  1853-4, 1  have 
been  enabled  to  make  larger  additions  of  original  matter  to  this  chapter 
than  tc  any  other  in  the  work.  The  account  of  Tenerifie  and  Madeira, 
pp.  510,  518,  is  wholly  new.  Formerly  I  gave  an  abstract  of  Von  Buch's 
description  of  the  island  of  Palma,  one  of  the  Canaries,  but  I  have  now 
treated  of  it  more  fully  from  my  own  observations,  regarding  Palma  as  a 
good  type  of  that  class  of  volcanic  mountains  which  have  been  called  by 
Von  Buch  "  craters  of  elevation,"  pp.  494-508.  Many  illustrations, 
chiefly  from  the  pencil  of  my  companion  and  fellow-laborer,  Mr.  Hartung, 
have  been  introduced.  In  reference  to  the  above-mentioned  subjects, 
citations  are  made  from  Dana  on  the  Sandwich  Islands,  p.  489,  and  from 
Junghuhn's  Java,  p.  492. 

CHAP.  XXXV.— XXXVII.— The  theory  of  the  origin  of  the  meta- 
morphic  rocks  and  certain  views  recently  put  forward  by  some  geolo- 
gists respecting  cleavage  and  foliation  have  made  it  desirable  to  recast 


PKEFACE  TO  THE  FIFTH  EDITION.  ix 

and  rewrite  a  portion  of  these  chapters.  New  proofs  are  cited  in  favor  of 
attributing  cleavage  to  mechanical  force,  p.  603,  and  for  inferring  in  many 
cases  a  connection  between  foliation  and  cleavage,  p.  608.  At  the  same 
time,  the  question — how  far  the  planes  of  foliation  usually  agree  with 
those  of  sedimentary  deposition,  is  entered  into,  p.  607. 

CHAP.  XXXVIII. — To  the  account  formerly  published  of  mineral 
veins,  some  facts  and  opinions  are  added  respecting  the  age  of  the  rocks 
and  alluvial  deposits  containing  gold  in  South  America,  the  United 
States,  California,  and  Australia. 


I  have  already  alluded  to  the  assistance  afforded  me  by  the 
late  Professor  Edward  Forbes  towards  the  improvement  of 
some  parts  of  this  work.  His  letters  suggesting  corrections 
and  additions  were  continued  to  within  a  few  weeks  of  his 
sudden  and  unexpected  death,  and  I  felt  most  grateful  to  him 
for  the  warm,  interest,  which,  in  the  midst  of  so  many  and 
pressing  avocations,  he  took  in  the  success  of  my  labors.  His 
friendship,  and  the  power  of  referring  to  his  sound  judgment  in 
cases  of  difficulty  on  paleontological  and  other  questions,  were 
among  the  highest  privileges  I  have  ever  enjoyed  in  the  course 
of  my  scientific  pursuits.  Never  perhaps  has  it  been  the  lot  of 
any  Englishman,  who  had  not  attained  to  political  or  literary 
eminence,  more  especially  one  who  had  not  reached  his  fortieth 
year,  to  engage  the  sympathies  of  so  wide  a  circle  of  admirers, 
and  to  be  so  generally  mourned.  The  untimely  death  of  such 
a  teacher  was  justly  felt  to  be  a  national  loss  ;  for  there  was  a 
deep  conviction  in  the  minds  of  all  who  knew  him,  that  genius 
of  so  high  an  order,  combined  with  vast  acquirements,  true 
independence  of  character,  and  so  many  social  and  moral  ex- 
cellences, would  have  inspired  a  large  portion  of  the  rising 
generation  with  kindred  enthusiasm  for  branches  of  knowledge 
nitherto  neglected  in  the  education  of  British  youth. 

As  on  former  occasions,  I  shall  take  this  opportunity  of 
stating  that  the  "  Manual"  is  not  an  epitome  of  the  "  Principles 
of  Geology,"  nor  intended  as  introductory  to  that  work.  So 
much  confusion  has  arisen  on  this  subject,  that  it  is  desirable 
to  explain  fully  the  different  ground  occupied  by  the  two  pub- 
lications. The  first  five  editions  of  the  "  Principles"  comprised 
a  4th  book,  in  which  some  account  was  given  of  systematic 


X  PEEFACE  TO  THE  FIFTH  EDITION. 

geology,  and  in  which  the  principal  rocks  composing  the 
earth's  crust  and  their  organic  remains  were  described.  In 
subsequent  editions  this  4th  book  was  omitted,  it  having  been 
expanded,  1838,  into  a  separate  treatise  called  the  "  Elements 
of  Geology,"  first  re-edited  in  1842,  and  again  recast  and  en- 
larged in  1851,  and  entitled  "  A  Manual  of  Elementary  Geol- 
ogy." Of  this  enlarged  work  another  edition,  called  the 
Fourth,  was  published  in  1852. 

Although  the  subjects  of  both  treatises  relate  to  Geology,  as 
their  titles  imply,  their  scope  is  very  different ;  the  "  Princi- 
ples" containing  a  view  of  the  modern  changes  of  the  earth  and 
its  inhabitants,  while  the  "  Manual"  relates  to  the  monuments 
of  ancient  changes.  In  separating  the  ene  from  the  other,  I 
have  endeavored  to  render  each  complete  in  itself,  and  inde- 
pendent ;  but  if  asked  by  a  student  which  he  should  read  first, 
I.  would  recommend  him  to  begin  with  the  "  Principles,"  as 
he  may  then  proceed  from  the  known  to  the  unknown,  and  be 
provided  beforehand  with  a  key  for  interpreting  the  ancient 
phenomena,  whether  of  the  organic  or  inorganic  world,  by 
reference  to  changes  now  in  progress. 

It  will  be  seen  on  comparing  "  The  Contents"  of  the  "  Prin- 
ciples" with  the  abridged  headings  of  the  chapters  of  the 
present  work  (see  the  following  pages),  that  the  two  treatises 
have  but  little  in  common ;  or,  to  repeat  what  I  have  said  in 
the  Preface  to  the  "  Principles,"  they  have  the  same  kind  of 
connection  which  Chemistry  bears  to  Natural  Philosophy,  each 
being  subsidiary  to  the  other,  and  yet  admitting  of  being  con- 
sidered as  different  departments  of  science.* 

CHAELES  LYELL. 

53  Barley-street,  London,  February  22,  1855. 

*  As  it  is  impossible  to  enable  the  reader  to  recognize  rocks  and  minerals  at 
sight  by  aid  of  verbal  descriptions  or  figures,  he  will  do  well  to  obtain  a  well- 
arranged  collection  of  specimens,  such  as  may  be  procured  from  Mr.  Tennant  (149 
Strand),  teacher  of  Mineralogy  at  King's  College,  London. 


CONTENTS. 


CHAPTER  L—  On  the  different  Classes  of  Rock*. 

Geology  defined — Successive  formation  of  the  earth's  crust — Classification  of 
rocks  according  to  their  origin  and  age — Aqueous  rocks — Volcanic  rocks — 
Plutonic  rocks — Metamorphic  rocks — The  term  primitive,  why  erroneously 
applied  to  the  crystalline  formations  <  -  -  I*age  1 

CHAPTER  II. — Aqueous  Rocks — Their  Composition  and  Forms  of  Stratification. 

Mineral  composition  of  strata — Arenaceous  rocks — Argillaceous — Calcareous — 
Gypsum — Forms  of  stratification — Diagonal  arrangement — Ripple-mark  10 

CHAPTEE  IH — Arrangement  of  Fossils  in  Strata — Freshwater  and  Marine. 

Limestones  formed  of  corals  and  shells — Proofs  of  gradual  increase  of  strata  de- 
rived from  fossils — Tripoli  and  semi-opal  formed  of  infusoria — Chalk  derived 
principally  from  organic  bodies — Distinction  of  freshwater  from  marine  forma- 
tions— Alternation  of  marine  and  freshwater  deposits  -  -  21 

CHAPTEE  IV. — Consolidation  of  Strata  and  Petrifaction  of  Fossils. 

Chemical  and  mechanical  deposits — Cementing  together  of  particles — Concre- 
tionary nodules — Consolidating  effects  of  pressure — Mineralization  of  organic 
remains — Impressions  and  casts  how  formed — Fossil  wood — Source  of  lime  and 
silex  in  solution  -  -  -  -  -  -  -  -33 

CHAPTER  V. — Elevation  of  Strata  above  the  Sea — Horizontal  and  Inclined 
Stratification. 

Position  of  marine  strata,  why  referred  to  the  rising  up  of  the  land,  not  to  the 
going  down  of  the  sea — Upheaval  of  horizontal  strata — Inclined  and  vertical 
stratification — Anticlinal  and  synclinal  lines — Theory  of  folding  by  lateral 
movement — Creeps — Dip  and  strike — Structure  of  the  Jura — Inverted  posi- 
tion of  disturbed  strata — Unconfonnable  stratification — Fractures  of  strata — 
Faults  ....  ....  44 

CHAPTER  VL — Denudation. 

Denudation  defined — Its  amount  equal  to  the  entire  mass  of  stratified  deposits  in 
the  earth's  crust — Levelled  surface  of  countries  in  which  great  faults  occur — 
Denuding  power  of  the  ocean — Origin  of  Valleys — Obliteration  of  sea-cliffs — 
Inland  sea-cliffs  and  terraces  ....  -  66 

CHAPTER  VLL — Alluvium. 

Alluvium  described — Due  to  complicated  causes — Of  various  ages — How  distin- 
guished from  rocks  in  situ — River- terraces — Parallel  roads  of  Glen  Roy  79 

CHAPTER  VHL — Chronological  Classification  of  Rocks. 

Aqueous,  plutonic,  volcanic,  and  metamorphic  rocks,  considered  chronologically 
— Lehman's  division  into  primitive  and  secondary — Werner's  addition  of  a 
transition  class — Neptunian  theory — Hutton  on  igneous  origin  of  granite — 
The  name  of  "  primary"  for  granite  and  the  term  "  transition"  why  faulty — 
Chronological  nomenclature  adopted  in  this  work,  so  far  as  regards  primary, 
secondary,  and  tertiary  periods  ....  89 


xii  CONTENTS. 


CHAPTER  IX. — On  the  different  Ages  of  the  Aqueous  Rocks. 

On  the  three  tests  of  relative  age— superposition,  mineral  character,  and  fossils- 
Change  of  mineral  character  and  fossils  in  the  same  formation — Proofs  that 
distinct  species  of  animals  and  plants  have  lived  at  successive  periods — Dis- 
tinct provinces  of  indigenous  species — Similar  laws  prevailed  at  successive 
geological  periods — Test  of  age  by  included  fragments — Frequent  absence  of 
strata  of  intervening  periods — General  Table  of  Fossiliferous  strata  Page  96 

CHAPTER  X. — Classification  of  Tertiary  Formations. — Post  Pliocene  Group. 

General  principles  of  classification  of  tertiary  strata — Difficulties  in  determining 
their  chronology — Increasing  proportion  of  living  species  of  shells  in  strata 
of  newer  origin — Terms  Eocene,  Miocene,  and  Pliocene — Post-Pliocene  recent 
strata  -  L  - '  -  -  109 

CHAPTER  XI. — Newer  Pliocene  Period. — Boulder  Formation. 

Drift  of  Scandinavia,  northern  Germany,  and  Russia — Fundamental  rocks  pol- 
ished, grooved,  and  scratched — Action  of  glaciers  and  icebergs — Fossil  shells 
of  glacial  period — Drift  of  eastern  Norfolk — Ancient  glaciers  of  North  Wales 
—Irish  drift  -  -  126 

CHAPTER  XII. — Boulder  Formation — continued. 

Effects  of  intense  cold  in  augmenting  the  quantity  of  alluvium — Analogy  of  er- 
ratics and  scored  rocks  in  North  America,  Europe,  and  Canada — Why  organic 
remains  so  rare  in  northern  drift— Many  shells  and  some  quadrupeds  survived 
the  glacial  cold — Alps  an  independent  centre  of  dispersion  of  erratics — Me- 
teorite in  Asiatic  drift  -  -  <  •"•'  -  -  -  137 

CHAPTER  XIII. — Newer  Pliocene  Strata  and  Cavern  Deposits. 

Pleistocene  formations — Freshwater  deposits  in  valley  of  Thames — In  Norfolk 
cliffs — In  Patagonia — Comparative  longevity  of  species  in  the  mammalia  and 
testacea — Crag  of  Norwich — Newer  Pliocene  strata  of  Sicily— Osseous  breccias 
and  cavern-deposits — Sicily — Kirkdale — Australian  cave-breccias — Relation- 
ship of  geographical  provinces  of  living  vertebrata  and  those  of  Pliocene  species 
— Teeth  of  fossil  quadrupeds  -  -  -  -  -152 

CHAPTER  XIV. — Older  Pliocene  and  Miocene  Formations. 

Red  and  Coralline  crags  of  Suffolk — Fossils,  and  proportion  of  recent  species — 
Depth  of  sea,  and  climate — Migration  of  many  species  of  shells  southwards 
during  the  glacial  period — Antwerp  crag — Subapennine  beds — Miocene  forma- 
ifans — Faluns  of  Touraine — Depth  of  sea  and  littoral  character  of  fauna — 
Climate — Proportion  of  recent  species  of  shells — Miocene  strata  of  Bordeaux, 
Belgium,  and  North  Germany — Older  Pliocene  and  Miocene  formations  in  the 
United  States— Sewalik  Hills  in  India  .r%:  -  -  -  -  167 

CHAPTER  XV. —  Upper  Eocene  Formations.     (Lower  Miocene  of  many  authors.) 

Remarks  on  classification,  and  on  the  line  of  separation  between  Eocene  and 
Miocene — Whether  the  Limburg  strata  in  Belgium  should  be  called  Upper 
Eocene — Strata  of  same  age  in  North  Germany — Mayence  basin — Brown  Coal 
of  Germany — Upper  Eocene  of  Isle  of  Wight — Of  France — Lacustrine  strata  of 
Auvcrgne  and  the  Cantal — Upper  Eocene  of  Bordeaux,  <fec. — Of  Nebraska, 
United  States  ........  188 

CHAPTER  XVI. — Middle  and  Lower  Eocene  Formations. 

Middle  Eocene  strata  of  England — Fluvio-marine  series  in  the  Isle  of  Wight  and 
Hampshire — Successive  groups  of  Eocene  Mammalia — Fossils  of  Barton  Clay 
— Of  the  Bagshot  and  Bracklesham  beds— Lower  Eocene  strata  of  England — 
London  Clay  proper — Strata  of  Kyson  in  Suffolk — Fossil  monkey  and  opossum 
—  Plastic  clays  and  sands — Thanet  sands  —  Middle  and  Lower  Eocene  for- 
mations of  France  —  Nummulitic  formations  of  Europe  and  Asia — Eocene 
strata  at  Claiborne,  Alabama — Colossal  cetacean — Orbitoid  limestone — Burr 
atone  -  -  -*'  •  *•  .....  207 


CONTENTS.  xiii 


CHAPTER  XVIL — Cretaceous  Group. 

Lapse  of  time  between  the  Cretaceous  and  Eocene  periods — Formations  in  Bel- 
gium and  France  of  intermediate  age — Pisolitic  limestone — Divisions  of  the 
Cretaceous  series  in  Northwestern  Europe — Maestricht  beds — Chalk  of  Faxoe 
—White  chalk — How  far  derived  from  shells  and  corals — Chalk  flints — Fossils 
of  the  Upper  Cretaceous  rocks — Upper  Greensand  and  Gault — Chalk  of  South 
of  Europe — Hippurite  limestone — Cretaceous  rocks  of  the  United  States  234 

CHAPTEE  XVHL — Lower  Cretaceous  and  Wealden  Formations. 

Lower  Greensand — Term  "  Neocomian" — Fossils  of  Lower  Greensand — Wealden 
formation — Weald  Clay  and  Hastings  Sand — Fossil  shells  and  fish — Their  re- 
lation to  the  Cretaceous  type  —  Flora  of  Lower  Cretaceous  and  Wealdea 
periods  ...--.---  256 

CHAPTER  XIX.— Denudation  of  the  Chalk  and  Wealden. 

Physical  geography  of  certain  districts  tcomposed  of  Cretaceous  and  Wealden 
strata — Lines  of  inland  chalk-cliffs  on  the  Seine  in  Normandy — Denudation  of 
the  chalk  and  wealden  in  Surrey,  Kent,  and  Sussex — Chalk  once  continuous 
from  the  North  to  the  South  Downs — Kise  and  denudation  of  the  strata  gradual 
— At  what  period  the  Weald  valley  was  denuded,  and  by  what  causes — Ele- 
phant-bed, Brighton— Sangatte  cliff—  Conclusion  -  -  -  267 

CHAPTER  XX. — Jurassic  Group. — Purbeck  Beds  and  Oolite. 

The  Purbeck  beds  a  member  of  the  Upper  Oolite — New  fossil  mammifer — Dirt- 
bed — Fossils  of  the  Purbeck  beds — Portland  stone  and  fossils — Middle  Oolite 
— Coral  Rag — Zoophytes — Nerinaean  limestone — Diceras  limestone  —  Oxford 
Clay,  Ammonites  and  Belemnites — Lower  Oolite,  Crinoideans — Great  Oolite 
— Stonesfield  Slate — Fossil  mammalia — Yorkshire  Oolitic  coal-field — Brora 
coal— Fuller's  Earth— Inferior  Oolite  and  fossils  -  *  *  -  291 

CHAPTER  XXL — Jurassic  Group,  continued. — Lias, 

Mineral  character  of  Lias — Fossil  shells  and  fish— Radiata — Ichthyodorolites — 
Reptiles — Ichthyosaur  and  Plesiosaur — Fluvio-marine  beds  in  Gloucestershire, 
and  Insect  limestone — Fossil  plants — Origin  of  the  Oolite  and  lias— Oolitic 
coal-field  of  Virginia  -  ....  317 

CHAPTER  XXII.— Trias  or  New  Red  Sandstone  Group. 

Distinction  between  New  and  Old  Red  Sandstone — The  Trias  and  its  three  di 
visions  in  Germany — Keuper  and  its  fossils — Muschelkalk  and  fossils — Fossil 
plants  of  the  Bunter — Triassic  group  in  England — Footsteps  of  Cheirotherium 
— Osteology  of  the  Ldbyrinlhodon — Triassic  mammifer — Origin  of  Red  Sand- 
stone and  Rock-salt — New  Red  Sandstone  in  the  United  States — Fossil  foot- 
prints of  birds  and  reptiles  in  the  valley  of  the  Connecticut  -  -  332 

CHAPTER  XXUL — Permian  or  Magnesian  Limestone  Group. 

Fossils  of  Magnesian  Limestone — Term  Permian — English  and  German  equiva- 
lents— Marine  shells  and  corals — Palaeoniscus  and  other  fish — Thecodont  sau- 
rians — Permian  Flora — Its  generic  affinity  to  the  carboniferous — Psaronites  or 
tree-ferns  ----  ....  350 

CHAPTER  XXIV. — The  Coal,  or  Carboniferous  Group. 

Carboniferous  strata  in  England — Coal-measures  and  mountain  limestone — Car- 
boniferous series  in  Ireland  and  South  Wales — Underclays  with  Stigmaria — 
Carboniferous  Flora — Ferns,  Lepidodendra,  Calamites,  Sigillariae — Coniferae — 
Sternbergia — Trigonocarpon — Grade  of  Coniferae  in  the  Vegetable  Kingdom — 
Absence  of  Angiosperms — Coal,  how  formed — Erect  fossil  trees — Rain-prints 
—Purity  of  the  Coal  explained— Time  required  for  its  accumulation— Crusta- 
ceans and  insects  -  -  -  -  -  -  ••  358 


CONTENTS. 


CHAPTER  XXV. — Carboniferous  Group — continued. 

Coal-fields  of  the  United  States — Section  of  the  country  between  the  Atlantic 
and  Mississippi — Uniting  of  many  coal-seams  into  one  thick  bed — Vast  extent 
and  continuity  of  single  seams  of  coal — Ancient  river-channel  in  Forest  of  Dean 
coal-field — Climate  of  Carboniferous  period — Insects  in  coal — Great  number  of 
fossil  fish — First  discovery  of  the  skeletons  of  fossil  reptiles — First  land-shell  of 
the  coal  found — Rarity  of  air-breathers,  whether  vertebrate  or  invertebrate,  in 
Coal-measures — Mountain  limestone — Its  corals  and  marine  shells  Page  387 


CHAPTER  XXVI. — Old  Red  Sandstone  or  Devonian  Group. 

Old  Red  Sandstone  of  the  borders  of  "Wales — Scotland  and  the  South  of  Ireland 
— Fossil  reptile  of  Elgin — Fossil  Devonian  plants  at  Kilkenny — Ichthyolites  of 
Clashbinnie — Fossil  fish,  <fcc.,  crustaceans,  of  Caithness  and  Forfarshire — Dis- 
tinct lithological  type  of  Old  Red  in  Devon  and  Cornwall — Term  "  Devonian" 
— Devonian  series  of  England  and  the  Continent — Old  Red  Sandstone  of  Russia 
— Devonian  strata  of  the  United  States  -  -  -  -  -  411 


CHAPTER  XXVII. — Silurian  and  Cambrian  Groups. 

Silurian  strata  formerly  called  "Transition" — Subdivisions — Ludlow  formation 
and  fossils — Ludlow  bone-bed,  and  oldest  known  remains  of  fossil  fish — Wen- 
lock  formation,  corals,  cystideans,  trilobites — Caradoc  sandstone — Pentameri 
and  Tentaculites— Lower  Silurian  rocks — Llandeilo  flags — Cystidese — Trilo- 
bites— Graptolites — Vast  thickness  of  Lower  Silurian  strata  in  Wales — Foreign 
Silurian  equivalents  in  Europe — Ungulite  grit  of  Russia — Silurian  strata  01 
the  United  States — Canadian  equivalents — Deep-sea  origin  of  Silurian  strata 
— Fossiliferous  rocks  below  the  Llandeilo  beds — Cambrian  group — Lingula 
flags — Lower  Cambrian — Oldest  known  fossil  remains — "  Primordial  group"  of 
Bohemia — Metamorphosis  of  trilobites — Alum  schists  of  Sweden  and  Norway 
— Potsdam  sandstone  of  United  States  and  Canada — Trilobites  on  the  Upper 
Mississippi  —  Supposed  period  of  invertebrate  animals  —  Absence  of  fish  in 
Lower  Silurian — Progressive  discovery  of  vertebrata  in  older  rocks — Doctrine 
of  the  non-existence  of  vertebrata  in  the  older  fossiliferous  periods  prema 
ture  -  -  -  429 

CHAPTER  XXVIIL—  Volcanic  Rocks. 

Trap  rocks — Name,  whence  derived — Their  igneous  origin  at  first  doubted — 
Their  general  appearance  and  character — Mineral  composition  and  texture — 
Varieties  of  felspar — Hornblende  and  augite — Isomorphism — Rocks,  how  to  be 
studied — Basalt,  trachyte,  greenstone,  porphyry,  scoria,  amygdaloid,  lava,  tuff 
— Agglomerate — Laterite — Alphabetical  list,  and  explanation  of  names  and 
synonyms  of  volcanic  rocks — Table  of  analyses  of  minerals  most  abundant  in 
the  volcanic  and  hypogene  rocks  -  -  *  i~  '  -  ,  -  460 

CHAPTER  XXIX. —  Volcanic  Rocks — continued. 

Trap  dikes — Strata  altered  at  or  near  the  contact — Conversion  of  chalk  into 
marble — Trap  interposed  between  strata — Columnar  and  globular  structure — 
Relation  of  trappean  rocks  to  the  products  of  active  volcanoes — Form,  exter- 
nal structure,  and  origin  of  volcanic  mountains — Craters  and  Calderas— Sand 
wich  Islands  —  Lava  flowing  underground  —  Truncation  of  cones — Javanese 
Calderas — Canary  Islands — Structure  and  origin  of  the  caldera  of  Palma — 
Aqueous  conglomerate  in  Palma — Hypothesis  of  upheaval  considered — Slope 
on  which  stony  lavas  may  form— Island  of  St.  Paul  in  the  Indian  Ocean — Peak 
of  Teneriffe,  and  ruins  of  older  cone — Madeira — Its  volcanic  rocks,  partly  of 
marine  and  partly  of  subaerial  origin — Central  axis  of  eruptions — Varying  dip 
of  solid  lavas  near  the  axis,  and  further  from  it — Leaf-bed  and  fossil  land- 
plants — Central  valleys  of  Madeira  how  formed  -  -  -  -  476 


CONTENTS.  XV 


CHAPTER  XXX. — On  the  Different  Ages  of  the  Volcanic  Rocks. 

Tests  of  relative  age  of  volcanic  rocks— Test  by  superposition  and  intrusion — 
Test  by  alteration  of  rocks  in  contact — Test  by  organic  remains — Test  of  age 
by  mineral  character — Test  by  included  fragments — Volcanic  rocks  of  the  Post- 
Pliocene  period — Basalt  of  Bay  of  Trezza  in  Sicily — Post-Pliocene  volcanic 
rocks  near  Naples — Dikes  of  Soinma — Igneous  formations  of  the  Newer  Plio- 
cene period— Val  di  Noto  in  Sicily  -  Page  519 

CHAPTER  "X"X"XT. — On  the  Different  Ages  of  the  Volcanic  Rocks— continued. 

Volcanic  rocks  of  the  Older  Pliocene  period — Tuscany — Rome— Volcanic  region 
of  Olot  in  Catalonia — Cones  and  lava-currents — Miocene  period — Brown-coal 
of  the  Eifel  and  contemporaneous  trachytic  rocks — Age  of  the  brown-coal — 
Peculiar  characters  of  the  volcanoes  of  the  Upper  and  Lower  Eifel — Lake  craters 
— Trass — Hungarian  volcanoes  -  -  -  630 

CHAPTER  XXXII. — On  the  Different  Ages  of  the  Volcanic  Rocks— continued. 

Volcanic  rocks  of  the  Pliocene  and  Miocene  periods  continued — Auvergne — Mont 
Dor — Breccias  and  alluviums  of  Mont  Perrier,  with  bones  of  quadrupeds — 
Mont  Dome — Cones  not  denuded  by  general  flood — Velay — Bones  of  quadru- 
peds buried  in  scoriae — Cantal — Eocene  volcanic  rocks — Tuffs  near  Clermont — 
Hill  of  Gergovia— Trap  of  Cretaceous  period — Oolitic  period — New  Red  Sand- 
stone period — Carboniferous  period — Old  Red  Sandstone  period — Silurian  pe- 
riod— Cambrian  volcanic  rocks  ...-.-  545 

CHAPTER  XXXIIL— Plutonic  Rocks— Granite. 

General  aspect  of  granite — Analogy  and  difference  of  volcanic  and  plutonic  for- 
mations— Minerals  in  granite — Mutual  penetration  of  crystals  of  quartz  and 
felspar — Syenitic,  talcose,  and  schorly  granites — Eurite — Passage  of  granite 
into  trap— Granite  veins  in  Glen  Tilt,  and  other  countries — Composition  of 
granite  veins — Metalliferous  veins  in  strata  near  their  junction  with  granite — 
Quartz  veins — Whether  plutonic  rocks  are  ever  overlying— Their  exposure 
at  the  surface  due  to  denudation  -  -  560 

CHAPTER  XXXIV.— On  the  different  Ages  of  the  Plutonic  Rocks. 

Difficulty  in  ascertaining  the  age  of  a  plutonic  rock — Test  of  age  by  relative  posi- 
tion— Test  by  intrusion  and  alteration — Test  by  mineral  composition — Test  by 
included  fragments — Recent  and  Pliocene  plutonic  rocks,  why  invisible — Ter- 
tiary plutonic  rocks  in  the  Andes — Granite  altering  Cretaceous  rocks — Granite 
altering  Lias — Granite  altering  Carboniferous  strata — Granite  of  the  Old  Red 
Sandstone  period — Syenite  altering  Silurian  strata  in  Norway — Oldest  plutonic 
rocks — Granite  protruded  in  a  solid  form — Age  of  the  granites  of  Arran,  in 
Scotland  -  ...  .  -  573 

CHAPTER  XXXV.— Metamorphic  Rocks. 

General  character  of  metamorphic  rocks — Gneiss — Hornblende-schist — Mica- 
schist — Clay-slate — Quartzite — Chlorite-schist — Metamorphic  limestone — Al- 
phabetical list  and  explanation  of  the  more  abundant  rocks  of  this  family — 
Origin  of  the  metamorphic  strata — Their  stratification — Fossiliferous  strata 
near  intrusive  masses  of  granite  converted  into  different  members  of  the  meta- 
morphic series — Objections  to  the  metamorphic  theory  considered — Partial 
conversion  of  Eocene  slate  into  gneiss  -  -  587 

CHAPTER  XXXVL — Metamorphic  Rocks — continued. 

Origin  of  the  metamorphic  rocks,  continued— Definition  of  joints,  slaty  cleavage, 
and  foliation — Causes  of  these  structures — Mechanical  theory  of  cleavage — 
Supposed  combination  of  crystalline  and  mechanical  forces — Lamination  of 
some  volcanic  rocks  due  to  motion — Whether  the  foliation  of  the  crystalline 
schists  be  usually  parallel  with  the  original  planes  of  stratification  -  600 


XVI  CONTENTS. 


CHAPTER  XXXVIL—  On  the  different  Ages  of  the  Metamorphic  Rocks. 

Age  of  each  set  of  metamorphic  strata  twofold— Test  of  age  by  fossils  and  min- 
eral character  not  available — Test  by  superposition  ambiguous — Conversion  of 
fossiliferous  strata  into  metamorphic  rocks — Limestone  and  shale  of  Carrara — 
Metamorphic  strata  older  than  the  Cambrian  rocks — Others  of  Lower  Silurian 
origin — Others  of  the  Jurassic  and  Eocene  periods — Why  scarcely  any  of  the 
visible  crystalline  strata  are  very  modern — Order  of  succession  in  metamorphic 
rocks — Uniformity  of  mineral  character — Why  the  metamorphic  strata  are 
less  calcareous  than  the  fossiliferous  •  -  -  Page  611 

CHAPTER  XXXVIII.— Mineral  Veins. 

Werner's  doctrine,  that  mineral  veins  were  fissures  filled  from  above — Veins  of 
segregation — Ordinary  metalliferous  veins  or  lodes — Their  frequent  coincidence 
with  faults — Proofs  that  they  originated  in  fissures  in  solid  rock — Veins  shifting 
other  veins — Polishing  of  their  walls  or  "  slicken-sides" — Shells  and  pebbles  in 
lodes — Evidence  of  the  successive  enlargement  and  reopening  of  veins — Why 
some  veins  alternately  swell  out  and  contract — Filling  of  lodes  by  sublimation 
from  below — Chemical  and  electrical  action — Relative  age  of  the  precious 
metals — Copper  and  lead  veins  in  Ireland  older  than  Cornish  tin — Lead  veins 
in  Lias,  Glamorganshire — Gold  in  Russia,  California,  and  Australia — Connec- 
tion of  hot  springs  and  mineral  veins — Concluding  remarks  :..'»  ^  .  618 


SUPPLEMENT. 

British  Pliocene  Strata — Proofs  from  fossil  shells  of  a  gradual  refrigeration  of  climate 
in  England,  at  the  successive  periods  of  the  Coralline,  the  Red,  and  the  Norwich 
Crag — Searles  Wood's  Monograph  on  the  Crag  Mollusca — The  Crag  Mastodon,  a 
Pliocene  species — Different  assemblages  of  fossil  Mammalia  in  the  freshwater  and 
drift  deposits  of  the  valley  of  the  Thames— Fossil  Musk-buffalo  in  the  drift  near 
London  and  near  Berlin  -  ...  page  635 

Where  to  draw  the  line  "between  the  Miocene  and  Eocene  Tertiary  Strata. 

Classification  of  the  Miocene  and  Eocene  strata— Where  to  draw  the  line  between 
Upper  Eocene  and  Lower  Miocene — Reasons  for  a  proposed  change  of  nomen- 
clature— Miocene  fossil  shells  and  quadrupeds  of  the  Sewalik  or  Sub-Hiinalayan 
Hills  -  -  -  -  -  -  -  -  -  -  640 

Miocene  Fauna  of  the  Sewalik  Hitts       ....  645 

Denudation  of  the  Wealdenr— Discovery  of  the  Lower  Crag  on  the  summit  of  the 
North  Downs  between  Folkestone  and  Dorking  -  645 

New  Fossil  Mammalia  from  the  Purbeck  or  Upper  Oolitic  Strata  in  Dorsetshire. 
Discovery  in  Dorsetshire  of  seven  or  eight  new  genera  of  Mammalia  in  the  Purbeck 
or  Upper  Oolite  strata — First  example  of  a  skull  of  a  Mammifer  from  Secondary 
Rocks — Insectivorous  Marsupials  and  Placentals  and  herbivorous  Marsupials — 
Figures  and  descriptions — Light  thrown  on  the  Microlestes  or  oldest  triassic  Mam- 
mifer— General  bearing  of  the  new  facts  -  -  647 

Discovery  of  Mammalian  Remains  in  Rocks  of  high  Antiquity  in]  North  Carolina, 
United  States  -  -  -  -  -  -  -  -  -  659 

Upper  Trias  of  the  Eastern  Alps. — Recognition  of  a  Marine  equivalent  of  the  Upper 
Trias  in  the  Austrian  Alps — True  position  of  the  St.  Cassian  and  Hallstatt  Beds — 
800  new  species  of  triassic  Mollusca  and  Radiata — Links  thus  supplied  for  connect- 
ing the  Palaeozoic  and  Neozoic  faunas  660 

On  the  supposed  evidence  of  Phcenogamous  Plants  (not  Gymnosperms)  in  the  Coal 
Formation  ...----_.  663 

Sihvrian  and  Cambrian  Rocks  and  M.  BarrandJs  theory  of  Colonies        -          -    664 
Antiquity  of  Fossil  Birds  -  669 


MANUAL 


OF 


ELEMENTARY  GEOLOGY. 


CHAPTER  I.  , 

ON    THE    DIFFERENT    CLASSES    OF    ROCKS. 

Geology  defined — Successive  formation  of  the  earth's  crust — Classification  d 
rocks  according  to  their  origin  and  age — Aqueous  rocks— Their  stratification 
and  imbedded  fossils — Volcanic  rocks,  with  and  without  cones  and  craters — 
Plutonic  rocks,  and  their  relation  to  the  volcanic — Metamorphic  rocks  and  their 
probable  origin — The  term  primitive,  why  erroneously  applied  to  the  crystal- 
line formations — Leading  division  of  the  work. 

OF  what  materials  is  the  earth  composed,  and  in  what  manner  are  these 
materials  arranged  ?  These  are  the  first  inquiries  with  which  Geology 
is  occupied,  a  science  which  derives  its  name  from  the  Greek  y?j,  ge,  the 
earth,  and  Xoyos,  logos,  a  discourse.  Previously  to  experience,  we  might, 
have  imagined  that  investigations  of  this  kind  would  relate  exclusively 
to  the  mineral  kingdom,  and  to  the  various  rocks,  soils,  and  metals, 
which  occur  upon  the  surface  of  the  earth,  or  at  various  depths  beneath 
it.  But,  in  pursuing  such  researches,  we  soon  find  ourselves  led  on  to 
consider  the  successive  changes  which  have  taken  place  in  the  former 
state  of  the  earth's  surface  and  interior,  and  the  causes  which  have  given 
rise  to  these  changes  ;  and,  what  is  still  more  singular  and  unexpected, 
we  soon  become  engaged  in  researches  into  the  history  of  the  animate 
creation,  or  of  the  various  tribes  of  animals  and  plants  which  have,  at 
different  periods  of  the  past,  inhabited  the  globe. 

All  are  aware  that  the  solid  parts  of  the  earth  consist  of  distinct  sub- 
stances, such  as  clay,  chalk,  sand,  limestone,  coal,  slate,  granite,  and  the 
like;  but  previously  to  observation  it  is  commonly  imagined  that  all 
these  had  remained  from  the  first  in  the  state  in  which  we  now  see 
them, — that  they  were  created  in  their  present  form,  and  in  their  present 
position.  The  geologist  soon  comes  to  a  different  conclusion,  discovering 
proofs  that  the  external  parts  of  the  earth  were  not  all  produced  in  the 
beginning  of  things,  in  the  state  in  which  we  now  behold  them,  nor  in 
an  instant  of  time.  On  the  contrary,  he  can  show  that  they  have  acquired 
their  actual  configuration  and  condition  gradually,  under  a  great  variety 


2  CLASSIFICATION  OF  ROCKS.  [On.  1 

of  circumstances,  and  at  successive  periods,  during  each  of  which  distinct 
races  of  living  beings  have  flourished  on  the  land  and  in  the  waters,  the 
remains  of  these  creatures  still  lying  buried  in  the  crust  of  the  earth. 

By  the  "  earth's  crust,"  is  meant  that  small  portion  of  the  exterior  of 
our  planet  which  is  accessible  to  human  observation,  or  on  which  we  are 
enabled  to  reason  by  observations  made  at  or  near  the  surface.  These 
reasonings  may  extend  to  a  depth  of  several  miles,  perhaps  ten  miles  ; 
and  even  then  it  may  be  said,  that  such  a  thickness  is  no  more  than  ^^ 
part  of  the  distance  from  the  surface  to  the  centre.  The  remark  is  just ; 
but  although  the  dimensions  of  such  a  crust  are,  in  truth,  insignificant 
when  compared  to  the  entire  globe,  yet  they  are  vast,  and  of  magnificent 
extent  in*  relation  to  man,  and  to  the  organic  beings  which  people  our 
lc£iob^"'  •  inferring  to  this  standard  of  magnitude,  the  geologist  may 
admire  tfye  «Cmple  limits  of  his  domain,  and  admit,  at  the  same  time, 
l<tkfet  ndt/oijty. /he  exterior  of  the  planet,  but  the  entire  earth,  is  but  an 
atom  in  the  midst  of  the  countless  worlds  surveyed  by  the  astronomer. 

The  materials  of  this  crust  are  not  thrown  together  confusedly ;  but 
distinct  mineral  masses,  called  rocks,  are  found  to  occupy  definite  space», 
and  to  exhibit  a  certain  order  of  arrangement.  The  term  rock  is  applied 
indifferently  by  geologists  to  all  these  substances,  whether  they  be  soft  or 
stony,  for  clay  and  sand  are  included  in  the  term,  and  some  have  even 
brought  peat  under  this  denomination.  Our  older  writers  endeavored 
to  avoid  offering  such  violence  to  our  language,  by  speaking  of  the  com- 
ponent materials  of  the  earth  as  consisting  of  rocks  and  soils.  But  there 
is  often  so  insensible  a  passage  from  a  soft  and  incoherent  state  to  that 
of  stone,  that  geologists  of  all  countries  have  found  it  indispensable  to 
have  one  technical  term  to  include  both,  and  in  this  sense  we  find  roche 
applied  in  French,  rocca  in  Italian,  andfelsart  in  German.  The  beginner, 
however,  must  constantly  bear  in  mind,  that  the  term  rock  by  no  means 
implies  that  a  mineral  mass  is  in  an  indurated  or  stony  condition. 

The  most  natural  and  convenient  mode  of  classifying  the  various  rocks 
which  compose  the  earth's  crust,  is  to  refer,  in  the  first  place,  to  their 
origin,  and  in  the  second  to  their  relative  age.  I  shall  therefore  begin 
by  endeavoring  briefly  to  explain  to  the  student  how  all  rocks  may  be 
divided  into  four  great  classes  by  reference  to  their  different  origin,  or,  in 
other  words,  by  reference  to  the  different  circumstances  and  causes  by 
which  they  have  been  produced. 

The  first  two  divisions,  which  will  at  once  be  understood  as  natural, 
are  the  aqueous  and  volcanic,  or  the  products  of  watery  and  those  of 
igneous  action  at  or  near  the  surface. 

Aqueous  rocks. — The  aqueous  rocks,  sometimes  called  the  sedimentary, 
or  fossiliferous,  cover  a  larger  part  of  the  earth's  surface  than  any  others. 
These  rocks  are  stratified,  or  divided  into  distinct  layers,  or  strata.  The 
term  stratum  means  simply  a  bed,  or  any  thing  spread  out  or  strewed 
over  a  given  surface  ;  and  we  infer  that  these  strata  have  been  generally 
spread  out  by  the  action  of  water,  from  what  we  daily  see  taking  place 
near  the  mouths  of  rivers,  or  on  the  land  during  temporary  inundations. 


CH.  I.]  AQUEOUS   ROCKS.  3 

For,  whenever  a  running  stream  charged  with  mud  or  sand,  has  its  ve- 
locity checked,  as  when  it  enters  a  lake  or  sea,  or  overflows  a  plain,  the 
sediment,  previously  held  in  suspension  by  the  motion  of  the  water 
sinks,  by  its  own  gravity,  to  the  bottom.  In  this  manner  layers  of  mud 
and  sand  are  thrown  down  one  upon  another. 

If  we  drain  a  lake  which  has  been  fed  by  a  small  stream,  we  frequently 
find  at  the  bottom  a  series  of  deposits,  disposed  with  considerable  regu- 
larity, one  above  the  other ;  the  uppermost,  perhaps,  may  be  a  stratum 
of  peat,  next  below  a  more  dense  and  solid  variety  of  the  same  material ; 
still  lower  a  bed  of  shell-marl,  alternating  with  peat  or  sand,  and  then 
other  beds  of  marl,  divided  by  layers  of  clay.  Now,  if  a  second  pit  be 
sunk  through  the  same  continuous  lacustrine  formation,  at  some  distance 
from  the  first,  nearly  the  same  series  of  beds  is  commonly  met  with,  yet 
with  slight  variations  ;  some,  for  example,  of  the  layers  of  sand,  clay,  or 
marl,  may  be  wanting,  one  or  more  of  them  having  thinned  out  and 
given  place  to  others,  or  sometimes  one  of  the  masses  first  examined  is 
observed  to  increase  in  thickness  to  the  exclusion  of  other  beds. 

The  term  "formation"  which  I  have  used  in  the  above  explanation, 
expresses  in  geology  any  assemblage  of  rocks  which  have  some  character 
in  common,  whether  of  origin,  age,  or  composition.  Thus  we  speak  of 
stratified  and  unstratified,  freshwater  and  marine,  aqueous  and  volcanic, 
ancient  and  modern,  metalliferous  and  non-metalliferous  formations. 

In  the  estuaries  of  large  rivers,  such  as  the  Ganges  and  the  Mississippi, 
we  may  observe,  at  low  water,  phenomena  analogous  to  those  of  the 
drained  lakes  above  mentioned,  but  on  a  grander  scale,  and  extending 
over  areas  several  hundred  miles  in  length  and  breadth.  When  the  pe- 
riodical inundations  subside,  the  river  hollows  out  a  channel  to  the  depth 
of  many  yards  through  horizontal  beds  of  clay  and  sand,  the  ends  of 
which  are  seen  exposed  in  perpendicular  cliffs.  These  beds  vary  in  their 
mineral  composition,  or  color,  or  in  the  fineness  or  coarseness  of  their 
particles,  and  some  of  them  are  occasionally  characterized  by  containing 
drift-wood.  At  the  junction  of  the  river  and  the  sea,  especially  in  la- 
goons nearly  separated  by  sand-bars  from  the  ocean,  deposits  are  often 
formed  in  which  brackish-water  and  salt-water  shells  are  included. 

The  annual  floods  of  the  Nile  in  Egypt  are  well  known,  and  the  fertile 
deposits  of  mud  which  they  leave  on  the  plains.  This  mud  is  stratified, 
the  thin  layer  thrown  down  in  one  season  differing  slightly  in  color  from 
that  of  a  previous  year,  and  being  separable  from  it,  as  has  been  observed 
in  excavations  at  Cairo,  and  other  places.* 

When  beds  of  sand,  clay,  and  marl,  containing  shells  and  vegetable 
matter,  are  found  arranged  in  a  similar  manner  in  the  interior  of  the 
earth,  we  ascribe  to  them  a  similar  origin ;  and  the  more  we  examine 
their  characters  in  minute  detail,  the  more  exact  do  we  find  the  resem- 
blance. Thus,  for  example,  at  various  heights  and  depths  in  the  earth, 
and  often  far  from  seas,  lakes,  and  rivers,  we  meet  with  layers  of  rounded 

*  See  Principles  of  Geology,  by  the  Author,  Index,  "Nile,"  "  Eiv-ers,"  <tc. 


4  AQUEOUS  ROCKS.  [Ca.  1. 

pebbles  composed  of  flint,  limestone,  granite,  or  other  rocks,  resembling 
the  shingles  of  a  sea-beach  or  the  gravel  in  a  torrent's  bed.  Such  layers 
of  pebbles  frequently  alternate  with  others  formed  of  sand  or  fine  sedi- 
ment, just  as  we  may  see  in  the  channel  of  a  river  descending  from  hills 
bordering  a  coast,  where  the  current  sweeps  down  at  one  season  coarse 
sand  and  gravel,  while  at  another,  when  the  waters  are  low  and  less  rapid, 
fine  mud  and  sand  alone  are  carried  seaward.* 

If  a  stratified  arrangement,  and  the  rounded  form  of  pebbles,  are  alone 
sufficient  to  lead  us  to  the  conclusion  that  certain  rocks  originated  under 
water,  this  opinion  is  farther  confirmed  by  the  distinct  and  independent 
evidence  of  fossils,  so  abundantly  included  in  the  earth's  crust.  By  a 
fossil  is  meant  any  body,  or  the  traces  of  the  existence  of  any  body, 
whether  animal  or  vegetable,  which  has  been  buried  in  the  earth  by 
natural  causes.  Now  the  remains  of  animals,  especially  of  aquatic  species, 
are  found  almost  everywhere  imbedded  in  stratified,  rocks,  and  sometimes, 
in  the  case  of  limestone,  they  are  in  such  abundance  as  to  constitute  the 
entire  mass  of  the  rock  itself.  Shells  and  corals  are  the  most  frequent, 
and  with  them  are  often  associated  the  bones  and  teeth  of  fishes,  frag- 
ments of  wood,  impressions  of  leaves,  and  other  organic  substances.  Fossil 
shells,  of  forms  such  as  now  abound  in  the  sea,  are  met  with  far  inland, 
both  near  the  surface,  and  at  great  depths  below  it.  They  occur  at  all 
heights  above  the  level  of  the  ocean,  having  been  observed  at  elevations 
of  more  than  8000  feet  in  the  Pyrenees,  10,000  in  the  Alps,  13,000  in 
the  Andes,  and  above  18,000  feet  in  the  Himalaya.! 

These  shells  belong  mostly  to  marine  testacea,  but  in  some  places 
exclusively  to  forms  characteristic  of  lakes  and  rivers.  Hence  it  is  con- 
cluded that  some  ancient  strata  were  deposited  at  the  bottom  of  the  sea, 
and  others  in  lakes  and  estuaries. 

When  geology  was  first  cultivated,  it  was  a  general  belief,  that  these 
marine  shells  and  other  fossils  were  the  effects  and  proofs  of  the  deluge 
of  Noah ;  but  all  who  have  carefully  investigated  the  phenomena  have 
long  rejected  this  doctrine.  A  transient  flood  might  be  supposed  to  leave 
behind  it,  here  and  there  upon  the  surface,  scattered  heaps  of  mud,  sand, 
and  shingle,  with  shells  confusedly  intermixed  ;  but  the  strata  containing 
fossils  are  not  superficial  deposits,  and  do  not  simply  cover  the  earth,  but 
constitute  the  entire  mass  of  mountains.  Nor  are  the  fossils  mingled 
without  reference  to  the  original  habits  and  natures  of  the  creatures  of 
which  they  are  the  memorials ;  those,  for  example,  being  found  associated 
together  which  lived  in  deep  or  in  shallow  water,  near  the  shore  or  far 
from  it,  in  brackish  or  in  salt  water. 

It  has,  moreover,  been  a  favorite  notion  of  some  modern  writers,  who 
were  aware  that  fossil  bodies  could  not  all  be  referred  to  the  deluge, 
that  they,  and  the  strata  in  which  they  are  entombed,  might  have  been 
deposited  in  the  bed  of  the  ocean  during  the  period  which  intervened 

»  See  p.  18,  fig.  7. 

f  Capt.  R.  J.  Strachey  found  oolitic  fossils  18,400  feet  high  in  the  Himalaya. 


CH.  I]  VOLCANIC   ROCKS.  5 

between  the  creation  of  man  and  the  deluge.  They  have  imagined 
that  the  antediluvian  bed  of  the  ocean,  after  having  been  the  receptacle 
of  many  stratified  deposits,  became  converted,  at  the  time  of  the  flood, 
into  the  lands  which  we  inhabit,  and  that  the  ancient  continents  were  at 
the  same  time  submerged,  and  became  the  bed  of  the  present  seas. 
This  hypothesis,  although  preferable  to  the  diluvial  theory  before  alluded 
to,  since  it  admits  that  all  fossiliferous  strata  were  successively  thrown 
down  from  water,  is  yet  wholly  inadequate  to  explain  the  repeated  revo- 
lutions which  the  earth  has  undergone,  and  the  signs  which  the  existing 
continents  exhibit,  in  most  regions,  of  having  emerged  from  the  ocean  at 
an  era  far  more  remote  than  four  thousand  years  from  the  present  time. 
Ample  proofs  of  these  reiterated  revolutions  will  be  given  in  the  sequel, 
and  it  will  be  seen  that  many  distinct  sets  of  se  limentary  strata,  hundreds 
and  sometimes  thousands  of  feet  thick,  are  piled  one  upon  the  other  in 
the  earth's  crust,  each  containing  peculiar  fossil  animals  and  plants  of 
species  distinguishable  for  the  most  part  from  all  those  now  living. 
The  mass  of  some  of  these  strata  consists  almost  entirely  of  corals,  others 
are  made  up  of  shells,  others  of  plants  turned  into  coal,  while  some  are 
without  fossils.  In  one  set  of  strata  the  species  of  fossils  are  marine ; 
in  another,  lying  immediately  above  or  below,  they  as  clearly  prove 
that  the  deposit  was  formed  in  a  lake  or  brackish  estuary.  When  the 
student  has  more  fully  examined  into  these  appearances,  he  will  become 
convinced  that  the  time  required  for  the  origin  of  the  rocks  composing 
the  actual  continents  must  have  been  far  greater  than  that  which  is  con- 
ceded by  the  theory  above  alluded  to ;  and  likewise  that  no  one 
universal  and  sudden  conversion  of  sea  into  land  will  account  for  geo- 
logical appearances. 

We  have  now  pointed  out  one  great  class  of  rocks,  which,  however 
they  may  vary  in  mineral  composition,  color,  grain,  or  other  characters, 
external  and  internal,  may  nevertheless  be  grouped  together  as  having  a 
common  origin.  They  have  all  been  formed  under  water,  in  the  same 
manner  as  modern  accumulations  of  sand,  mud,  shingle,  banks  of  shells, 
reefs  of  coral,  and  the  like,  and  are  all  characterized  by  stratification  or 
fossils,  or  by  both. 

Volcanic  rocks. — The  division  of  rocks  which  we  may  next  consider 
are  the  volcanic,  or  those  which  have  been  produced  at  or  near  the  sur- 
face whether  in  ancient  or  modern  times,  not  by  water,  but  by  the  action 
of  fire  or  subterranean  heat.  These  rocks  are  for  the  most  part  unstrat- 
ified,  and  are  devoid  of  fossils.  They  are  more  partially  distributed  than 
aqueous  formations,  at  least  in  respect  to  horizontal  extension.  Among 
those  parts  of  Europe  where  they  exhibit  characters  not  to  be  mistaken, 
I  may  mention  not  only  Sicily  and  the  country  round  Naples,  but  Au- 
vergne,  Velay,  and  Vivarais,  now  the  departments  of  Puy  de  Dome, 
Haute  Loire,  and  Ard6che,  towards  the  centre  and  south  of  France,  in 
which  are  several  hundred  conical  hills  having  the  forms  of  modern  vol- 
canoes, with  craters  more  or  less  perfect  on  many  of  their  summits.  These 
cones  are  composed  moreover  of  lava,  sand,  and  ashes,  similar  to  those 


6  VOLCANIC  ROCKS.  [CH,  1 

of  active  volcanoes.  Streams  of  lava  may  sometimes  be  tiaced  from  the 
cones  into  the  adjoining  valleys,  where  they  have  choked  up  the  ancient 
channels  of  rivers  with  solid  rock,  in  the  same  manner  as  some  modern 
flows  of  lava  in  Iceland  have  been  known  to  do,  the  rivers  either  flowing 
beneath  or  cutting  out  a  narrow  passage  on  one  side  of  the  lava.  Al- 
though none  of  these  French  volcanoes  have  been  in  activity  within  the 
period  of  history  or  tradition,  their  forms  are  often  very  perfect.  Some, 
however,  have  been  compared  to  the  mere  skeletons  of  volcanoes,  the 
rains  and  torrents  having  washed  their  sides,  and  removed  all  the  loose 
sand  and  scoriae,  leaving  only  the  harder  and  more  solid  materials.  By 
this  erosion,  and  by  earthquakes,  their  internal  structure  has  occasionally 
been  laid  open  to  view,  in  fissures  and  ravines  ;  and  we  then  behold  not 
only  many  successive  beds  and  masses  of  porous  lava,  sand,  and  scoriae, 
but  also  perpendicular  walls,  or  dikes,  as  they  are  called,  of  vo'canic 
rock,  which  have  burst  through  the  other  materials.  Such  dikes  are 
also  observed  in  the  structure  of  Vesuvius,  Etna,  and  other  active 
volcanoes.  They  have  been  formed  by  the  pouring  of  melted  matter, 
whether  from  above  or  below,  into  open  fissures,  and  they  commonly 
traverse  deposits  of  volcanic  tuff,  a  substance  produced  by  the  show- 
ering down  from  the  air,  or  incumbent  waters,  of  sand  and  cinders, 
first  shot  up  from  the  interior  of  the  earth  by  the  explosions  of  volcanic 


Besides  the  parts  of  France  above  alluded  to,  there  are  other  countries, 
as  the  north  of  Spain,  the  south  of  Sicily,  the  Tuscan  territory  of  Italy, 
the  lower  Rhenish  provinces,  and  Hungary,  where  spent  volcanoes  may 
be  seen,  still  preserving  in  many  cases  a  conical  form,  and  having  craters 
and  often  lava-streams  connected  with  them. 

There  are  also  other  rocks  in  England,  Scotland,  Ireland,  and  almost 
every  country  in  Europe,  which  we  infer  to  be  of  igneous  origin,  although 
they  do  not  form  hills  with  cones  and  craters.  Thus,  for  example,  we 
feel  assured  that  the  rock  of  Staffa,  and  that  of  the  Giants'  Causeway, 
called  basalt,  is  volcanic,  because  it  agrees  in  its  columnar  structure  and 
mineral  composition  with  streams  of  lava  which  we  know  to  have  flowed 
from  the  craters  of  volcanoes.  We  find  also  similar  basaltic  and  other 
igneous  rocks  associated  with  beds  of  tuff  in  various  parts  of  the  British 
Isles,  and  forming  dikes,  such  as  have  been  spoken  of ;  and  some  of  the 
strata  through  which  these  dikes  cut  are  occasionally  altered  at  the 
point  of  contact,  as  if  they  had  been  exposed  to  the  intense  heat  of 
melted  matter. 

The  absence  of  cones  and  craters,  and  long  narrow  streams  of  super- 
ficial lava,  in  England  and  many  other  countries,  is  principally  to  be 
attributed  to  the  eruptions  having  been  submarine,  just  as  a  considerable 
proportion  of  volcanoes  in  our  own  times  burst  out  beneath  the  sea. 
But  this  question  must  be  enlarged  upon  more  fully  in  the  chapters  on 
Igneous  Rocks,  in  which  it  will  also  be  shown,  that  as  different  sedi- 
mentary formations,  containing  each  their  characteristic  fossils,  have 
been  deposited  at  successive  periods,  so  also  volcanic  sand  and  scoria? 


Ce.  I]  PLUTONIC   ROCKS.  7 

have  been  thrown  out,  and  lavas  have  flowed  over  the  land  or  bed  of  the 
sea,  at  many  different  epochs,  or  have  been  injected  into  fissures;  so  that 
the  igneous  as  well  as  the  aqueous  rocks  may  be  classed  as  a  chronologi- 
cal series  of  monuments,  throwing  light  on  a  succession  of  events  in  the 
history  of  the  earth. 

Plutonic  rocks  (Granite,  &c.). — We  have  now  pointed  out  the  exist- 
ence of  two  distinct  orders  of  mineral  masses,  the  aqueous  and  the 
volcanic  :  but  if  we  examine  a  large  portion  of  a  continent,  especially  if 
it  contain  within"  it  a  lofty  mountain  range,  we  rarely  fail  to  discover 
two  other  classes  of  rocks,  very  distinct  from  either  of  those  above 
alluded  to,  and  which  we  can  neither  assimilate  to  deposits  such  as 
are  now  accumulated  in  lakes  or  seas,  nor  to  those  generated  by 
ordinary  volcanic  action.  The  members  of  both  these  divisions  of 
rocks  agree  in  being  highly  crystalline  and  destitute  of  organic  remains. 
The  rocks  of  one  division  have  been  called  plutonic,  comprehending 
all  the  granites  and  certain  porphyries,  which  are  nearly  jrilied  in 
some  of  their  characters  to  volcanic  formations.  The  members  of  the 
other  class  are  stratified  and  often  slaty,  and  have  been  called  by 
some  the  crystalline  schists,  in  which  group  are  included  gneiss, 
micaceous-schist  (or  mica-slate),  hornblende-schist,  statuary  marble, 
the  finer  kinds  of  roofing  slate,  and  other  rocks  afterwards  to  be 
described. 

As  it  is  admitted  that  nothing  strictly  analogous  to  these  crystalline 
productions  can  now  be  seen  in  the  progress  of  formation  on  the  earth's 
surface,  it  will  naturally  be  asked,  on  what  data  we  can  find  a  place  for 
them  in  a  system  of  classification  founded  on  the  origin  of  rocks.  I 
cannot,  in  reply  to  this  question,  pretend  to  give  the  student,  in  a  few 
words,  an  intelligible  account  of  the  long  chain  of  facts  and  reasonings 
by  which  geologists  have  been  led  to  infer  the  analogy  of  the  rocks  in 
question  to  others  now  in  progress  at  the  surface.  The  result,  however, 
may  be  briefly  stated.  All  the  various  kinds  of  granite,  which  consti- 
tute the  plutonic  family,  are  supposed  to  be  of  igneous  origin,  but  to 
have  been  formed  under  great  pressure,  at  a  considerable  depth  in  the 
earth,  or  sometimes,  perhaps,  under  a  certain  weight  of  incumbent 
water.  Like  the  lava  of  volcanoes,  they  have  been  melted,  and  have 
afterwards  cooled  and  crystallized,  but  with  extreme  slowness,  and  under 
conditions  very  different  from  those  of  bodies  cooling  in  the  open  air. 
Hence  they  differ  from  the  volcanic  rocks,  not  only  by  their  more  crys- 
talline texture,  but  also  by  the  absence  of  tuffs  and  breccias,  which  are 
the  products  of  eruptions  at  the  earth's  surface,  or  beneath  seas  of 
inconsiderable  depth.  They  differ  also  by  the  absence  of  pores  or  cel- 
lular cavities,  to  which  the  expansion  of  the  entangled  gases  gives  rise 
in  ordinary  lava. 

Although  granite  has  often  pierced  through  other  strata,  it  has  rarely, 
if  ever,  been  observed  to  rest  upon  them,  as  if  it  had  overflowed.  But 
as  this  is  continually  the  case  with  the  volcanic  rocks,  they  have 
been  styled,  from  this  peculiarity,  "  overlying"  by  Dr.  MacCulloch ; 


3  METAMOEPHIC  ROCKS.  [Ca  1 

and  Mr.  Necker  has  proposed  the  term  "  underlying"  for  the  granites, 
to  designate  the  opposite  mode  in  which  they  almost  invariably  present 
themselves. 

Metamorphic,  or  stratified  crystalline  rocks. — The  fourth  and  last 
great  division  of  rocks  are  the  crystalline  strata  and  slates,  or  schists, 
called  gneiss,  mica-schist,  clay-slate,  chlorite-schist,  marble,  and  the  like, 
the  origin  of  which  is  more  doubtful  than  that  of  the  other  three 
classes.  They  contain  no  pebbles,  or  sand,  or  scoriae,  or  angular  pieces 
of  imbedded  stone,  and  no  traces  of  organic  bodies,  and  they  are  often 
as  crystalline  as  granite,  yet  are  divided  into  beds,  corresponding  in 
form  and  arrangement  to  those  of  sedimentary  formations,  and  are 
therefore  said  to  be  stratified.  The  beds  sometimes  consist  of  an  alter- 
nation of  substances  varying  in  color,  composition,  and  thickness,  pre- 
cisely as  we  see  in  stratified  fossiliferous  deposits.  According  to  the 
Huttonian  theory,  which  I  adopt  as  the  most  probable,  and  which  will  be 
afterwards  more  fully  explained,  the  materials  of  these  strata  were  origi- 
nally deposited  from  water  in  the  usual  form  of  sediment,  but  they  were 
subsequently  so  altered  by  subterranean  heat,  as  to  assume  a  new  texture. 
It  is  demonstrable,  in  some  cases  at  least,  that  such  a  complete  conversion 
has  actually  taken  place,  fossiliferous  strata  laving  exchanged  an  earthy  for 
a  highly  crystalline  texture  for  a  distance  of  a  quarter  of  a  mile  from  their 
contact  with  granite.  In  some  cases,  dark  limestones  replete  with  shells  and 
corals,  have  been  turned  into  white  statuary  marble,  and  hard  clays,  contain- 
ing vegetable  or  other  remains,  into  slates  called  mica-schist  or  hornblende- 
schist,  every  vestige  of  the  organic  bodies  having  been  obliterated. 

Although  we  are  in  a  great  degree  ignorant  of  the  precise  nature  of 
the  influence  exerted  in  these  cases,  yet  it  evidently  bears  some  analogy 
to  that  which  volcanic  heat  and  gases  are  known  to  produce ;  and  the 
action  may  be  conveniently  called  plutonic,  because  it  appears  to  have 
been  developed  in  those  regions  where  plutonic  rocks  are  generated,  and 
under  similar  circumstances  of  pressure  and  depth  in  the  earth.  Whether 
hot  water  or  steam  permeating  stratified  masses,  or  electricity,  or  any 
other  causes  have  cooperated  to  produce  the  crystalline  texture,  may  be 
matter  of  speculation,  but  it  is  clear  that  the  plutonic  influence  has  some- 
times pervaded  entire  mountain  masses  of  strata. 

In  accordance  with  the  hypothesis  above  alluded  to,  I  proposed  in  the 
first  edition  of  the  Principles  of  Geology  (1833)^  the  term  "  Metamorphic" 
for  the  altered  strata,  a  term  derived  from  juosra,  meta,  trans,  and  fAopptj, 
morphe,/oma. 

Hence  there  are  four  great  classes  of  rocks  considered  in  reference  to  their 
origin, — the  aqueous,  the  volcanic,  the  plutonic,  and  the  metamorphic.  lu 
the  course  of  this  work  it  will  be  shown,  that  portions  of  each  of  these  four 
distinct  classes  have  originated  at  many  successive  periods.  They  have  all 
been  produced  contemporaneously,  and  may  even  now  be  in  the  progress 
of  formation  on  a  large  scale.  It  is  not  true,  as  was  formerly  supposed, 
that  all  granites,  together  with  the  crystalline  or  metamorphic  strata, 
were  first  formed,  and  therefore  entitled  to  be  called  "  primitive,"  and 


CH.  I]         FOUK   CLASSES   OP  KOCKS   COXTEMPOKANEOUS.  9 

that  the  aqueous  and  volcanic  rocks  were  afterwards  superimposed,  and 
should,  therefore,  rank  as  secondary  in  the  order  of  time.  This  idea 
was  adopted  in  the  infancy  of  the  science,  when  all  formations,  whether 
stratified  or  unstratified,  earthy  or  crystalline,  with  or  without  fossils, 
were  alike  regarded  as  of  aqueous  origin.  At  that  period  it  was  natu- 
rally argued,  that  the  foundation  must  be  older  than  the  superstructure ; 
but  it  was  afterwards  discovered,  that  this  opinion  was  by  no  means  in 
every  instance  a  legitimate  deduction  from  facts  ;  for  the  inferior  parts 
of  the  earth's  crust  have  often  been  modified,  and  even  entirely  changed, 
by  the  influence  of  volcanic  and  other  subterranean  causes,  while  super- 
imposed formations  have  not  been  in  the  slightest  degree  altered.  In 
other  words,  the  destroying  and  renovating  processes  have  given  birth 
to  new  rocks  below,  while  those  above,  whether  crystalline  or  fossllif- 
erous,  have  remained  in  their  ancient  condition.  Even  in  cities,  such  as 
Venice  and  Amsterdam,  it  cannot  be  laid  down  as  universally  true,  that 
the  upper  parts  of  each  edifice,  whether  of  brick  or  marble,  are  more 
modern  than  the  foundations  on  which  they  rest,  for  these  often  consist 
of  wooden  piles,  which  may  have  rotted  and  been  replaced  one  after 
the  other,  without  the  least  injury  to  the  buildings  above ;  meanwhile, 
these  may  have  required  scarcely  any  repair,  and  may  have  been  con- 
stantly inhabited.  So  it  is  with  the  habitable  surface  of  our  globe,  in 
its  relation  to  large  masses  of  rock  immediately  below  :  it  may  continue 
the  same  for  ages,  while  subjacent  materials,  at  a  great  depth,  are  passing 
from  a  solid  to  a  fluid  state,  and  then  reconsolidating,  so  as  to  acquire  a 
new  texture. 

As  all  the  crystalline  rocks  may,  in  some  respects,  be  viewed  as  be- 
longing to  one  great  family,  whether  they  be  stratified  or  unstratified, 
plutonic  or  metamorphic,  it  will  often  be  convenient  to  speak  of  them  by 
one  common  name.  It  being  now  ascertained,  as  above  stated,  that  they 
are  of  very  different  ages,  sometimes  newer  than  the  strata  called  second- 
ary, the  terms  primitive  and  primary,  which  were  formerly  used  for  the 
whole,  must  be  abandoned,  as  they  would  imply  a  manifest  contradiction. 
It  is  indispensable,  therefore,  to  find  a  new  name,  one  which  must  not  be 
of  chronological  import,  and  must  express,  on  the  one  hand,  some  pecu- 
liarity equally  attributable  to  granite  and  gneiss  (to  the  plutonic  as  well 
as  the  altered  rocks),  and,  on  the  other,  must  have  reference  to  characters 
in  which  those  rocks  differ,  both  from  the  volcanic  and  from  the  unal- 
tered sedimentary  strata.  I  proposed  in  the  Principles  of  Geology  (first 
edition,  vol.  iii.),  the  term  "  hypogene"  for  this  purpose,  derived  from 
utfo,  under,  and  yivofxai,  to  be,  or  to  be  born /  a  word  implying  the 
theory  that  granite,  gneiss,  and  the  other  crystalline  formations  are  alike 
nether-formed  rocks,  or  rocks  which  have  not  assumed  their  present 
/orm  and  structure  at  the  surface.  They  occupy  the  lowest  place  in 
the  order  of  superposition.  Even  in  regions  such  as  the  Alps,  where 
some  masses  of  granite  and  gneiss  can  be  shown  to  be  of  comparatively 
modern  date,  belonging,  for  example,  to  the  period  hereafter  to  be 
described  as  tertiary,  they  are  still  underlying  rocks.  They  never  repose 


10  COMPONENTS  OF  STKATA.  [Cir.  II 

on  the  volcanic  or  trappean  formations,  nor  on  strata  containing  organic 
remains.  They  are  hypogene,  as  "  being  under"  all  the  rest. 

From  what  has  now  been  said,  the  reader  will  understand  that  each 
of  the  four  great  classes  of  rocks  may  be  studied  under  two  distinct 
points  of  view  ;  first,  they  may  be  studied  simply  as  mineral  masses  de- 
riving their  origin  from  particular  causes,  and  having  a  certain  composi- 
tion, form,  and  position  in  the  earth's  crust,  or  other  characters  both 
positive  and  negative,  such  as  the  presence  or  absence  of  organic  re- 
mains. In  the  second  place,  the  rocks  of  each  class  may  be  viewed  as 
a  grand  chronological  series  of  monuments,  attesting  a  succession  of 
events  in  the  former  history  of  the  globe  and  its  living  inhabitants. 

I  shall  accordingly  proceed  to  treat  of  each  family  of  rocks  ;  first,  in 
reference  to  those  characters  which  are  not  chronological,  and  then  in 
particular  relation  to  the  several  periods  when  they  were  formed. 


CHAPTER  II. 

AQUEOUS    ROCKS — THEIR    COMPOSITION    AND    FORMS    OF    STRATIFI- 
CATION. 

Mineral  composition  of  strata — Arenaceous  rocks — Argillaceous — Calcareous — 
Gypsum — Forms  of  stratification — Original  horizontally — Thinning  out — Diag- 
onal arrangement— Ripple  mark. 

IN  pursuance  of  the  arrangement  explained  in  the  last  chapter,  we  shall 
begin  by  examining  the  aqueous  or  sedimentary  rocks,  which  are  for 
the  most  part  distinctly  stratified,  and  contain  fossils.  We  may  first 
study  them  with  reference  to  their  mineral  composition,  external  appear- 
ance, position,  mode  of  origin,  organic  contents,  and  other  characters 
which  belong  to  them  as  aqueous  formations,  independently  of  their  age, 
and  we  may  afterwards  consider  them  chronologically  or  with  reference 
to  the  successive  geological  periods  when  they  originated. 

I  have  already  given  an  outline  of  the  data  which  led  to  the  belid 
that  the  stratified  and  fossiliferous  rocks  were  originally  deposited  under 
water ;  but,  before  entering  into  a  more  detailed  investigation,  it  will  be 
desirable  to  say  something  of  the  ordinary  materials  of  which  such 
strata  are  composed.  These  may  be  said  to  belong  principally  to  three 
divisions,  the  arenaceous,  the  argillaceous,  and  the  calcareous,  which  are 
formed  respectively  of  sand,  clay,  and  carbonate  of  lime.  Of  these,  the 
arenaceous,  or  sandy  masses,  are  chiefly  made  up  of  siliceous  or  flinty 
grains ;  the  argillaceous,  or  clayey,  of  a  mixture  of  siliceous  matter, 
with  a  certain  proportion,  about  a  fourth  in  weight,  of  aluminous  earth ; 


CH.  II.]     MINERAL  COMPOSITION  OF  STRATIFIED  ROCKS.  11 

and,  lastly,  the  calcareous  rocks  or  limestones  consist  of  carbonic  acid 
and  lime. 

Arenaceous  or  siliceous  rocks. — To  speak  first  of  the  sandy  division  : 
beds  of  loose  sand  are  frequently  met  with,  of  which  the  grains  consist 
entirely  of  silex,  which  term  comprehends  all  purely  siliceous  minerals, 
as  quartz  and  common  flint.  Quartz  is  silex  in  its  purest  form ;  flint 
usually  contains  some  admixture  of  alumine  and  oxide  of  iron.  The 
siliceous  grains  in  sand  are  usually  rounded,  as  if  by  the  action  of  running 
water.  Sandstone  is  an  aggregate  of  such  grains,  which  often  cohere  to- 
gether without  any  visible  cement,  but  more  commonly  are  bound  together 
by  a  slight  quantity  of  siliceous  or  calcareous  matter,  or  by  iron  or  clay. 

Pure  siliceous  rocks  may  be  known  by  not  effervescing  when  a  drop 
of  nitric,  sulphuric,  or  other  acid  is  applied  to  them,  or  by  the  grains 
not  being  readily  scratched  or  broken  by  ordinary  pressure.  In  nature 
there  is  every  intermediate  gradation,  from  perfectly  loose  sand,  to  the 
hardest  sandstone.  In  micaceous  sandstones  mica  is  very  abundant; 
and  the  thin  silvery  plates  into  which  that  mineral  divides,  are  often  ar- 
ranged in  layers  parallel  to  the  planes  of  stratification,  giving  a  slaty  or 
laminated  texture  to  the  rock. 

When  sandstone  is  coarse-grained,  it  is  usually  called  grit.  If  the 
grains  are  rounded,  and  large  enough  to  be  called  pebbles,  it  becomes  a 
conglomerate,  or  pudding-stone,  which  may  consist  of  pieces  of  one  or  of 
many  different  kinds  of  rock.  A  conglomerate,  therefore,  is  simply 
gravel  bound  together  by  a  cement. 

Argillaceous  rocks. — Clay,  strictly  speaking,  is  a  mixture  of  silex  or 
flint  with  a  large  proportion,  usually  about  one-fourth,  of  alumine,  or 
argil ;  but,  in  common  language,  any  earth  which  possesses  sufficient 
ductility,  when  kneaded  up  with  water,  to  be  fashioned  like  paste  by 
the  hand,  or  by  the  potter's  lathe,  is  called  a  clay  ;  and  such  clays  vary 
greatly  in  their  composition,  and  are,  in  general,  nothing  more  than  mud 
derived  from  the  decomposition  or  wearing  down  of  rocks.  The  purest 
clay  found  in  nature  is  porcelain  clay,  or  kaolin,  which  results  from  the 
decomposition  of  a  rock  composed  of  felspar  and  quartz,  and  it  is  almost 
always  mixed  with  quartz.*  Shale  has  also  the  property,  like  clay,  of 
becoming  plastic  in  water :  it  is  a  more  solid  form  of  clay,  or  argillaceous 
matter,  condensed  by  pressure.  It  usually  divides  into  laminae,  more  or 
less  regular. 

One  general  character  of  all  argillaceous  rocks  is  to  give  out  a  pe- 
culiar, earthy  odor  when  breathed  upon,  which  is  a  test  of  the  presence 
of  alumine,  although  it  does  not  belong  to  pure  alumine,  but,  apparently, 
to  the  combination  of  that  substance  with  oxide  of  iron.f 

*  The  kaolin  of  China  consists  of  Tl'15  parts  of  silex,  15'86  of  alumine,  T92  of 
lime,  and  6'?3  of  water  (W.  Phillips,  Mineralogy,  p.  33) ;  but  other  porcelain  clays 
differ  materially,  that  of  Cornwall  being  composed,  according  to  Boase,  of  nearly 
equal  parts  of  silica  and  alumine,  with  1  per  cent,  of  magnesia.  (Phil.  Mag.  voL 
x.  1837.) 

f  See  W.  Phillips's  Mineralogy,  "  Alumine." 


12  MINERAL   COMPOSITION  OF  STRATIFIED   ROCKS.         [On.  11 

Calcareous  rocks. — This  division  comprehends  those  rocks  which,  like 
chalk,  are  composed  chiefly  of  lime  and  carbonic  acid.  Shells  and  corals 
are  also  formed  of  the  same  elements,  with  the  addition  of  animal  matter. 
To  obtain  pure  lime  it  is  necessary  to  calcine  these  calcareous  substances, 
that  is  to  say,  to  expose  them  to  heat  of  sufficient  intensity  to  drive  off 
the  carbonic  acid,  and  other  volatile  matter.  White  chalk  is  sometimes 
pure  carbonate  of  lime ;  and  this  rock,  although  usually  in  a  soft  and 
earthy  state,  is  occasionally  sufficiently  solid  to  be  used  for  building, 
and  even  passes  into  a  compact  stone,  or  a  stone  of  which  the  separate 
parts  are  so  minute  as  not  to  be  distinguishable  from  each  other  by  the 
naked  eye. 

Many  limestones  are  made  up  entirely  of  minute  fragments  of  shells 
and  coral,  or  of  calcareous  sand  cemented  together.  These  last  might 
be  called  "  calcareous  sandstones  ;"  but  that  term  is  more  properly  ap- 
plied to  a  rock  in  which  the  grains  are  partly  calcareous  and  partly  sili- 
ceous, or  to  quartzose  sandstones,  having  a  cement  of  carbonate  of  lime. 

The  variety  of  limestone  called  "  oolite"  is  composed  of  numerous 
small  egg-like  grains,  resembling  the  roe  of  a  fish,  each  of  which  has 
usually  a  small  fragment  of  sand  as  a  nucleus,  around  which  concentric 
layers  of  calcareous  matter  have  accumulated. 

Any  limestone  which  is  sufficiently  hard  to  take  a  fine  polish  is  called 
marble.  Many  of  these  are  fossiliferous ;  but  statuary  marble,  which  is 
also  called  saccharine  limestone,  as  having  a  texture  resembling  that  of 
loaf-sugar,  is  devoid  of  fossils,  and  is  in  many  cases  a  member  of  the 
metamorphic  series. 

Siliceous  limestone  is  an  intimate  mixture  of  carbonate  of  lime  and 
flint,  and  is  harder  in  proportion  as  the  flinty  matter  predominates. 

The  presence  of  carbonate  of  lime  in  a  rock  may  be  ascertained  by 
applying  to  the  surface  a  small  drop  of  diluted  sulphuric,  nitric,  or  mu- 
riatic acids,  or  strong  vinegar ;  for  the  lime,  having  a  greater  chemical 
affinity  for  any  one  of  these  acids  than  for  the  carbonic,  unites  imme- 
diately with  them  to  form  new  compounds,  thereby  becoming  a  sulphate, 
nitrate,  or  muriate  of  lime.  The  carbonic  acid,  when  thus  liberated 
from  its  union  with  the  lime,  escapes  in  a  gaseous  form,  and  froths  up 
or  effervesces  as  it  makes  its  way  in  small  bubbles  through  the  drop  ot 
liquid.  This  effervescence  is  brisk  or  feeble  in  proportion  as  the  lime- 
stone is  pure  or  impure,  or,  in  other  words,  according  to  the  quantity  of 
foreign  matter  mixed  with  the  carbonate  of  lime.  Without  the  aid  ot 
this  test,  the  most  experienced  eye  cannot  always  detect  the  presence  ol 
carbonate  of  lime  in  rocks. 

The  above-mentioned  three  classes  of  rocks,  the  siliceous,  argillaceous, 
and  calcareous,  pass  continually  into  each  other,  and  rarely  occur  in  a 
perfectly  separate  and  pure  form.  Thus  it  is  an  exception  to  the  general 
rule  to  meet  with  a  limestone  as  pure  as  ordinary  white  chalk,  or  with 
clay  as  aluminous  as  that  used  in  Cornwall  for  porcelain,  or  with 
sand  so  entirely  composed  of  siliceous  grains  as  the  white  sand  of  Alum 
Bay  in  the  Isle  of  Wight,  or  sandstone  so  pure  as  the  grit  of  Fontaine- 


CH.  II.J  FOBMS   OF   STRATIFICATION.  13 

bleau,  used  for  pavement  in  France.  More  commonly  we  find  sand  and 
clay,  or  clay  and  marl,  intermixed  in  tne  same  mass.  When  the  sand 
and  clay  are  each  in  considerable  quantity,  the  mixture  is  called  loam. 
If  there  is  much  calcareous  matter  in  clay  it  is  called  marl ;  but  this 
term  has  unfortunately  been  used  so  vaguely,  as  often  to  be  very  ambig- 
uous. It  has  been  applied  to  substances  in  which  there  is  no  lime ;  as, 
to  that  red  loam  usually  called  red  marl  in  certain  parts  of  England. 
Agriculturists  were  in  the  habit  of  calling  any  soil  a  marl,  which,  like 
true  marl,  fell  to  pieces  readily  on  exposure  to  the  air.  Hence  arose  the 
confusion  of  using  this  name  for  soils  which,  consisting  of  loam,  were 
easily  worked  with  the  plough,  though  devoid  of  lime. 

Marl  slate  bears  the  same  relation  to  marl  which  shale  bears  to  clay, 
being  a  calcareous  shale.  It  is  very  abundant  in  some  countries,  as  in 
the  Swiss  Alps.  Argillaceous  or  marly  limestone  is  also  of  common  oc- 
currence. 

There  are  few  other  kinds  of  rock  which  enter  so  largely  into  the 
composition  of  sedimentary  strata  as  to  make  it  necessary  to  dwell  here 
on  their  characters.  I  may,  however,  mention  two  others, — magnesian 
limestone  or  dolomite,  and  gypsum.  Magnesian  limestone  is  composed 
of  carbonate  of  lime  and  carbonate  of  magnesia ;  the  proportion  of  the 
latter  amounting  in  some  cases  to  nearly  one-half.  It  effervesces  much 
more  slowly  and  feebly  with  acids  than  common  limestone.  In  England 
this  rock  is  generally  of  a  yellowish  color  ;  but  it  varies  greatly  in  min- 
eralogical  character,  passing  from  an  earthy  state  to  a  white  compact 
stone  of  great  hardness.  Dolomite,  so  common  in  many  parts  of  Ger- 
many and  France,  is  also  a  variety  of  magnesian  limestone,  usually  of  a 
granular  texture. 

G-ypsum. — Gypsum  is  a  rock  composed  of  sulphuric  acid,  lime,  and 
water.  It  is  usually  a  soft  whitish-yellow  rock,  with  a  texture  resembling 
that  of  loaf-sugar,  but  sometimes  it  is  entirely  composed  of  lenticular 
crystals.  It  is  insoluble  in  acids,  and  does  not  effervesce  like  chalk  and 
dolomite,  because  it  does  not  contain  carbonic  acid  gas,  or  fixed  air,  the 
lime  being  already  combined  with  sulphuric  acid,  for  which  it  has  a 
stronger  affinity  than  for  any  other.  Anhydrous  gvpsum  is  a  rare  vari- 
ety, into  which  water  does  not  enter  as  a  component  part.  Gypseous 
marl  is  a  mixture  of  gypsum  and  marl  Alabaster  is  a  granular  and 
compact  variety  of  gypsum  found  in  masses  large  enough  to  be  used  in 
sculpture  and  architecture.  It  is  sometimes  a  pure  snow-white  substance, 
as  that  of  Volterra  in  Tuscany,  well  known  as  being  carved  for  works  of 
art  in  Florence  and  Leghorn.  It  is  a  softer  stone  than  marble,  and  more 
easily  wrought 

Forms  of  stratification. — A  series  of  strata  sometimes  consists  of  one 
of  the  above  rocks,  sometimes  of  two  or  more  in  alternating  beds. 
Thus,  in  the  coal  districts  of  England,  for  example,  we  often  pass  through 
several  beds  of  sandstone,  some  of  finer,  others  of  coarser  grain,  some 
white,  others  of  a  dark  color,  and  below  these,  layers  of  shale  and  sand- 
stone or  beds  of  shale,  divisible  into  leaf-like  laminae,  and  containing 


14  ALTERNATIONS.  [Cfl.  II 

beautiful  impressions  of  plants.  Then  again  we  meet  with  beds  of  pure 
and  impure  coal,  alternating  with  shales  and  sandstones,  and  underneath 
the  whole,  perhaps,  are  calcareous  strata,  or  beds  of  limestone,  filled  with 
corals  and  marine  shells,  each  bed  distinguishable  from  another  by  cer- 
tain fossils,  or  by  the  abundance  of  particular  species  of  shells  or 
zoophytes. 

This  alternation  of  different  kinds  of  rock  produces  the  most  distinct 
stratification ;  and  we  often  find  beds  of  limestone  and  marl,  conglom- 
erate and  sandstone,  sand  and  clay,  recurring  again  and  again,  in  nearly 
regular  order,  throughout  a  series  of  many  hundred  strata.  The  causes 
which  may  produce  these  phenomena  are  various,  and  have  been  fully 
discussed  in  my  treatise  on  the  modern  changes  of  the  earth's  surface.* 
It  is  there  seen  that  rivers  flowing  into  lakes  and  seas  are  charged  with 
sediment,  varying  in  quantity,  composition,  color,  and  grain,  according  to 
the  seasons ;  the  waters  are  sometimes  flooded  and  rapid,  at  other  periods 
low  and  feeble ;  different  tributaries,  also,  draining  peculiar  countries  and 
soils,  and  therefore  charged  with  peculiar  sediment,  are  swollen  at  distinct 
periods.  It  was  also  shown  that  the  waves  of  the  sea  and  currents  un- 
dermine the  cliffs  during  wintry  storms,  and  sweep  away  the  materials 
into  the  deep,  after  which  a  season  of  tranquillity  succeeds,  when  nothing 
but  the  finest  mud  is  spread  by  the  movements  of  the  ocean  over  the 
same  submarine  area. 

It  is  not  the  object  of  tile  present  work  to  give  a  description  of  these 
operations,  repeated  as  they  are,  year  after  year,  and  century  after  century ; 
but  I  may  suggest  an  explanation  of  the  manner  in  which  some  micaceous 
sandstones  have  originated,  namely,  those  in  which  we  see  innumerable 
thin  layers  of  mica  dividing  layers  of  fine  quartzose  sand.  I  observed  the 
same  arrangement  of  materials  in  recent  mud  deposited  in  the  estuary  of 
La  Roche  St.  Bernard  in  Brittany,  at  the  mouth  of  the  Loire.  The  sur- 
rounding rocks  are  of  gneiss,  which,  by  its  waste,  supplies  the  mud :  when 
this  dries  at  low  water,  it  is  found  to  consist  of  brown  laminated  clay, 
divided  by  thin  seams  of  mica.  The  separation  of  the  mica  in  this  case,  or 
in  that  of  micaceous  sandstones,  may  be  thus  understood.  If  we  take  a 
handful  of  quartzose  sand,  mixed  with  mica,  and  throw  it  into  a  clear 
running  stream,  we  see  the  materials  immediately  sorted  by  the  water, 
the  grains  of  quartz  falling  almost  directly  to  the  bottom,  while  the  plates 
of  mica  take  a  much  longer  time  to  reach  the  bottom,  and  are  carried 
farther  down  the  stream.  At  the  first  instant  the  water  is  turbid,  but 
immediately  after  the  flat  surfaces  of  the  plates  of  mica  are  seen  all  alone 
reflecting  a  silvery  light,  as  they  descend  slowly,  to  form  a  distinct  mica- 
ceous lamina.  The  mica  is  the  heavier  mineral  of  the  two ;  but  it  re- 
mains a  longer  time  suspended  in  the  fluid,  owing  to  its  greater  extent  of 
surface.  It  is  easy,  therefore,  to  perceive  that  where  such  mud  is  acted 
upon  by  a  river  or  tidal  current,  the  thin  plates  of  mica  will  be  carried 

*  Consult  Index  to   Principles  of  Geology,    " Stratification,"   "Currents," 
•Deltas,"  "Water,"  &c. 


CH.  II]  HORIZONTALI'LT   OF   STRATA."  15 

farther,  and  not  deposited  in  the  same  places  as  the  grains  of  quartz;  and 
since  the  force  and  velocity  of  the  stream  varies  from  time  to  time,  layers 
of  mica  or  of  sand  will  be  thrown  down  successively  on  the  same  area. 

Original  horizontally. — It  is  said  generally  that  the  upper  and 
under  surfaces  of  strata,  or  the  planes  of  stratification,  are  parallel. 
Although  this  is  not  strictly  true,  they  make  an  approach  to  paral- 
lelism, for  the  same  reason  that  sediment  is  usually  deposited  at  first 
in  nearly  horizontal  layers.  The  reason  of  this  arrangement  can  by 
no  means  be  attributed  to  an  original  evenness  or  horizontally  in  the 
bed  of  the  sea ;  for  it  is  ascertained  that  in  those  places  where  no 
matter  has  been  recently  deposited,  the  bottom  of  the  ocean  is  often  as 
uneven  as  that  of  the  dry  land,  having  in  like  manner  its  hills,  valleys, 
and  ravines.  Yet  if  the  sea  should  sink,  or  the  water  be  removed  near 
the  mouth  of  a  large  river  where  a  delta  has  been  forming,  we  should 
see  extensive  plains  of  mud  and  sand  laid  dry,  which,  to  the  eye,  would 
appear  perfectly  level,  although,  in  reality,  they  would  slope  gently  from 
the  land  towards  the  sea. 

This  tendency  in  newly-formed  strata  to  assume  a  horizontal  position 
arises  principally  from  the  motion  of  the  water,  which  forces  along  par- 
ticles of  sand  or  mud  at  the  bottom,  and  causes  them  to  settle  in  hollows 
or  depressions,  where  they  are  less  exposed  to  the  force  of  a  current  than 
when  they  are  resting  on  elevated  points.  The  velocity  of  the  current 
and  the  motion  of  the  superficial  waves  diminish  from  the  surface 
downwards,  and  are  least  in  those  depressions  where  the  water  is 
deepest. 

A  good  illustration  of  the  principle  here  alluded  to  may  be  sometimes 
seen  in  the  neighborhood  of  a  volcano,  when  a  section,  whether  natural 
or  artificial,  has  laid  open  to  view  a  succession  of  various-colored  layers 
of  sand  and  ashes,  which  have  fallen  in  showers  upon  uneven  ground. 
Thus  let  A  B  (fig.  1)  be  two  ridges  with  an  intervening  valley.  These 
original  inequalities  of  the  surface  have  been  gradually  effaced  by  beds 
of  sand  and  ashes  c,  c?,  e,  the  surface  at  e  being  quite  level.  It  will  be 
seen  that  although  the  materials  of  the  first  layers  have  accommodated 

themselves  in  a  great  degree  to  the  shape 
of  the  ground  A  B,  yet  each  bed  is  thick- 
est at  the  bottom.  At  first  a  great  many 
particles  would  be  carried  by  their  own 
gravity  down  the  steep  sides  of  A  and  B, 
and  others  would  afterwards  be  blown  by  the  wind  as  they  fell  off*  the 
ridges,  and  would  settle  in  the  hollow,  which  would  thus  become  more 
and  more  effaced  as  the  strata  accumulated  from  c  to  e.  This  levelling 
operation  may  perhaps  be  rendered  more  clear  to  the  student  by  sup- 
posing a  number  of  parallel  trenches  to  be  dug  in  a  plain  of  moving 
sand,  like  the  African  desert,  in  which  case  the  wind  would  soon  cause 
all  signs  of  these  trenches  to  disappear,  and  the  surface  would  be  as 
uniform  as  before.  Now,  water  in  motion  can  exert  this  levelling  power 
on  similar  materials  more  easily  than  air,  for  almost  all  stones  lose  in 


16 


DIAGONAL   OR  CKOS6  STRATIFICATION. 


[On.  11. 


water  more  than  a  third  of  the  weight  which  they  have  in  air,  the  spe- 
cific gravity  of  rocks  being  in  general  as  2^  when  compared  to  that  of 
water,  which  is  estimated  at  1.  But  the  buoyancy  of  sand  or  mud 
would  be  still  greater  in  the  sea,  as  the  density  of  salt  water  exceeds 
that  of  fresh. 

Yet,  however  uniform  and  horizontal  may  be  the  surface  of  new  de- 
posits in  general,  there  are  still  many  disturbing  causes,  such  as  eddies 
in  the  water,  and  currents  moving  first  in  one  and  then  in  another 
direction,  which  frequently  cause  irregularities.  We  may  sometimes 
follow  a  bed  of  limestone,  shale,  or  sandstone,  for  a  distance  of  many 
hundred  yards  continuously ;  but  we  generally  find  at  length  that  each 
individual  stratum  thins  out,  and  allows  the  beds  which  were  previously 
above  and  below  it  to  meet.  If  the  materials  are  coarse,  as  in  grits  and 
conglomerates,  the  same  beds  can  rarely  be  traced  many  yards  without 
varying  in  size,  and  often  coming  to  an  end  abruptly.  (See  fig.  2.) 

Fig.  2. 


Section  of  strata  of  sandstone,  grit,  and  conglomerate. 

Diagonal  or  Cross  Stratification. — There  is  also  another  phenomenon 
of  frequent  occurrence.  We  find  a  series  of  larger  strata,  each  of  which 
is  composed  of  a  number  of  minor  layers  placed  obliquely  to  the  general 

Fig.  3. 


Section  of  sand  at  Sandy  Hill,  near  Biggleswade,  Bedfordshire. 
Height  20  feet.    (Green-sand  formation.) 

planes  of  stratification.  To  this  diagonal  arrangement  the  name  ol 
"false  or  cross  stratification"  has  been  given.  Thus  in  the  annexed  sec- 
tion (fig.  3)  we  see  seven  or  eight  large  beds  of  loose  sand,  yellow  and 


CH.  IL] 


CAUSES   OF   DIAGONAL   STRATIFICATION. 


17 


brown,  and  the  lines  a,  6,  c,  mark  some  of  the  principal  planes  of  strati- 
fication, which  are  nearly  horizontal:  But  the  greater  part  of  the  sub- 
ordinate laminae  do  not  conform  to  these  planes,  but  have  often  a  steep 
slope,  the  inclination  being  sometimes  towards  opposite  points  of  the 
compass.  When  the  sand  is  loose  and  incoherent,  as  in  the  case  here 
represented,  the  deviation  from  parallelism  of  the  slanting  laminae  can- 
not possibly  be  accounted  for  by  any  rearrangement  of  the  particles  ac- 
quired during  the  consolidation  of  the  rock.  In  what  manner  then  can 
such  irregularities  be  due  to  original  deposition  ?  We  must  suppose 
that  at  the  bottom  of  the  sea,  as  well  as  in  the  beds  of  rivers,  the  mo- 
tions of  waves,  currents,  and  eddies  often  cause  mud,  sand,  and  gravel 
to  be  thrown  down  in  heaps  on  particular  spots,  instead  of  being  spread 
out  uniformly  over  a  wide  area.  Sometimes,  when  banks  are  thus 
formed,  currents  may  cut  passages  through  them,  just  as  a  river  forms 
its  bed.  Suppose  the  bank  A  (fig.  4)  to  be  thus  formed  with  a  steep 


Fi«.4 


C  D 

sloping  side,  and  the  water  being  in  a  tranquil  state,  the  layer  of  sedi- 
ment No.  1  is  thrown  down  upon  it,  conforming  nearly  to  its  surface. 
Afterwards  the  other  layers,  2,  3,  4,  may  be  deposited  in  succession,  so 
that  the  bank  B  C  D  is  formed.  If  the  current  then  increases  in  ve- 
locity, it  may  cut  away  the  upper  portion  of  this  mass  down  to  the 
dotted  line  e  (fig.  4),  and  deposit  the  materials  thus  removed  farther  on, 
so  as  to  form  the  layers  5,  6,  7,  8.  We  have  now  the  bank  B  C  D  E 
(fig.  5),  of  which  the  surface  is  almost  level,  and  on  which  the  nearly 


Fig.  5. 


horizontal  layers,  9,  10,  11,  may  then  accumulate.  It  was  shown  in  fig. 
3  that  the  diagonal  layers  of  successive  strata  may  sometimes  have  an 
opposite  slope.  This  is  well  seen  in  some  cliffs  of  loose  sand  on  the 

Suffolk  coast.  A  portion  of  one  of 
these  is  represented  in  fig.  6,  where 
the  layers,  of  which  there  are  about 
six  in  the  thickness  of  an  inch,  are 
composed  of  quartzose  grains.  This 
arrangement  may  have  been  due  to 
the  altered  direction  of  the  tides  and 


Cliff  between  Mismer  and  Dnnwich.  currents  ill  the  same  place. 


18  CAUSES  OF  DIAGONAL  STRATIFICATION.  [Ca.  II 

The  description  above  given  of  the  slanting  position  of  the  minoi 
layers  constituting  a  single  stratum  is  in  certain  cases  applicable  on  a 
much  grander  scale  to  masses  several  hundred  feet  thick,  and  many  miles 
in  extent.  A  fine  example  may  be  seen  at  the  base  of  the  Maritime 
Alps  near  Nice.  The  mountains  here  terminate  abruptly  in  the  sea,  so 
that  a  depth  of  many  hundred  fathoms  is  often  found  within  a  stone's 
throw  of  the  beach,  and  sometimes  a  depth  of  3000  feet  within  half  a 
mile.  But  at  certain  points,  strata  of  sand,  marl,  or  conglomerate,  in- 
tervene between  the  shore  and  the  mountains,  as  in  the  annexed  fig.  (7), 
where  a  vast  succession  of  slanting  beds  of  gravel  and  sand  may  bo 

Monte  Calvo.  Fig.  T. 


Section  from  Monte  Calvo  to  tho  sea  by  the  valley  of  Magnan,  near  Nice. 
A.  Dolomite  and  sandstone.    (Green-sand  formation  ?) 
a,  &,  d.  Beds  of  gravel  and  sand. 
c.  Fine  marl  and  sand  of  St.  Madeleine,  with  marine  shells. 

traced  from  the  sea  to  Monte  Calvo,  a  distance  of  no  less  than  9  miles 
in  a  straight  line.  The  dip  of  these  beds  is  remarkably  uniform,  being 
always  southward  or  towards  the  Mediterranean,  at  an  angle  of  about 
25°.  They  are  exposed  to  view  in  nearly  vertical  precipices,  varying 
from  200  to  600  feet  in  height,  which  bound  the  valley  through  which 
the  river  Magnan  flows.  Although  in  a  general  view,  the  strata  appear 
to  be  parallel  and  uniform,  they  are  nevertheless  found,  when  examined 
closely,  to  be  wedge-shaped,  and  to  thin  out  when  followed  for  a  few 
hundred  feet  or  yards,  so  that  we  may  suppose  them  to  have  been 
thrown  down  originally  upon  the  side  of  a  steep  bank,  where  a  river  or 
alpine  torrent  discharged  itself  into  a  deep  and  tranquil  sea,  and  formed 
a  delta,  which  advanced  gradually  from  the  base  of  Monte  Calvo  to  a 
distance  of  9  miles  from  the  original  shore.  If  subsequently  this  part  of 
the  Alps  and  bed  of  the  sea  were  raised  700  feet,  the  coast  would  acquire 
its  present  configuration,  the  delta  would  emerge,  and  a  deep  channel 
might  then  be  cut  through  it  by  a  river. 

It  is  well  known  that  the  torrents  and  streams,  which  now  descend 
from  the  alpine  declivities  to  the  shore,  bring  down  annually,  when  the 
snow  melts,  vast  quantities  of  shingle  and  sand,  and  then,  as  they  sub- 
side, fine  mud,  while  in  summer  they  are  nearly  or  entirely  dry  ;  so  that 
it  may  be  safely  assumed,  that  deposits  like  those  of  the  valley  of  the 
Magnan,  consisting  of  coarse  gravel  alternating  with  fine  sediment,  are 
still  in  progress  at  many  points,  as,  for  instance,  at  the  mouth  of  the 
Var.  They  must  advance  upon  the  Mediterranean  in  the  form  of  great 
shoals  terminating  in  a  steep  talus  ;  such  being  the  original  mode  of  ac- 


Cn.  IL]  RIPPLE  MARK.  19 

cumulation  of  all  coarse  materials  conveyed  into  deep  water,  especially 
where  they  are  composed  in  great  part  of  pebbles,  which  cannot  be 
transported  to  indefinite  distances  by  currents  of  moderate  velocity.  By 
inattention  to  facts  and  inferences  of  this  kind,  a  very  exaggerated  esti- 
mate has  sometimes  been  made  of  the  supposed  depth  of  the  ancient 
ocean.  There  can  be  no  doubt,  for  example,  that  the  strata  a,  fig.  7, 
or  those  nearest  to  Monte  Calvo,  are  older  than  those  indicated  by  6,  and 
these  again  were  formed  before  c  ;  but  the  vertical  depth  of  gravel  and 
sand  in  any  one  place  cannot  be  proved  to  amount  even  to  1000  feet, 
although  it  may  perhaps  be  much  greater,  yet  probably  never  exceeding 
at  any  point  3000  or  4000  feet.  But  were  we  to  assume  that  all  the 
strata  were  once  horizontal,  and  that  their  present  dip  or  inclination  was 
due  to  subsequent  movements,  we  should  then  be  forced  to  conclude, 
that  a  sea  9  miles  deep  had  been  filled  up  with  alternate  layers  of  mud 
and  pebbles  thrown  down  one  upon  another. 

In  the  locality  now  under  consideration,  situated  a  few  miles  to  the 
west  of  Nice,  there  are  many  geological  data,  the  details  of  which  can- 
not be  given  in  this  place,  all  leading  to  the  opinion,  that  when  the 
deposit  of  the  Magnan  was  formed,  the  shape  and  outline  of  the  alpine 
declivities  and  the  shore  greatly  resembled  what  we  now  behold  at  many 
points  in  the  neighborhood.  That  the  beds,  a,  6,  c,  c?,  are  of  compara- 
tively modern  date  is  proved  by  this  fact,  that  in  seams  of  loamy  marl 
intervening  between  the  pebbly  beds  are  fossil  shells,  half  of  which  be- 
long to  species  now  living  in  the  Mediterranean. 

fiipple  mark. — The  ripple  mark,  so  common  on  the  surface  of  sand- 
stones of  all  ages  (see  fig.  8),  and  which  is  so  often  seen  on  the  sea-shore 

Fig.  8. 


Slab  of  ripple-marked  (new  red)  sandstone  from  Cheshire 


20  RIPPLE   MARE.  [Cii.  II 

at  low  tide,  seems  to  originate  in  the  drifting  of  materials  along  the 
bottom  of  the  water,  in  a  manner  very  similar  to  that  which  may  explain 
the  inclined  layers  above  described.  This  ripple  is  not  entirely  confined 
to  the  beach  between  high  and  low  water  mark,  but  is  also  produced  on 
sands  which  are  constantly  covered  by  water.  Similar  undulating  ridges 
and  furrows  may  also  be  sometimes  seen  on  the  surface  of  drift  snow  and 
blown  sand.  The  following  is  the  manner  in  which  I  once  observed  the 
motion  of  the  air  to  produce  this  effect  on  a  large  extent  of  level  beach, 
exposed  at  low  tide  near  Calais.  Clouds  of  fine  white  sand  were  blown 
from  the  neighboring  dunes,  so  as  to  cover  the  shore,  and  whiten  a  dark 
level  surface  of  sandy  mud,  and  this  fresh  covering  of  sand  was  beauti- 
fully rippled.  On  levelling  all  the  small  ridges  and  furrows  of  this  ripple 
over  an  area  of  several  yards  square,  I  saw  them  perfectly  restored  in 
about  ten  minutes,  the  general  direction  of  the  ridges  being  always  at 
right  angles  to  that  of  the  wind.  The  restoration  began  by  the  appear- 
ance here  and  there  of  small  detached  heaps  of  sand,  which  soon 
lengthened  and  joined  together,  so  as  to  form  long  sinuous  ridges  with 
intervening  furrows.  Each  ridge  had  one  side  slightly  inclined,  and  the 
other  steep  ;  the  lee-side  being  always  steep,  as  5,  ct — d,  e  ;  the  windward- 
side  a  gentle  slope,  as  a,  6, — c,  c?,  fig.  9.  When  a  gust  of  wind  blew 


Fig.  9. 


with  sufficient  force  to  drive  along  a  cloud  of  sand,  all  the  ridges  were 
seen  to  be  in 'motion  at  once,  each  encroaching  on  the  furrow  before  it, 
and,  in  the  course  of  a  few  minutes,  filling  the  place  which  the  furrows 
had  occupied.  The  mode  of  advance  was  by  the  continual  drifting  of 
grains  of  sand  up  the  slopes  a  b  and  c  d,  many  of  which  grains,  when 
they  arrived  at  b  and  d,  fell  over  the  scarps  b  c  and  d  e,  and  were  under 
shelter  from  the  wind ;  so  that  they  remained  stationary,  resting,  ac- 
cording to  their  shape  and  momentum,  on  different  parts  of  the  descent, 
and  a  few  only  rolling  to  the  bottom.  In  this  manner  each  ridge  was 
distinctly  seen  to  move  slowly  on  as  often  as  the  force  of  the  wind  aug- 
mented. Occasionally  part  of  a  ridge,  advancing  more  rapidly  than  the 
rest,  overtook  the  ridge  immediately  before  it,  and  became  confounded 
with  it,  thus  causing  those  bifurcations  and  branches  which  are  so  com 
mon,  and  two  of  which  are  seen  in  the  slab,  fig.  8.  We  may  observe 
this  configuration  in  sandstones  of  all  ages,  and  in  them  also,  as  now  on 
the  sea-coast,  we  may  often  detect  two  systems  of  ripples  interfering  with 
each  other ;  one  more  ancient  and  half-effaced,  and  a  newer  one,  in  which 
the  grooves  and  ridges  are  more  distinct,  and  in  a  different  direction. 
This  crossing  of  two  sets  of  ripples  arises  from  a  ehange  of  wind,  and  the 
new  direction  in  which  the  waves  are  thrown  on  the  shore. 

The  ripple  mark  is  usually  an  indication  of  a  sea-beach,  or  of  water 
from  6  to  10  feet  deep,  for  the  agitation  caused  by  waves  even  during 


CH.  IH]      GKADUAL  DEPOSITION  INDICATED  BY  FOSSILS.  21 

storms  extends  to  a  very  slight  depth.  To  this  rule,  however,  there  are 
some  exceptions,  and  recent  ripple-marks  have  been  observed  at  the  depth 
of  60  or  70  feet.  It  has  also  been  ascertained  that  currents  or  large 
bodies  of  water  in  motion  may  disturb  mud  and  sand  at  the  depth  of  300 
or  even  450  feet.*  Beach  ripple,  however,  may  usually  be  distinguished 
from  current  ripple  by  frequent  changes  in  its  direction.  In  a  slab  of 
sandstone,  not  more  than  an  inch  thick,  the  furrows  or  ridges  of  an  an- 
cient ripple  may  often  be  seen  in  several  successive  laminae  to  run  to- 
wards different  points  of  the  compass. 


CHAPTER  HI. 

ARRANGEMENT    OF   FOSSILS   IN    STRATA FRESHWATER   AND   MARINE. 

Successive  deposition  indicated  by  fossils— Limestones  formed  of  corals  and  shells 
— Proofs  of  gradual  increase  of  strata  derived  from  fossils — Serpula  attached 
to  spatangus — "Wood  bored  by  teredina — Tripoli  and  semi-opal  formed  of  in- 
fusoria— Chalk  derived  principally  from  organic  bodies — Distinction  of  fresh- 
water from  marine  formations — Genera  of  freshwater  and  land  shells — Rules 
for  recognizing  marine  testacea — Gyrogonite  and  chara — Freshwater  hshes — 
Alternation  of  marine  and  freshwater  deposits — Lym-Fiord. 

HAVING  in  the  last  chapter  considered  the  forms  of  stratification  so 
far  as  they  are  determined  by  the  arrangement  of  inorganic  matter,  we 
may  now  turn  our  attention  to  the  manner  in  which  organic  remains  are 
distributed  through  stratified  deposits.  We  should  often  be  unable  to 
detect  any  signs  of  stratification  or  of  successive  deposition,  if  particular 
kinds  of  fossils  did  not  occur  here  and  there  at  certain  depths  in  the 
mass.  At  one  level,  for  example,  univalve  shells  of  some  one  or  more 
species  predominate  ;  at  another,  bivalve  shells ;  and  at  a  third,  corals  ; 
while  in  some  formations  we  find  layers  of  vegetable  matter,  commonly 
derived  from  land  plants,  separating  strata. 

It  may  appear  inconceivable  to  a  beginner  how  mountains,  several 
thousand  feet  thick,  can  have  become  filled  with  fossils  from  top  to  bot- 
tom ;  but  the  difficulty  is  removed,  when  he  reflects  on  the  origin  of 
stratification,  as  explained  in  the  last  chapter,  and  allows  sufficient  time 
for  the  accumulation  of  sediment.  He  must  never  lose  sight  of  the  fact 
that,  during  the  process  of  deposition,  each  separate  layer  was  once  the 
uppermost,  and  covered  immediately  by  the  water  in  which  aquatic  ani- 
mals lived.  Each  stratum  in  fact,  however  far  it  may  now  lie  beneath  the 
surface,  was  once  in  the  state  of  shingle,  or  loose  sand  or  soft  mud  at  the 
bottom  of  the  sea,  in  which  shells  and  other  bodies  easily  became  enveloped. 

By  attending  to  the  nature  of  these  remains,  we  are  often  enabled  to 
determine  whether  the  deposition  was  slow  or  rapid,  whether  it  took 
place  in  a  deep  or  shallow  sea,  near  the  shore  or  far  from  land,  and 
whether  the  water  was  salt,  brackish,  or  fresh.  Some  limestones  consist 

e    Edin.  New  PhiL  Journ.  vol.  xxxi.;  and  Darwin,  Vole.  Islands,  p.  134. 


22 


GKADUAL   DEPOSITION 


[On.  III. 


almost  exclusively  of  corals,  and  in  many  cases  ii  is  evident  that  the  present 
position  of  each  fossil  zoophyte  has  been  determined  by  the  manner  in 
which  it  grew  originally.  The  axis  of  the  coral,  for  example,  if  its  nat- 
ural growth  is  erect,  still  remains  at  right  angles  to  the  plane  of  stratifi- 
cation. If  the  stratum  be  now  horizontal,  the  round  spherical  heads  of 
certain  species  continue  uppermost,  and  their  points  of  attachment  are 
directed  downwards.  This  arrangement  is  sometimes  repeated  through- 
out a  great  succession  of  strata.  From  what  we  know  of  the  growth  of 
similar  zoophytes  in  modern  reefs,  we  infer  that  the  rate  of  increase  was 
extremely  slow,  and  some  of  the  fossils  must  have  flourished  for  ages  like 
forest  trees  before  they  attained  so  large  a  size.  During  these  ages,  the 
water  remained  clear  and  transparent,  for  such  corals  cannot  live  in  tur- 
bid water. 

In  like  manner,  when  we  see  thousands  of  full-grown  shells  dispersed 
everywhere  throughout  a  long  series  of  strata,  we  cannot  doubt  that 
time  was  required  for  the  multiplication  of  successive  generations  ;  and 
the  evidence  of  slow  accumulation  is  rendered  more  striking  from  the 
proofs,  so  often  discovered,  of  fossil  bodies  having  lain  for  a  time  on  the 
floor  of  the  ocean  after  death  before  they  were  imbedded  in  sediment. 
Nothing,  for  example,  is  more  common  than  to  see  fossil  oysters  in  clay, 
with  serpulae,  or  barnacles  (acorn-shells),  or  corals,  and  other  creatures, 
attached  to  the  inside  of  the  valves,  so  that  the  mollusk  was  certainly  not 
buried  in  argillaceous  mud  the  moment  it  died.  There  must  have  been 
an  interval  during  which  it  was  still  surrounded  with  clear  water,  when 
the  creatures  whose  remains  now  adhere  to  it,  grew  from  an  embryo  to  a 
mature  state.  Attached  shells  which  are  merely  external,  like  some  of  the 
serpulae  (a)  in  the  annexed  figure  (fig.  10),  may  often  have  grown  upon 
Fi&  10.  an  oyster  or  other  shell  while  the  an- 

imal within  was  still  living;  but  if 
they  are  found  on  the  inside,  it  could 
only  happen  after  the  death  of  the 
inhabitant  of  the  shell  which  affords 
the  support.  Thus,  in  fig.  10,  it  will 
be  seen  that  two  serpulae  have  grown 
on  the  interior,  one  of  them  exactly 
on  the  place  where  the  adductor  mus- 
cle of  the  Gryphcea  (a  kind  of  oys- 
ter) was  fixed. 

Some  fossil  shells,  even  if  simply 
attached  to  the  outside  of  others,  bear 
full  testimony  to  the  conclusion  above 
alluded  to,  namely,  that  an  interval 
elapsed  between  the  death  of  the 
creature  to  whose  shell  they  adhere, 
and  the  burial  of  the  same  in  mud  or 
sand.  The  sea-urchins  or  Echini,  so 
abundant  in  white  chalk,  afford  a  good 


ro58" 


e  °ute"i8 


CH.  III.] 


INDICATED   BY  FOSSILS. 


23 


illustration.  It  is  well  known  that  these  animals,  when  living,  are  inva- 
riably covered  with  numerous  suckers,  or  gelatinous  tubes,  called  "  ambu- 
lacral,"  because  they  serve  as  organs  of  motion.  They  are  also  armed  with 
spines  supported  by  rows  of  tubercles.  These  last  are  only  seen  after  the 
death  of  the  sea-urchin,  when  the  spines  have  dropped  off.  In  fig.  12  a 
living  species  of  Spatangus,  common  on  our  coast,  is  represented  with 


Fig.  11. 


Serpula  attached  to 

a  fossil  Spatangus 

from  the  chalk. 


Recent  Spatangus  with  the  spines 
removed  from  one  side. 

6.  Spine  and  tubercles,  nat  size, 
a.  The  same  magnified. 


one-half  of  its  shell  stripped  of  the  spines.  In  fig.  1 1  a  fossil  of  the 
same  genus  from  the  white  chalk  of  England  shows  the  naked  surface 
which  the  individuals  of  this  family  exhibit  when  denuded  of  their  bris- 
tles. The  full-grown  Serpula,  therefore,  which  now  adheres  externally, 
could  not  have  begun  to  grow  till  the  Spatangus  had  died,  and  the 
spines  were  detached. 

Now  the  series  of  events  here  attested  by  a  single  fossil  may  be  carried 
a  step  farther.  Thus,  for  example,  we  often  meet  with  a  sea-urchin  in 
the  chalk  (see  fig.  13),  which  has  fixed  to  it  the  lower  valve  of  a  Crania, 
Fig.  is.  a  genus  of  bivalve  mpllusca.  The  upper  valve  (6,  fig. 

13)  is  almost  invariably  wanting,  though  occasionally 
found  in  a  perfect  state  of  preservation  in  white  chalk 
at  some  distance.    In  this  case,  we  see  clearly  that  the 
sea-urchin  first  lived  from  youth  to  age,  then  died  and 
lost  its  spines,  which  were  carried  away.     Then  the 
a.  Echinus  from  the  young  Crania  adhered  to  the  bared  shell,  grew  and 
vafve'ofthe  Crania  P^hed  in  its  turn ;  after  which  the  upper  valve  was 
attached.  separated  from  the  lower  before  the  ^Echinus  became 

Z>.  Upper  valve  of  tba        * 

Crania  detached,      enveloped  in  chalky  mud. 

It  may  be  well  to  mention  one  more  illustration  of  the  manner  in 
which  single  fossils  may  sometimes  throw  light  on  a  former  state  of 
things,  both  in  the  bed  of  the  ocean  and  on  some  adjoining  land.  We 
meet  with  many  fragments  of  wood  bored  by  ship-worms,  at  various 
depths  in  the  clay  on  which  London  is  built.  Entire  branches  and  stems 
of  trees,  several  feet  in  length,  are  sometimes  dug  out,  drilled  all  over  by 
the  holes  of  these  borers,  the  tubes  and  shells  of  the  mollusk  still  re- 
maining in  the  cylindrical  hollows.  In  fig.  15  e,  a  representation  is 
given  of  a  piece  of  recent  wood  pierced  by  the  Teredo  navalis,  or  com- 
mon ship-worm,  which  destroys  wooden  piles  and  ships.  When  the 
cylindrical  tube  d  has  been  extracted  from  the  wood,  a  shell  is  seen  at 
the  larger  extremity,  composed  of  two  pieces,  as  shown  at  c.  In  like 


SLOW   DEPOSITION   OF   STEATA. 


[On.  IIL 


manner,  a  piece  of  fossil  wood  (a,  fig.  14)  has  been  perforated  by  an 
animal  of  a  kindred  but  extinct  genus,  called  Teredina  by  Lamarck. 
The  calcareous  tube  of  this  mollusk  was  united  and  as  it  were  soldered 


Fig.  14. 


Fig.  15. 


Fossil  and  recent  wood  drilled  by  perforating  Mollusca. 
Fig.  14.  a.  Fossil  wood  from  London  clay,  bored  by  Teredina. 

&.  Shell  and  tube  of  Teredina  per  sonata,  the  right-hand  figure  the  ventral,  the  left  the 

dorsal  view. 
Fig.  15.  e.  Eecent  wood  bored  by  Teredo. 

d.  Shell  and  tube  of  Teredo  navalis,  from  the  same. 

c.  Anterior  and  posterior  view  of  the  valves  of  same  detached  from  the  tube. 

on  to  the  valves  of  the  shell  (6),  which  therefore  cannot  be  detached 
from  the  tube,  like  the  valves  of  the  recent  Teredo.  The  wood  in  this 
fossil  specimen  is  now  converted  into  a  stony  mass,  a  mixture  of  clay 
and  lime  ;  but  it  must  once  have  been  buoyant  and  floating  in  the  sea, 
when  the  Teredince  lived  upon  it,  perforating  it  in  all  directions.  Again, 
before  the  infant  colony  settled  upon  the  drift-wood,  the  branch  of  a  tree 
must  have  been  floated  down  to  the  sea  by  a  river,  uprooted,  perhaps,  by 
a  flood,  or  torn  off  and  cast  into  the  waves  by  the  wind  :  and  thus  our 
thoughts  are  carried  back  to  a  prior  period,  when  the  tree  grew  for  years 
on  dry  l-md,  enjoying  a  fit  soil  and  climate. 

I  It  has  been  already  remarked  that  there  are  rocks  in  the  interior  of 
continents,  at  various  depths  in  the  earth,  and  at  great  heights  above  the 
sea,  almost  entirely  made  up  of  the  remains  of  zoophytes  and  testacea. 
Such  masses  may  be  compared  to  modern  oyster-beds  and  coral  reefs ; 
and,  like  them,  the  rate  of  increase  must  have  been  extremely  gradual. 
But  there  are  a  variety  of  stony  deposits  in  the  earth's  crust,  now  proved 
to  have  been  derived  from  plants  and  animals,  of  which  the  organic  ori- 
gin was  not  suspected  until  of  late  years,  even  by  naturalists.  Great 
surprise  was  therefore  created  by  the  recent  discovery  of  Professor  Ehren- 
berg  of  Berlin,  that  a  certain  kind  of  siliceous  stone,  called  tripoli,  was 
entirely  composed  of  millions  of  the  remains  of  organic  beings,  which 
the  Prussian  naturalist  refers  to  microscopic  Infusoria,  but  which  most 
others  now  believe  to  be  plants.  They  abound  in  freshwater  lakes  and 
ponds  in  England  and  other  countries,  and  are  termed  Diatomacea3  by 
those  naturalists  who  believe  in  their  vegetable  origin.  The  substance 


CH.  Ill] 


INFUSORIA  OF   TRIPOLI. 


25 


alluded  to  has  long  been  well  known  in  the  arts,  being  used  in  the  form 
of  powder  for  polishing  stones  and  metals.  It  has  been  procured,  among 
other  places,  from  Bilin,  in  Bohemia,  where  a  single  stratum,  extending 
over  a  wide  area,  is  no  less  than  14  feet  thick.  This  stone,  when  exam- 
ined with  a  powerful  microscope,  is  found  to  consist  of  the  siliceous 
plates  or  frustules  of  the  above-mentioned  Diatomacese,  united  together 


Fig.  16. 


Fig.  17. 


Fig.  IS. 


Fig.  20. 


Fig.  19. 


D 


EanUaria.  GaUonetta  GaUoneUa 

vulgaris  ?  distant,  ferruginea. 

These  figures  are  magnified  nearly  800  times,  except  the  lower  fignre  of  G.  ferruginea  (fig.  13  a), 
which  is  magnified  2000  times. 

without  any  visible  cement.  It  is  difficult  to  convey  an  idea  of  their 
extreme  minuteness ;  but  Ehrenberg  estimates  that  in  the  Bilin  tripoli 
there  are  41,000  millions  of  individuals  of  the  Ofaillonella  distant  (see 
fig.  17)  in  every  cubic  inch,  which  weighs  about  220  grains,  or  about 
187  millions  in  a  single  grain.  At  every  stroke,  therefore,  that  we  make 
with  this  polishing  powder,  several  millions,  perhaps  tens  of  millions,  of 
perfect  fossils  are  crushed  to  atoms. 

The  remains  of  these  Diatomacese  are  of  pure  silex,  and  their  forms 
are  various,  but  very  marked  and  constant  in  particular  genera  and  spe- 
cies. Thus,  in  the  family  Ba- 
cillaria  (see  fig.  16),  the  fos- 
sils preserved  in  tripoli  are 
seen  to  exhibit  the  same  di- 
visions and  transverse  lines 
which  characterize  the  living 
species  of  kindred  form.  With 
these,  also,  the  siliceous  splen- 
ic or  internal  supports  of  the 
freshwater  sponge,  or  Spon- 
gilla  of  Lamarck,  are  some- 
times intermingled  (see  the 
needle-shaped  bodies  in  fig. 
20).  These  flinty  cases  and 
spiculce,  although  hard,  are 
very  fragile,  breaking  like 
glass,  and  are  therefore  admi- 
rably adapted,  when  rubbed, 
for  wearing  down  into  a  fine 
powder  fit  for  polishing  the 
surface  of  metals. 

Fragment  of  semi-opal  from  the  great  bed  of  tripoli,  Bilin.         Besides  the  tripoli,  formed 
r!|  X    Th?™™  masmfied.  showing  circnl.r  articula-    exclusively  of  the  fossils  above 

ies  °f  GaUondla^  and  spicula5  described,  there  occurs  in  the 


26  FOSSIL  INFUSOKIA.  [On.  Ill 

upper  part  of  the  great  stratum  at  Bilin  another  heavier  and  more  compact 
stone,  a  kind  of  semi-opal,  in  which  innumerable  parts  of  Diatomacece 
and  spiculse  of  the  Spongilla  are  filled  with,  and  cemented  together  by. 
siliceous  matter.  It  is  supposed  that  the  siliceous  remains  of  the  most 
delicate  Diatomacese  have  been  dissolved  by  water,  and  have  thus  given 
rise  to  this  opal  in  which  the  more  durable  fossils  are  preserved  like  in- 
sects in  amber.  This  opinion  is  confirmed  by  the  fact  that  the  organic 
bodies  decrease  in  number  and  sharpness  of  outline  in  proportion  as  the 
opaline  cement  increases  in  quantity. 

In  the  Bohemian  tripoli  above  described,  as  in  that  of  Planitz  in  Sax- 
ony, the  species  of  DiatomaceaB  (or  Infusoria,  as  termed  by  Ehrenberg) 
are  freshwater ;  but  in  other  countries,  as  in  the  tripoli  of  the  Isle  of 
France,  they  are  of  marine  species,  and  they  all  belong  to  formations  of 
the  tertiary  period,  which  will  be  spoken  of  hereafter. 

A  well-known  substance,  called  bog-iron  ore,  often  met  with  in  peat- 
mosses, has  also  been  shown  by  Ehrenberg  to  consist  of  innumerable  ar- 
ticulated threads,  of  a  yellow  ochre  color,  composed  partly  of  flint  and 
partly  of  oxide  of  iron.  These  threads  are  the  cases  of  a  minute  micro- 
scopic body,  called  Gaillonella  ferruginea  (fig.  18). 

It  is  clear  that  much  time  must  have  been  required  for  the  accumulation 
of  strata  to  which  countless  generations  of  Diatomacea3  have  contributed 
their  remains ;  and  these  discoveries  lead  us  naturally  to  suspect  that  other 
deposits,  of  which  the  materials  have  usually  been  supposed  to  be  inorganic, 
may  in  reality  have  been  derived  from  microscopic  organic  bodies.  That 
this  is  the  case  with  the  white  chalk,  has  often  been  imagined,  this  rock 
having  been  observed  to  abound  in  a  variety  of  marine  fossils,  such  as 
echini,  testacea,  bryozoa,  corals,  sponges,  Crustacea,  and  fishes.  Mr.  Lons- 
dale,  on  examining,  Oct.,  1835,  in  the  museum  of  the  Geological  Society 
of  London,  portions  of  white  chalk  from  different  parts  of  England,  found, 
on  carefully  pulverizing  them  in  water,  that  what  appear  to  the  eye  simply 
as  white  grains  were,  in  fact,  well  preserved  fossils.  He  obtained  above 
a  thousand  of  these  from  each  pound  weight  of  chalk,  some  being  frag- 
ments of  minute  bryozoa  and  corallines,  others  entire  Foraminifera  and 
Cytheridae.  The  annexed  drawings  will  give  an  idea  of  the  beautiful 
forms  of  many  of  these  bodies.  The  figures  a  a  represent  their  natural 
size,  but,  minute  as  they  seem,  the  smallest  of  them,  such  as  a,  fig.  24, 

Cytheridm  and  Foraminifera  from  the  chalk. 
Fig.  21.  Fig.  22.  Fig.  23.  Fig.  24. 

u 


Cythere,  Mull.  Portion  of  Cristellaria  Rosalina. 

Cytherina,  Lam.      Nodosaria,  rotulata. 

are  gigantic  in  comparison  with  the  cases  of  Diatomacere  before  men- 
tioned. It  has,  moreover,  been  lately  discovered  that  the  chambers  into 
which  these  Foraminifera  are  divided  are  actually  often  filled  with  thou- 


CH.  in.]  FRESHWATER  AND  MARINE  FOSSILS.  27 

sands  of  well-preserved  organic  bodies,  which  abound  in  every  minute 
grain  of  chalk,  and  are  especially  apparent  in  the  white  coaling  of 
flints,  often  accompanied  by  innumerable  needle-shaped  spiculae  of 
sponges.  After  reflecting  on  these  discoveries,  we  are  naturally  led  on 
to  conjecture  that,  as  the  formless  cement  in  the  semi-opal  of  Bilin 
has  been  derived  from  the  decomposition  of  animal  and  vegetable  re- 
mains, so  also  many  chalk  flints  in  which  no  organic  structure  can  be 
recognized  may  nevertheless  have  constituted  a  part  of  microscopic 
animalcules. 

"  The  dust  we  tread  upon  was  once  alive  !" — BYBON. 

How  faint  an  idea  does  this  exclamation  of  the  poet  convey  of  the 
real  wonders  of  nature  !  for  here  we  discover  proofe  that  the  calcareous 
and  siliceous  dust  of  which  hills  are  composed  has  not  only  been  once 
alive,  but  almost  every  particle,  albeit  invisible  to  the  naked  eye,  still 
retains  the  organic  structure  which,  at  periods  of  time  incalculably  re- 
mote, was  impressed  upon  it  by  the  powers  of  life. 
,  Freshwater  and  marine  fossils. — Strata,  whether  deposited  in  salt 
or  fresh  water,  have  the  same  forms ;  but  the  imbedded  fossils  are 
very  different  in  the  two  cases,  because  the  aquatic  animals  which  fre- 
quent lakes  and  rivers  are  distinct  from  those  inhabiting  the  sea.  In 
the  northern  part  of  the  Isle  of  Wight  formations  of  marl  and  lime- 
stone, more  than  50  feet  thick,  occur,  in  which  the  shells  are  prin- 
cipally, if  not  all,  of  extinct  species.  Yet  we  recognize  their  freshwater 
origin,  because  they  are  of  the  same  genera  as  those  now  abounding 
in  ponds  and  lakes,  either  in  our  own  country  or  in  warmer  latitudes. 

In  many  parts  of  France,  as  in  Auvergne,  for  example,  strata  of  lime- 
stone, marl,  and  sandstone  are  found,  hundreds  of  feet  thick,  which  con- 
tain exclusively  freshwater  and  land  shells,  together  with  the  remains  of 
terrestrial  quadrupeds.  The  number  of  land  shells  scattered  through 
some  of  these  freshwater  deposits  is  exceedingly  great ;  and  there  are 
districts  in  Germany  where  the  rocks  scarcely  contain  any  other  fossils 
except  snail-shells  (helices)  ;  as,  for  instance,  the  limestone  on  the  left 
bank  of  the  Rhine,  between  Mayence  and  Worms,  at  Oppenheim,  Find- 
heim,  Budenheim,  and  other  places.  In  order  to  account  for  this  phe- 
nomenon, the  geologist  has  only  to  examine  the  small  deltas  of  torrents 
which  enter  the  Swiss  lakes  when  the  waters  are  low,  such  as  the  newly- 
formed  plain  where  the  Kander  enters  the  Lake  of  Thun.  He  there  sees 
sand  and  mud  strewed  over  with  innumerable  dead  land  shells,  which 
have  been  brought  down  from  valleys  in  the  Alps  in  the  preceding  spring, 
during  the  melting  of  the  snows.  Again,  if  we  search  the  sands  on  the 
borders  of  the  Rhine,  in  the  lower  part  of  its  course,  we  find  countless 
land  shells  mixed  with  others  of  species  belonging  to  lakes,  stagnant 
pools,  and  marshes.  These  individuals  have  been  washed  away  from 
the  alluvial  plains  of  the  great  river  and  its  tributaries,  some  from 
mountainous  regions,  others  from  the  low  country. 


28 


DISTINCTION  OF  FRESHWATER 


[On.  TIL 


Although  freshwater  formations  are  often  of  great  thickness,  yet  they 
are  usually  very  limited  in  area  when  compared  to  marine  deposits, 
just  as  lakes  and  estuaries  are  of  small  dimensions  in  comparison  with 
seas. 

We  may  distinguish  a  freshwater  formation,  first,  by  the  absence  of 
many  fossils  almost  invariably  met  with  in  marine  strata.  For  example, 
there  are  no  sea-urchins,  no  corals,  and  scarcely  any  zoophytes ;  no 
chambered  shells,  such  as  the  nautilus,  nor  microscopic  Foraminifera. 
But  it  is  chiefly  by  attending  to  the  forms  of  the  rnollusca  that  we  are 
guided  in  determining  the  point  in  question.  In  a  freshwater  deposit, 
the  number  of  individual  shells  is  often  as  great,  if  not  greater,  than  in 
a  marine  stratum  ;  but  there  is  a  smaller  variety  of  species  and  genera. 
This  might  be  anticipated  from  the  fact  that  the  genera  and  species  of 
recent  freshwater  and  land  shells  are  few  when  contrasted  with  the  ma- 
rine. Thus,  the  genera  of  true  mollusca  according  to  Blainville's  system, 
excluding  those  of  extinct  species  and  those  without  shells,  amount  to 
about  200  in  number,  of  which  the  terrestrial  and  freshwater  genera 
scarcely  form  more  than  a  sixth.* 

Almost  all  bivalve  shells,  or  those  of  acephalous  mollusca,  are  marine, 


Fig.  25. 


Fig.  26. 


Cyclas  obotata  ;  fossil.    Ilanta, 


Cyrena  consobrina  ;  fossil.    Grays,  Essex 


about  ten  only  out  of  ninety  genera  being  freshwater.     Among  these 
last,  the  four  most  common  forms,  both  recent  and  fossil,  are  Cyclas,  Cy- 


Fig.  27. 


Fig.  28. 


Fig.  29. 


Anodonta  Cordierii  ; 
fossil.    Paris. 


Anodonta  latimarginatzis  ; 
recent    Bahia. 


Unio  littoralis  ; 
recent    Auvergne. 


rena,  Unio,  and  Anodonta  (see  figures) ;  the  two  first  and  two  last  of 
which  are  so  nearly  allied  as  to  pass  into  each  other. 


See  Synoptic  Table  in  Blainville's  Malacologie. 


CH.  IIL] 


FROM  MARIXE  FORMATIONS. 


29 


Fig-  so. 


Gryphcea  incurva,  Sow.  (G. 

arcuata,  Lam.)  upper 

valve.    Lias. 

ludina.   (See  figures.) 

Fig.  81. 


Lamarck  divided  the  bivalve  mollusca  into  the 
Dimyary,  or  those  having  two  large  muscular 
impressions  in  each  valve,  as  a  b  in  the  Cyclas, 
fig.  25,  and  the  Monomyary,  such  as  the  oyster 
and  scallop,  in  which  there  is  only  one  of  these 
impressions,  as  is  seen  in  fig.  30.  Now,  as  none 
of  these  last,  or  the  unimuscular  bivalves,  are 
freshwater,  we  may  at  once  presume  a  deposit  in 
which  we  find  any  of  them  to  be  marine. 

The  univalve  shells  most  characteristic  of  fresh- 
water deposits  are,  Planorbis,  Lymnea,  and  Pa- 
But  to  these  are  occasionally  added  Physa,  Sue- 

Fig.  32.  Fig.  33. 


Planorbis  euompTialus  ; 
fossil    Isle  of  Wight 


Lymnea  longiscata ; 
fossil    Hants. 


Paludina  lento,  ; 
fossil    Hants. 


cinea,  Ancylus,  Valvata,  Melanopsis,  Melania,  and  Neritina.  (See  figures.) 

Fig.  34.  Fig.  85.  Fig.  36.  Fig.  37. 


Succinea  amphibia  ; 
fossil.    Loess,  Ehine. 


Ancylus  elegant  ; 
fossil    Hants. 


Valvata; 

fossil. 
Grays,  Essex. 


Physa  hypnorum  ; 
recent 


In  regard  to  one  of  these,  the  Ancylus  (fig.  35),  Mr.  Gray  observes 
that  it  sometimes  differs  in  no  respect  from  the  marine  Siphonaria,  ex- 
Fig.  83  Fig.  39.  Fig.  40.  Fig.  41. 


Auricula  ; 
recent    Ava. 


Melania, 
inquinata. 
Paris  basin. 


Melanopsis  "buc- 
cinoidea;  recent 
Asia. 


cept  in  the  animal.     The  shell,  however,  of  the  Ancylus  is  usually 
thinner.* 

*  Gray,  Phil.  Trans.  1835,  p.  302. 


so 


DISTINCTION   OF   FEESHWATEE 


[Ce.  III. 


Some  naturalists  include  Neritina  (fig.  42)  and  the  marine  Nerita 
(fig.  43)  in  the  same  genus,  it  being  scarcely  possible  to  distinguish  the 


Fig.  42. 


Fig.  43. 


Fig.  44. 


Neritina  globulus.    Paris  basin. 


Nerita  granulosa,    Paris  basin. 


two  by  good  generic  characters.  But,  as  a  general  rule,  the 
fluviatile  species  are  smaller,  smoother,  and  more  globular 
than  the  marine  ;  and  they  have  never,  like  the  JVeritce,  the 
inner  margin  of  the  outer  lip  toothed  or  crenulated.  (See 
fig.  43.) 

A  few  genera,  among  which  Cerithium  (fig.  44)  is  the  most 
abundant,  are  common  both  to  rivers  and  the  sea,  having  spe-    Cerituum 
cies  peculiar  to  each.   Other  genera,  like  Auricula  (fig.  38),  are    p^ris3  basin 
amphibious,  frequenting  marshes,  especially  near  the  sea. 

The  terrestrial  shells  are  all  univalves.  The  most  abundant  genera 
among  these,  both  in  a  recent  and  fossil  state,  are  Helix  (fig.  45),  Cy- 
dostoma  (fig.  46),  Pupa  (fig.  47),  Clausilia  (fig.  48),  Bulimus  (fig.  49), 


Fig.  46. 


Fig.  46. 


Helve,  Turonensis. 
Faluns,  Touraine. 


Cyclostoma 
elegam. 


Fig.  47.        Fig.  43.  Fig.  49. 


Pupa 
tridens. 
Loess. 


Clausilia 
bidens. 
Loess. 


Bulimus  lubricus. 
Loess,  Khine. 


and  Achatina  ;  which  two  last  are  nearly  allied  and  pass  into  each  other. 
The  Ampullaria  (fig.  50)  is  another  genus  of  shells,  inhabiting  rivers 
and  ponds  in  hot  countries.  Many  fossil  species  have 
been  referred  to  this  genus,  but  they  have  been  found 
chiefly  in  marine  formations,  and  are  suspected  by 
some  oonchologists  to  belong  to  Natica  and  other  ma- 
rine genera. 

All  univalve  shells  of  land  and  freshwater  species, 
with  the  exception  of  Melanopsis  (fig.  41),  and  Acha- 


Amputtaria  glauca, 
from  the  Jumna. 


Una,   which   has    a    slight   indentation,   have    entire 


mouths ;  and  this  circumstance  may  often  serve  as 
a  convenient  rule  for  distinguishing  freshwater  from  marine  strata ; 
since,  if  any  univalves  occur  of  which  the  mouths  are  not  entire,  we 
may  presume  that  the  formation  is  marine.  The  aperture  is  said  to  be 
entire  in  such  shells  as  the  Ampullaria  and  the  land  shells  (figs.  45 — 
49),  when  its  outline  is  not  interrupted  by  an  indentation  or  notch, 


OH.  Ill]  FROM   MARINE   FORMATIONS.  31 

such  as  that  seen  at  b  in  Ancillaria  (fig.  52) ;  or  is  not  prolonged  into 
a  canal,  as  that  seen  at  a  in  Pleurotoma  (fig.  51). 

The  mouths  of  a  large  proportion  of  the  marine  univalves  have  these 
notches  or  canals,  and  almost  all  such  species  are  carnivorous ;  whereas 

Fig.  51. 


Pleurotoma 

rotata. 

Subap.  hills, 

Italy. 


Ancillaria  subitlata.     Barton  clay. 

nearly  all  testacea  having  entire  mouths,  are  plant-eaters  ;  whether  the 
species  be  marine,  freshwater,  or  terrestrial. 

There  is,  however,  one  genus  which  affords  an  occasional  exception  to 
one  of  the  above  rules.  The  Cerithium  (fig.  44),  although  provided  with 
a  short  canal,  comprises  some  species  which  inhabit  salt,  others  brackish, 
and  others  fresh  water,  and  they  are  said  to  be  all  plant-eaters. 

Among  the  fossils  very  common  in  freshwater  deposits  are  the  shells 
of  Cypris,  a  minute  crustaceous  animal,  having  a  shell  much  resembling 
that  of  the  bivalve  mollusca.*  Many  minute  living  species  of  this  genus 
swarm  in  lakes  and  stagnant  pools  in  Great  Britain  ;  but  their  shells  are 
not,  if  considered  separately,  conclusive  as  to  the  freshwater  origin  of  a 
deposit,  because  the  majority  of  species  in  another  kindred  genus  of  the 
same  order,  the  Cytherina  of  Lamarck  (see  above,  fig.  21,  p.  26),  in- 
habit salt  water ;  and,  although  the  animal  differs  slightly,  the  shell  is 
scarcely  distinguishable  from  that  of  the  Cypris. 

The  seed-vessels  and  stems  of  Cham,  a  genus  of  aquatic  plants,  are 
very  frequent  in  freshwater  strata.  These  seed-vessels  were  called,  before 
their  true  nature  was  known,  gyrogonites,  and  were  supposed  to  be 
foraminiferous  shells.  (See  fig.  53  a.) 

The  Clutrce  inhabit  the  bottom  of  lakes  and  ponds,  and  flourish 
mostly  where  the  water  is  charged  with  carbonate  of  lime.  Their  seed- 
vessels  are  covered  with  a  very  tough  integument,  capable  of  resisting 
decomposition ;  to  which  circumstance  we  may  attribute  their  abundance 
in  a  fossil  state.  The  annexed  figure  (fig.  54)  represents  a  branch  of 
one  of  many  new  species  found  by  Professor  Amici  in  the  lakes  of 
northern  Italy.  The  seed-vessel  in  this  plant  is  more  globular  than  in 
the  British  Charce,  and  therefore  more  nearly  resembles  in  form  the  ex- 
tinct fossil  species  found  in  England,  France,  and  other  countries.  Tho 

*  For  figures  of  fossil  species  of  Purbeck,  see  below,  ch.  JOE. 


32 


FEESH WATER  AND  MARINE  FORMATIONS.  [OH.  III. 


stems,  as  well  as  the  seed-vessels,  of  these  plants  occur  both  in  modern 
shell  marl  and  in  ancient  freshwater  formations.     They  are  generally 


Fig.  53. 


Fig.  54. 


Ohara  medieaginula  ; 
fossil.    Upper  Eocene, 
Isle  of  Wight. 
a.  Seed-vessel, 

magnified  20 

diameters. 
&.  Stem,  magnified. 


Chara  elasUca  ;  recent    Italy. 


a.  Sessile  seed-vessel  between  the  divisions  of 
the  leaves  of  the  female  plant. 

&.  Magnified  transverse  section  of  a  branch, 
with  five  seed-vessels,  seen  from  below 
upwards. 


composed  of  a  large  tube  surrounded  by  smaller  tubes  ;  the  whole  stem 
being  divided  at  certain  intervals  by  transverse  partitions  or  joints. 
(See  6,  fig.  53.) 

It  is  not  uncommon  to  meet  with  layers  of  vegetable  matter,  impres- 
sions of  leaves,  and  branches  of  trees,  in  strata  containing  freshwater 
shells  ;  and  we  also  find  occasionally  the  teeth  and  bones  of  land  quad- 
rupeds, of  species  now  unknown.  The  manner  in  which  such  remains 
are  occasionally  carried  by  rivers  into  lakes,  especially  during  floods,  has 
been  fully  treated  of  in  the  "  Principles  of  Geology."* 

The  remains  of  fish  are  occasionally  useful  in  determining  the  fresh- 
water origin  of  strata.  Certain  genera,  such  as  carp,  perch,  pike,  and 
loach  ( Cyprinus,  Perca,  JEsoz,  and  Cobitis),  as  also  LeUas,  being  pe- 
culiar to  freshwater.  Other  genera  contain  some  freshwater  and  some 
marine  species,  as  Cottus,  Mugil,  and  Anguilla,  or  eel.  The  rest  are 
either  common  to  rivers  and  the  sea,  as  the  salmon  ;  or  are  exclusively 
characteristic  of  salt  water.  The  above  observations  respecting  fossil 
fishes  are  applicable  only  to  the  more  modern  or  tertiary  deposits  ;  for 
in  the  more  ancient  rocks  the  forms  depart  so  widely  from  those  of  ex- 
isting fishes,  that  it  is  very  difficult,  at  least  in  the  present  state  of  sci- 
ence, to  derive  any  positive  information  from  icthyolites  respecting  the 
element  in  which  strata  were  deposited. 

-j-  The  alternation  of  marine  and  freshwater  formations,  both  on  a  small 
and  large  scale,  are  facts  well  ascertained  in  geology.  When  it  occurs 
on  a  small  scale,  it  may  have  arisen  from  the  alternate  occupation  of 
certain  spaces  by  river  water  and  the  sea ;  for  in  the  flood  season  the 
river  forces  back  the  ocean  and  freshens  it  over  a  large  area,  depositing 
at  the  same  time  its  sediment ;  after  which  the  salt  water  again  returns, 
and,  on  resuming  its  former  place,  brings  with  it  sand,  mud,  and  marine 
•helk 

*  See  Index  of  Principles,  "  Fossilization." 


CH.  IV.]  CONSOLIDATION  OF  STKATA.  33 

There  are  also  lagoons  at  the  mouths  of  many  rivers,  as  the  Nile  and 
Mississippi,  which  are  divided  off  by  bars  of  sand  from  the  sea,  and 
which  are  filled  with  salt  and  fresh  water  by  turns.  They  often  commu- 
nicate exclusively  with  the  river  for  months,  years,  or  even  centuries ; 
and  then  a  breach  being  made  in  the  bar  of  sand,  they  are  for  long  pe- 
riods filled  with  salt  water. 

The  Lym-Fiord  in  Jutland  offers  an  excellent  illustration  of  analogous 
changes  ;  for,  in  the  course  of  the  last  thousand  years,  the  western  ex- 
tremity of  this  long  frith,  which  is  120  miles  in  length,  including  its 
windings,  has  been  four  times  fresh  .and  four  times  salt,  a  bar  of  sand 
between  it  and  the  ocean  having  been  as  often  formed  and  removed. 
The  last  irruption  of  salt  water  happened  in  1824,  when  the  North  Sea 
entered,  killing  all  the  freshwater  shells,  fish,  and  plants  ;  and  from  that 
time  to  the  present,  the  sea-weed  Fucus  vesiculosus,  together  with  oys- 
ters and  other  marine  mollusca,  have  succeeded  the  Cyclas,  Lymnea, 
Paludina,  and  Charce* 

But  changes  like  these  in  the  Lym-Fiord,  and  those  before  mentioned 
as  occurring  at  the  mouths  of  great  rivers,  will  only  account  for  some 
cases  of  marine  deposits  of  partial  extent  resting  on  freshwater  strata. 
When  we  find,  as  in  the  southeast  of  England,  a  great  series  of  fresh- 
water beds,  1000  feet  in  thickness,  resting  upon  marine  formations  and 
again  covered  by  other  rocks,  such  as  the  cretaceous,  more  than  1000 
feet  thick,  and  of  deep-sea  origin,  we  shall  find  it  necessary  to  seek  for  a 
different  explanation  of  the  phenomena.! 


CHAPTER  IV. 


CONSOLIDATION    OF    STRATA    AND    PETRIFACTION    OF    FOSSILS. 

Chemical  and  mechanical  deposits — Cementing  together  of  particles — Hardening 
by  exposure  to  air — Concretionary  nodules — Consolidating  effects  of  pressure — 
Mineralization  of  organic  remains — Impressions  and  casts  how  formed — Fossil 
•wood — Goppert's  experiments — Precipitation  of  stony  matter  most  rapid  where 
putrefaction  is  going  on — Source  of  lime  in  solution — Silex  derived  from  de- 
composition of  felspar — Proofs  of  the  lapidification  of  some  fossils  soon  after 
burial,  of  others  when  much  decayed. 

HAVING  spoken  in  the  preceding  chapters  of  the  characters  of  sedi- 
mentary formations,  both  as  dependent  on  the  deposition  of  inorganic 
matter  and  the  distribution  of  fossils,  I  may  next  treat  of  the  consolidation 
of  stratified  rocks,  and  the  petrifaction  of  imbedded  organic  remains. 

Chemical  and  mechanical  deposits. — A  distinction  has  been  made  by 

*  See  Principles,  Index,  "  Lym-Fiord." 

f  Sec  below,  Chap.  XVIII.,  on  the  Wealden. 


34  CONSOLIDATION  OF  STRATA.  [On.  IV. 

geologists  between  deposits  of  a  chemical,  and  those  of  a  mechanical, 
origin.  By  the  latter  name  are  designated  beds  of  mud,  sand,  or  peb- 
bles produced  by  the  action  of  running  water,  also  accumulations  of 
stones  and  scoriae  thrown  out  by  a  volcano,  which  have  fallen  into  their 
present  place  by  the  force  of  gravitation.  But  the  matter  which  forms 
a  chemical  deposit  has  not  been  mechanically  suspended  in  water,  but  in 
a  state  of  solution  until  separated  by  chemical  action.  In  this  manner 
carbonate  of  lime  is  often  precipitated  upon  the  bottom  of  lakes  and 
seas  in  a  solid  form,  as  may  be  well  seen  in  many  parts  of  Italy,  where 
mineral  springs  abound,  and  where  the  calcareous  stone,  called  travertin, 
is  deposited.  In  these  springs  the  lime  is  usually  held  in  solution  by  an 
excess  of  carbonic,  acid,  or  by  heat  if  it  be  a  hot  spring,  until  the  water, 
on  issuing  from  the  earth,  cools  or  loses  part  of  its  acid.  The  calcareous 
matter  then  falls  down  in  a  solid  state,  incrusting  shells,  fragments  of 
wood  and  leaves,  and  binding  them  together.* 

In  coral  reefs,  large  masses  of  limestone  are  formed  by  the  stony  skel- 
etons of  zoophytes ;  and  these,  together  with  shells,  become  cemented 
together  by  carbonate  of  lime,  part  of  which  is  probably  furnished  to 
the  sea-water  by  the  decomposition  of  dead  corals.  Even  shells  of  which 
the  animals  are  still  living,  on  these  reefs,  are  very  commonly  found  to 
be  incrusted  over  with  a  hard  coating  of  limestone.f 

If  sand  and  pebbles  are  carried  by  a  river  into  the  sea,  and  these 
are  bound  together  immediately  by  carbonate  of  lime,  the  deposit 
may  be  described  as  of  a  mixed  origin,  partly  chemical,  and  partly 
mechanical. 

Now,  the  remarks  already  made  in  Chapter  II.  on  the  original  hori- 
zontality  of  strata  are  strictly  applicable  to  mechanical  deposits,  and 
only  partially  to  those  of  a  mixed  nature.  Such  as  are  purely  chemical 
may  be  formed  on  a  very  steep  slope,  or  may  even  incrust  the  vertical 
walls  of  a  fissure,  and  be  of  equal  thickness  throughout ;  but  such  de- 
posits are  of  small  extent,  and  for  the  most  part  confined  to  vein-stones. 

Cementing  of  particles. — It  is  chiefly  in  the  case  of  calcareous  rocks 
that  solidification  takes  place  at  the  time  of  deposition.  But  there  are 
many  deposits  in  which  a  cementing  process  comes  into  operation  long 
afterwards.  We  may  sometimes  observe,  where  the  water  of  ferruginous 
or  calcareous  springs  has  flowed  through  a  bed  of  sand  or  gravel,  that 
iron  or  carbonate  of  lime  has  been  deposited  in  the  interstices  between 
the  grains  or  pebbles,  so  that  in  certain  places  the  whole  has  been  bound 
together  into  a  stone,  the  same  set  of  strata  remaining  in  other  parts 
loose  and  incoherent. 

Proofs  of  a  similar  cementing  action  are  seen  in  a  rock  at  Kelloway 
in  Wiltshire.  A  peculiar  band  of  sandy  strata,  belonging  to  the  group 
called  Oolite  by  geologists,  may  be  traced  through  several  counties,  the 
sand  being  for  the  most  part  loose  and  unconsolidated,  but  becoming 

*  See  Principles,  Index,  "  Calcareous  Springs,"  <fec. 
\  Ibid.     "  Travertin,"  "  Coral  Reefs,"  <fec. 


Cu.  IV.]  CONSOLIDATION   OF   STRATA.  35 

stony  near  Kelloway.  In  this  district  there  are  numerous  fossil  shells 
which  have  decomposed,  having  for  the  most  part  left  only  their  casts. 
The  calcareous  matter  hence  derived  has  evidently  served,  at  some  former 
period,  as  a  cement  to  the  siliceous  grains  of  sand,  and  thus  a  solid  sand- 
stone has  been  produced.  If  we  take  fragments  of  many  other  argilla- 
ceous grits,  retaining  the  casts  of  shells,  and  plunge  them  imto  dilute 
muriatic  or  other  acid,  we  see  them  immediately  changed  into  common 
sand  and  mud  ;  the  cement  of  lime  derived  from  the  shells,  having  been 
dissolved  by  the  acid. 

Traces  of  impressions  and  casts  are  often  extremely  faint.  In  some 
loose  sands  of  recent  date  we  meet  with  shells  in  so  advanced  a  stage  of 

O 

decomposition  as  to  crumble  into  powder  when  touched.  It  is  clear  that 
water  percolating  such  strata  may  soon  remove  the  calcareous  matter  of 
the  shell ;  and,  unless  circumstances  cause  the  carbonate  of  lime  to  be 
again  deposited,  the  grains  of  sand  will  not  be  cemented  together ;  in 
which  case  no  memorial  of  the  fossil  will  remain.  The  absence  of  or- 
ganic remains  from  many  aqueous  rocks  may  be  thus  explained ;  but 
we  may  presume  that  in  many  of  them  no  fossils  were  ever  imbedded, 
as  there  are  extensive  tracts  on  the  bottoms  of  existing  seas  even  of 
moderate  depth  on  which  no  fragment  of  shell,  coral,  or  other  living 
creature  can  be  detected  by  dredging.  On  the  other  hand,  there  are 
depths  where  the  zero  of  animal  life  has  been  approached  ;  as,  for  ex- 
ample, in  the  Mediterranean,  at  the  depth  of  about  230  fathoms,  accord- 
ing to  the  researches  of  Prof.  E.  Forbes.  In  the  ^Egean  Sea  a  deposit 
of  yellowish  mud  of  a  very  uniform  character,  and  closely  resembling 
chalk,  is  going  on  in  regions  below  230  fathoms,  and  this  formation 
must  be  wholly  devoid  of  organic  remains.* 

In  what  manner  silex  and  carbonate  of  lime  may  become  widely  dif- 
fused in  small  quantities  through  the  waters  which  permeate  the  earth's 
crust  will  be  spoken  of  presently,  when  the  petrifaction  of  fossil  bodies 
is  considered;  but  I  may  remark  here  that  such  waters  are  always 
passing  in  the  case  of  thermal  springs  from  hotter  to  colder  parts  of  the 
interior  of  the  earth  ;  and  as  often  as  the  temperature  of  the  solvent  is 
lowered,  mineral  matter  has  a  tendency  to  separate  from  it  and  solidify. 
Thus  a  stony  cement  is  often  supplied  to  sand,  pebbles,  or  any  fragment- 
ary mixture.  In  some  conglomerates,  like  the  pudding-stone  of  Hertford- 
shire (a  Lower  Eocene  deposit J,  pebbles  of  flint  and  grains  of  sand  are 
united  by  a  siliceous  cement  so  firmly,  that  if  a  block  be  fractured  the 
rent  passes  as  readily  through  the  pebbles  as  through  the  cement. 

It  is  probable  that  many  strata  became  solid  at  the  time  when  they 
emerged  from  the  waters  in  which  they  were  deposited,  and  when  they 
first  formed  a  part  of  the  dry  land.  A  well-known  fact  seems  to  con- 
firm this  idea  :  by  far  the  greater  number  of  the  stones  used  for  building 
and  road-making  are  much  softer  when  first  taken  from  the  quarry 
than  after  they  have  been  long  exposed  to  the  air ;  and  these,  when  once 

*  Report  Brit.  Ass.  1843,  p.  178. 


36  CONSOLIDATION  OF  STKATA.  [On.  IV. 

dried,  may  afterwards  be  immersed  for  any  length  of  time  in  water 
without  becoming  soft  again.  Hence  it  is  found  desirable  to  shape  the 
stones  which  are  to  be  used  in  architecture  while  they  are  yet  soft  and 
wet,  and  while  they  contain  their  "  quarry- water,"  as  it  is  called ;  also  to 
break  up  stone  intended  for  roads  when  soft,  and  then  leave  it  to  dry  in 
the  air  for  months  that  it  may  harden.  Such  induration  may  perhaps 
be  accounted  for  by  supposing  the  water,  which  penetrates  the  minutest 
pores  of  rocks,  to  deposit,  on  evaporation,  carbonate  of  lime,  iron,  silex, 
and  other  minerals  previously  held  in  solution,  and  thereby  to  fill  up  the 
pores  partially.  These  particles,  on  crystallizing,  would  not  only  be 
themselves  deprived  of  freedom  of  motion,  but  would  also  bind  together 
other  portions  of  the  rock  which  before  were  loosely  aggregated.  On 
the  same  principle  wet  sand  and  mud  become  as  hard  as  stone  when 
frozen ;  because  one  ingredient  of  the  mass,  namely,  the  water,  has  crys- 
tallized, so  as  to  hold  firmly  together  all  the  separate  particles  of  which 
the  loose  mud  and  sand  were  composed. 

Dr.  MacCulloch  mentions  a  sandstone  in  Skye,  which  may  be  moulded 
like  dough  when  first  found  ;  and  some  simple  minerals,  which  are  rigid 
and  as  hard  as  glass  in  our  cabinets,  are  often  flexible  and  soft  in  their 
native  beds ;  this  is  the  case  with  asbestos,  sahlite,  tremolite,  and 
chalcedony,  and  it  is  reported  also  to  happen  in  the  case  of  the 
beryl.* 

The  marl  recently  deposited  at  the  bottom  of  Lake  Superior,  in  North 
America,  is  soft,  and  often  filled  with  freshwater  shells ;  but  if  a  piece 
be  taken  up  and  dried,  it  becomes  so  hard  that  it  can  only  be  broken  by 
a  smart  blow  of  the  hammer.  If  the  lake  therefore  was  drained,  such 
a  deposit  would  be  found  to  consist  of  strata  of  marlstone,  like  that 
observed  in  many  ancient  European  formations,  and  like  them  contain- 
ing freshwater  shells. 

It  is  probable  that  some  of  the  heterogeneous  materials  which  rivers 
transport  to  the  sea  may  at  once  set  under  water,  like  the  artificial  mix- 
ture called  pozzolana,  which  consists  of  fine  volcanic  sand  charged  with 
about  20  per  cent,  of  oxide  of  iron,  and  the  addition  of  a  small  quantity 
of  lime.  This  substance  hardens,  and  becomes  a  solid  stone  in  water, 
and  was  used  by  the  Romans  in  constructing  the  foundations  of  build- 
ings in  the  sea. 

Consolidation  in  these  cases  is  brought  about  by  the  action  of  chemical 
affinity  on  finely  comminuted  matter  previously  suspended  in  water. 
After  deposition  similar  particles  seem  to  exert  a  mutual  attraction  on 
each  other,  and  congregate  together  in  particular  spots,  forming  lumps, 
nodules,  and  concretions.  Thus  in  many  argillaceous  deposits  there  are 
calcareous  balls,  or  spherical  concretions,  ranged  in  layers  parallel  to  the 
general  stratification  ;  an  arrangement  which  took  place  after  the  shale 
or  marl  had  been  thrown  down  in  successive  laminae  ;  for  these  laminae 

*  Dr.  MacCulloch,  Syst.  of  Geol.  vol.  i.  p.  123, 


CH.  IV.] 


COXCRETTOXARY   STRUCTURE. 


37 


Fig.  55. 


Calcareous  nodules  in  Lias. 


Fig,  56. 


Spheroidal  concretions  in  magnesian 
limestone. 


are  often  traced  in  the  concretions,  remaining  parallel  to  those  of  the  sur- 
rounding unconsolidated  rock.  (See  fig.  55.)  Such  nodules  of  lime- 
stone have  often  a  shell  or  other  foreign 
body  in  the  centre.* 

Among  the  most  remarkable  exam- 
ples of  concretionary  structure  are  those 
described  by  Professor  Sedgwick  as 
abounding  in  the  magnesian  limestone 
of  the  north  of  England.  The  spherical  balls  are  of  various  sizes,  from 
that  of  a  pea  to  a  diameter  of  several  feet,  and  they  have  both  a  con- 
centric and  radiated  structure,  while  at  the  same  time  the  laminae  of 
original  deposition  pass  uninterruptedly  through  them.  In  some  cliffs 
this  limestone  resembles  a  great  irregular  pile  of  cannon  balls.  Some 
of  the  globular  masses  have  their  centre  in  one  stratum,  while  a  portion 
of  their  exterior  passes  through  to  the  stratum  above  or  below.  Thus 
the  larger  spheroid  in  the  annexed  section  (fig.  56)  passes  from  the 

stratum  b  upwards  into  a.  In  this  in- 
stance we  must  suppose  the  deposition  of 
a  series  of  minor  layers,  first  forming  the 
stratum  6,  and  afterwards  the  incumbent 
stratum  a  ;  then  a  movement  of  the  par- 
ticles took  place,  and  the  carbonates  of 
lime  and  magnesia  separated  from  the 
more  impure  and  mixed  matter,  forming  the  still  unconsolidated  parts  of 
the  stratum.  Crystallization,  beginning  at  the  centre,  must  have  gone 
on  forming  concentric  coats,  around  the  original  nucleus  without  inter- 
fering with  the  laminated  structure  of  the  rock. 

When  the  particles  of  rocks  have  been  thus  rearranged  by  chemical 
forces,  it  is  sometimes  difficult  or  impossible  to  ascertain  whether  certain 
lines  of  division  are  due  to  original  deposition  or  to  the  subsequent  ag- 
gregation of  similar  particles.  Thus  suppose  three  strata  of  grit,  A,  B, 

C,  are  charged  unequally  with  calcareous 
matter,  and  that  B  is  the  most  calcareous. 
If  consolidation  takes  place  in  B,  the  con- 
cretionary action  may  spread  upwards 
into  a  part  of  A,  where  the  carbonate  of 
lime  is  more  abundant  than  in  the  rest ;  so  that  a  mass  d,  e,  /,  forming 
a  portion  of  the  superior  stratum,  becomes  united  with  B  into  one  solid 
mass  of  stone.  The  original  line  of  division  c?,  e,  being  thus  effaced,  the 
line  d,  /,  would  generally  be  considered  as  the  surface  of  the  bed  B, 
though  not  strictly  a  true  plane  of  stratification. 

Pressure  and  heat. — When  sand  and  mud  sink  to  the  bottom  of  a 
deep  sea,  the  particles  are  not  pressed  down  by  the  enormous  weight  of 
the  incumbent  ocean  ;  for  the  water,  which  becomes  mingled  with  the 
sand  and  mud,  resists  pressure  with  a  force  equal  to  that  of  the  column 


Fig.  57. 


*  De  la  Beche,  Geol.  Researches,  p.  95,  and  Geol.  Observer  (1851),  p.  686. 


38  MINERALIZATION  OF  [Cn.  IV. 

of  fluid  above.  The  same  happens  in  regard  to  organic  remains  which 
are  filled  with  water  under  great  pressure  as  they  sink,  otherwise  they 
would  be  immediately  crushed  to  pieces  and  flattened.  Nevertheless,  if 
the  materials  of  a  stratum  remain  in  a  yielding  state,  and  do  not  set  or 
solidify,  they  will  be  gradually  squeezed  down  by  the  weight  of  other 
materials  successively  heaped  upon  them,  just  as  soft  clay  or  loose  sand 
on  which  a  house  is  built  may  give  way.  By  such  downward  pressure 
particles  of  clay,  sand,  and  marl,  may  become  packed  into  a  smaller 
space,  and  be  made  to  cohere  together  permanently. 

Analogous  effects  of  condensation  may  arise  when  the  solid  parts  of 
the  earth's  crust  are  forced  in  various  directions  by  those  mechanical 
movements  afterwards  to  be  described,  by  which  strata  have  be^n  bent, 
broken,  and  raised  above  the  level  of  the  sea.  Rocks  of  more  yielding 
materials  must  often  have  been  forced  against  others  previously  consol- 
idated, and,  thus  compressed,  may  have  acquired  a  new  structure.  A 
recent  discovery  may  help  us  to  comprehend  how  fine  sediment  derived 
from  the  detritus  of  rocks  may  be  solidified  by  mere  pressure.  The 
graphite  or  "  black  lead"  of  commerce  having  become  very  scarce,  Mr. 
Brockedon  contrived  a  method  by  which  the  dust  of  the  purer  portions 
of  the  mineral  found  in  Borrowdale  might  be  recomposed  into  a  mass  as 
dense  and  compact  as  native  graphite.  The  powder  of  graphite  is  first 
carefully  prepared  and  freed  from  air,  and  placed  under  a  powerful  press 
on  a  strong  steel  die,  with  air-tight  fittings.  It  is  then  struck  several 
blows,  each  of  a  power  of  1000  tons  ;  after  which  operation  the  powdei 
is  so  perfectly  solidified  that  it  can  be  cut  for  pencils,  and  exhibits  when 
broken  the  same  texture  as  native  graphite. 

But  the  action  of  heat  at  various  depths  in  the  earth  is  probably  the 
most  powerful  of  all  causes  in  hardening  sedimentary  strata.  To  this 
subject  I  shall  refer  again  when  treating  of  the  inetamorphic  rocks,  and 
of  the  slaty  and  jointed  structure. 

Mineralization  of  organic  remains. — The  changes  which  fossil  organic 
bodies  have  undergone  since  they  were  first  imbedded  in  rocks,  throw 
much  light  on  the  consolidation  of  strata.  Fossil  shells  in  some  modern 
deposits  have  been  scarcely  altered  in  the  course  of  centuries,  having 
simply  lost  a  part  of  their  animal  matter.  But  in  other  cases  the  shell 
has  disappeared,  and  left  an  impression  only  of  its  exterior,  or  a  cast  of 
its  interior  form,  or  thirdly,  a  cast  of  the  shell  itself,  the  original  matter 
of  which  has  been  removed.  These  different  forms  of  fossilization  may 
easily  be  understood  if  we  examine  the  mud  recently  thrown  out  from  a 
pond  or  canal  in  which  there  are  shells.  If  the  mud  be  argillaceous,  it 
acquires  consistency  on  drying,  and  on  breaking  open  a  portion  of  it  we 
find  that  each  shell  has  left  impressions  of  its  external  form.  If  we  then 
remove  the  shell  itself,  we  find  within  a  solid  nucleus  of  clay,  having  the 
form  of  the  interior  of  the  shell.  This  form  is  often  very  different  from 
that  of  the  outer  shell.  Thus  a  cast  such  as  a,  fig.  58,  commonly  called 
a  fossil  screw,  would  never  be  suspected  by  an  inexperienced  conch  ologist 
to  be  the  internal  shape  of  the  fossil  univalve,  6,  fig.  58.  Nor  should 


CH.  IV.]  ORGANIC   REMAINS.  39 

we  have  imagined  at  first  sight  that  the  shell  a  and  the  cast  6,  fig.  59, 
were  different  parts  of  the  same  fossil.     The  reader  will  observe,  in  the 

Fig.  89. 


Pha&ianfUa  ffeddingtonenxis,  Pleurotom  aria  A  n  ylica  and 

and  cast  of  the  same.    Coral  Eag.  cast    Lias. 

last-mentioned  figure  (6,  fig.  59),  that  an  empty  space  shaded  dark,  which 
the  shell  itself  once  occupied,  now  intervenes  between  the  enveloping 
stone  and  the  cast  of  the  smooth  interior  of  the  whorls.  In  such  cases 
the  shell  has  been  dissolved  and  the  component  particles  removed  by 
water  percolating  the  rock.  If  the  nucleus  were  taken  out  a  hollow 
mould  would  remain,  on  which  the  external  form  of  the  shell  with  its 
tubercles  and  striae,  as  seen  in  a,  fig.  59,  would  be  seen  embossed.  Now 
if  the  space  alluded  to  between  the  nucleus  and  the  impression,  instead 
of  being  left  empty,  has  been  filled  up  with  calcareous  spar,  flint,  py- 
rites, or  other  mineral,  we  then  obtain  from  the  mould  an  exact  cast  both 
of  the  external  and  internal  form  of  the  original  shell.  In  this  manner 
silicified  casts  of  shells  have  been  formed ;  and  if  the  mud  or  sand  of 
the  nucleus  happen  to  be  incoherent,  or  soluble  in  acid,  we  can  then  pro- 
cure in  flint  an  empty  shell,  which  in  shape  is  the  exact  counterpart  of 
the  original.  This  cast  may  be  compared  to  a  bronze  statue,  representing 
merely  the  superficial  form,  and  not  the  internal  organization ;  but  there 
is  another  description  of  petrifaction  by  no  means  uncommon,  and  of  a 
much  more  wonderful  kind,  which  may  be  compared  to  certain  anatom- 
ical models  in  wax,  where  not  only  the  outward  forms  and  features,  but 
the  nerves,  blood-vessels,  and  other  internal  organs  are  also  shown. 
Thus  we  find  corals,  originally  calcareous,  in  which  not  only  the  general 
shape,  but  also  the  minute  and  complicated  internal  organization  are  re- 
tained in  flint. 

Such  a  process  of  petrifaction  is  still  more  remarkably  exhibited  in 
fossil  wood,  in  which  we  often  perceive  not  only  the  rings  of  annual 
growth,  but  all  the  minute  vessels  and  medullary  rays.  Many  of  the 
minute  cells  and  fibres  of  plants,  and  even  those  spiral  vessels  which  in 
the  living  vegetable  can  only  be  discovered  by  the  microscope,  are  pre- 
served. Among  many  instances,  I  may  mention  a  fossil  tree,  72  feet  in 
length,  found  at  Gosforth  near  Newcastle,  in  sandstone  strata  associated 
with  coal.  By  cutting  a  transverse  slice  so  thin  as  to  transmit  light, 
and  magnifying  it  about  fifty-five  times,  the  texture  seen  in  fig.  60  is  ex- 


4.0  MINEEALIZATIOX   OF  [On.  IV. 

hibited.     A  texture  equally  minute  and  complicated  has  been  observed 
in  the  wood  of  large  trunks  of  fossil  trees  found 
in  the  Craigleith  quarry  near  Edinburgh,  where 
the  stone  was  not  in  the  slightest  degree  siliceous, 
but  consisted  chiefly  of  carbonate  of  lime,  with 
oxide  of  iron,  alumina,  and  carbon.     The  parallel 
rows  of  vessels  here  seen  are  the  rings  of  an- 
nual growth,  but  in  one  part  they  are  imperfectly 
T7x7ure~o7a  treT^m'the    Preserved,  the  wood   having  probably  decayed 
coal  strata,  magnified.   (Wi-     before  the  mineralizing;  matter  had  penetrated  to 

tham.)    Transverse  section. 

that  portion  ot  the  tree. 

In  attempting  to  explain  the  process  of  petrifaction  in  such  cases,  we 
may  first  assume  that  strata  are  very  generally  permeated  by  water 
charged  with  minute  portions  of  calcareous,  siliceous,  and  other  earths 
in  solution.  In  what  manner  they  become  so  impregnated  will  be  after- 
wards considered.  If  an  organic  substance  is  exposed  in  the  open  air 
to  the  action  of  the  sun  and  rain,  it  will  in  time  putrefy,  or  be  dissolved 
into  its  component  elements,  which  consist  chiefly  of  oxygen,  hydrogen, 
and  carbon.  These  will  readily  be  absorbed  by  the  atmosphere  or  be 
washed  away  by  rain,  so  that  all  vestiges  of  the  dead  animal  or  plant 
disappear.  But  if  the  same  substances  be  submerged  in  water,  they  de- 
compose more  gradually ;  and  if  buried  in  earth,  still  more  slowly,  as  in 
the  familiar  example  of  wooden  piles  or  other  buried  timber.  Now,  if 
as  fast  as  each  particle  is  set  free  by  putrefaction  in  a  fluid  or  gaseous 
state,  a  particle  equally  minute  of  carbonate  of  lime,  flint,  or  other  min- 
eral, is  at  hand  and  ready  to  be  precipitated,  we  may  imagine  this  inor- 
ganic matter  to  take  the  place  just  before  left  unoccupied  by  the  organic 
molecule.  In  this  manner  a  cast  of  the  interior  of  certain  vessels  may 
first  be  taken,  and  afterwards  the  more  solid  walls  of  the  same  may 
decay  and  suffer  a  like  transmutation.  Yet  when  the  whole  is  lapidified, 
it  may  not  form  one  homogeneous  mass  of  stone  or  metal.  Some  of  the 
original  ligneous,  osseous,  or  other  organic  elements  may  remain  mingled 
in  certain  parts,  or  the  lapidifying  substance  itself  may  be  differently 
colored  at  different  times,  or  so  crystallized  as  to  reflect  light  differ- 
ently, and  thus  the  texture  of  the  original  body  may  be  faithfully 
exhibited. 

The  student  may  perhaps  ask  whether,  on  chemical  principles,  we  have 
any  ground  to  expect  that  mineral  matter  will  be  thrown  down  precisely 
in  those  spots  where  organic  decomposition  is  in  progress  ?  The  following 
curious  experiments  may  serve  to  illustrate  this  point.  Professor  Gop- 
pert  of  Breslau  attempted  recently  to  imitate  the  natural  process  of  pet- 
rifaction. For  this  purpose  he  steeped  a  variety  of  animal  and  vegetable 
substances  in  waters,  some  holding  siliceous,  others  calcareous,  others 
metallic  matter  in  solution.  He  found  that  in  the  period  of  a  few  weeks, 
or  even  days,  the  organic  bodies  thus  immersed  were  mineralized  to  a 
certain  extent.  Thus,  for  example,  thin  vertical  slices  of  deal,  taken 
from  the  Scotch  fir  (Pinus  sylvestris),  were  immersed  in  a  moderately 


Ca  IV.]  ORGANIC  REMAINS.  41 

strong  solution  of  sulphate  of  iron.  When  they  had  been  thoroughly 
soaked  in  the  liquid  for  several  days  they  were  dried  and  exposed  to  a 
red-heat  until  the  vegetable  matter  was  burnt  up  and  nothing  remained 
but  an  oxide  of  iron,  which  was  found  to  have  taken  the  form  of  the 
deal  so  exactly  that  casts  even  of  the  dotted  vessels  peculiar  to  this  fam- 
ily of  plants  were  distinctly  visible  under  the  microscope. 

Another  accidental  experiment  has  been  recorded  by  Mr.  Pepys  in  the 
Geological  Transactions.*  An  earthen  pitcher  containing  several  quarts 
of  sulphate  of  iron  had  remained  undisturbed  and  unnoticed  for  about  a 
twelvemonth  in  the  laboratory.  At  the  end  of  this  time  when  the  liquor 
was  examined  an  oily  appearance  was  observed  on  the  surface,  and  a 
yellowish  powder,  which  proved  to  be  sulphur,  together  with  a  quantity 
of  small  hairs.  At  the  bottom  were  discovered  the  bones  of  several  mice 
in  a  sediment  consisting  of  small  grains  of  pyrites,  others  of  sulphur, 
others  of  crystallized  green  sulphate  of  iron,  and  a  black  muddy  oxide 
of  iron.  It  was  evident  that  some  mice  had  accidentally  been  drowned  in 
the  fluid,  and  by  the  mutual  action  of  the  animal  matter  and  the  sulphate 
of  iron  on  each  other,  the  metallic  sulphate  had  been  deprived  of  its  ox- 
ygen ;  hence  the  pyrites  and  the  other  compounds  were  thrown  down. 
Although  the  mice  were  not  mineralized,  or  turned  into  pyrites,  the  phe- 
nomenon shows  how  mineral  waters,  charged  with  sulphate  of  iron,  may 
be  deoxydated  on  coming  in  contact  with  animal  matter  undergoing  pu- 
trefaction, so  that  atom  after  atom  of  pyrites  may  be  precipitated,  and 
ready,  under  favorable  circumstances,  to  replace  the  oxygen,  hydrogen, 
and  carbon  into  which  the  original  body  would  be  resolved. 

The  late  Dr.  Turner  observes,  that  when  mineral  matter  is  in  a 
"  nascent  state,"  that  is  to  say,  just  liberated  from  a  previous  state  of 
chemical  combination,  it  is  most  ready  to  unite  with  other  matter,  and 
form  a  new  chemical  compound.  Probably  the  particles  or  atoms  just 
set  free  are  of  extreme  minuteness,  and  therefore  move  more  freely,  and 
are  more  ready  to  obey  any  impulse  of  chemical  affinity.  Whatever  be 
the  cause,  it  clearly  follows,  as  before  stated,  that  where  organic  matter 
newly  imbedded  in  sediment  is  decomposing,  there  will  chemical  changes 
take  place  most  actively. 

An  analysis  was  lately  made  of  the  water  which  was  flowing  off  from 
the  rich  mud  deposited  by  the  Hooghly  river  in  the  Delta  of  the  Ganges 
after  the  annual  inundation.  This  water  was  found  to  be  highly  charged 
with  carbonic  acid  gas  holding  lime  in  solution.f  Now  if  newly- 
deposited  mud  is  thus  proved  to  be  permeated  by  mineral  matter  in  a 
state  of  solution,  it  is  not  difficult  to  perceive  that  decomposing  organic 
bodies,  naturally  imbedded  in  sediment,  may  as  readily  become  petrified 
as  the  substances  artificially  immersed  by  Professor  Goppert  in  various 
fluid  mixtures. 

Tt  is  well  known  that  the  water  of  springs,  or  that  which  is  continually 

*  Vol.  i.  p.  399,  first  series. 

\  Piddington,  Asiat,  Research,  vol.  xviii.  p.  226. 


4:2  FLINT  OF  SILICIFIED  FOSSILS.  [On.  IV. 

percolating  the  earth's  crust,  is  rarely  free  from  a  slight  admixture  either 
of  iron,  carbonate  of  lime,  sulphur,  silica,  potash,  or  some  other  earthy, 
alkaline,  or  metallic  ingredient.  Hot  springs  in  particular  are  copiously 
charged  with  one  or  more  of  these  elements ;  and  it  is  only  in  their 
waters  that  silex  is  found  in  abundance.  In  certain  cases,  therefore, 
especially  in  volcanic  regions,  we  may  imagine  the  flint  of  silicified 
wood  and  corals  to  have  been  supplied  by  the  waters  of  thermal  springs. 
In  other  instances,  as  in  tripoli,  it  may  have  been  derived  in  great  part,  if 
not  wholly,  from  the  decomposition  of  diatomaceae,  sponges,  and  othei 
bodies.  But  even  if  this  be  granted,  we  have  still  to  inquire  whence  a  lake 
or  the  ocean  can  be  constantly  replenished  with  the  calcareous  and  siliceous 
matter  so  abundantly  withdrawn  from  it  by  the  secretions  of  living  beings. 

In  regard  to  carbonate  of  lime  there  is  no  difficulty,  because  not 
only  are  calcareous  springs  very  numerous,  but  even  rain-water,  when 
it  falls  on  ground  where  vegetable  matter  is  decomposing,  may  be- 
come so  charged  with  carbonic  acid  as  to  acquire  a  power  of  dis- 
solving a  minute  portion  of  the  calcareous  rocks  over  which  it  flows. 
Hence  marine  corals  and  mollusca  may  be  provided  by  rivers  with 
the  materials  of  their  shells  and  solid  supports.  But  pure  silex,  even 
when  reduced  to  the  finest  powder  and  boiled,  is  insoluble  in  water, 
except  at  very  high  temperatures.  Nevertheless  Dr.  Turner  has  well  ex- 
plained, in  an  essay  on  the  chemistry  of  geology,*  how  the  decomposi- 
tion of  felspar  may  be  a  source  of  silex  in  solution.  He  has  remarked 
that  the  siliceous  earth,  which  constitutes  more  than  half  the  bulk  of 
felspar,  is  intimately  combined  with  alumine,  potash,  and  some  other 
elements.  The  alkaline  matter  of  the  felspar  has  a  chemical  affinity  for 
water,  as  also  for  the  carbonic  acid  which  is  more  or  less  contained  in 
the  waters  of  most  springs.  The  water  therefore  carries  away  alkaline 
matter,  and  leaves  behind  a  clay  consisting  of  alumine  and  silica.  But 
this  residue  of  the  decomposed  mineral,  which  in  its  purest  state  is  called 
porcelain  clay,  is  found  to  contain  a  part  only  of  the  silica  which  existed 
in  the  original  felspar.  The  other  part,  therefore,  must  have  been  dis- 
solved and  removed ;  and  this  can  be  accounted  for  in  two  ways  ;  first, 
because  silica  when  combined  with  an  alkali  is  soluble  in  water ;  sec- 
ondly, because  silica  in  what  is  technically  called  its  nascent  state  is  also 
soluble  in  water.  Hence  an  endless  supply  of  silica  is  afforded  to  rivers 
and  the  waters  of  the  sea.  For  the  felspathic  rocks  are  universally  dis- 
tributed, constituting,  as  they  do,  so  large  a  proportion  of  the  volcanic, 
plutonic,  and  metamorphic  formations.  Even  where  they  chance  to  be 
absent  in  mass,  they  rarely  fail  to  occur  in  the  superficial  gravel  or  allu- 
vial deposits  of  the  basin  of  every  large  river. 

The  disintegration  of  mica  also,  another  mineral  which  enters  largely  in- 
to the  composition  of  granite  and  various  sandstones,  may  yield  silica  which 
may  be  dissolved  in  water,  for  nearly  half  of  this  mineral  consists  of  silica, 
combined  with  alumine,  potash,  and  about  a  tenth  part  of  iron.  The  ox- 
idation of  this  iron  in  the  air  is  the  principal  cause  of  the  waste  of  mica. 

*  Jam.  Ed.  New  Phil.  Journ.  No.  30,  p.  246. 


Cn.  IV.]  PKOCESS   OF   PETRIFACTION.  43 

We  have  still,  however,  much  to  learn  before  the  conversion  of  fossil 
bodies  into  stone  is  fully  understood.  Some  phenomena  seem  to  imply 
that  the  mineralization  must  proceed  with  considerable  rapidity,  for 
stems  of  a  soft  and  succulent  character,  and  of  a  most  perishable  nature, 
are  preserved  in  flint ;  and  there  are  instances  of  the  complete  silicifica- 
tion  of  the  young  leaves  of  a  palm-tree  when  just  about  to  shoot  forth, 
and  in  that  state  which  in  the  West  Indies  is  called  the  cabbage  of  the 
palm.*  It  may,  however,  be  questioned  whether  in  such  cases  there 
may  not  have  been  some  antiseptic  quality  in  the  water  which  re- 
tarded putrefaction,  so  that  the  soft  parts  of  the  buried  substance  may 
have  remained  for  a  long  time  without  disintegration,  like  the  flesh  of 
bodies  imbedded  in  peat. 

Mr.  Stokes  has  pointed  out  examples  of  petrifactions  in  which  the 
more  perishable,  and  others  where  the  more  durable  portions  of  wood 
are  preserved.  These  variations,  he  suggests,  must  doubtless  have  de- 
pended on  the  time  when  the  lapidifying  mineral  was  introduced.  Thus, 
in  certain  silicified  stems  of  palm-trees,  the  cellular  tissue,  that  most  de- 
structible part,  is  in  good  condition,  while  all  signs  of  the  hard  woody 
fibre  have  disappeared,  the  spaces  once  occupied  by  it  being  hollow  or 
filled  with  agate.  Here,  petrifaction  must  have  commenced  soon  after 
the  wood  was  exposed  to  the  action  of  moisture,  and  the  supply  of  min- 
eral matter  must  then  have  failed,  or  the  water  must  have  become  too 
much  diluted  before  the  woody  fibre  decayed.  But  when  this  fibre  is 
alone  discoverable,  we  must  suppose  that  an  interval  of  time  elapsed  be- 
fore the  commencement  of  lapidification,  during  which  the  cellular  tissue 
was  obliterated.  When  both  structures,  namely,  the  cellular  and  the 
woody  fibre,  are  preserved,  the  process  must  have  commenced  at  an 
early  period,  and  continued  without  interruption  till  it  was  completed 
throughout.f 

*  Stokes,  GeoL  Trans,  vol.  v.  p.  212,  second  series, 
f  Ibid. 


44  LAND  HAS  BEEN  RAISED,  [Cn.  V, 


CHAPTER  V. 

ELEVATION     OF     STRATA    ABOVE     THE     SEA HORIZONTAL    AND     INCLINED 

STRATIFICATION. 

Why  the  position  of  marine  strata,  above  the  level  of  the  sea,  should  be  referred 
to  the  rising  up  of  the  land,  not  to  the  going  down  of  the  sea — Upheaval  of 
extensive  masses  of  horizontal  strata — Inclined  and  vertical  stratification — An- 
ticlinal and  synclinal  lines — Bent  strata  in  east  of  Scotland — Theory  of  folding 
by  lateral  movement — Creeps — Dip  and  strike — Structure  of  the  Jura — Vari- 
ous forms  of  outcrop — Rocks  broken  by  flexure — Inverted  position  of  disturbed 
strata — Unconformable  stratification — Hutton  and  Playfair  on  the  same — Frac- 
tures of  strata — Polished  surfaces — Faults — Appearance  of  repeated  alterna- 
tions produced  by  them — Origin  of  great  faults. 

LAND  has  been  raised,  not  the  sea  lowered. — It  has  been  already  stated 
that  the  aqueous  rocks  containing  marine  fossils  extend  over  wide  conti- 
nental tracts,  and  are  seen  in  mountain  chains  rising  to  great  heights 
above  the  level  of  the  sea  (p.  4).  Hence  it  follows,  that  what  is  now  dry 
land  was  once  under  water.  But  if  we  admit  this  conclusion,  we  must 
imagine,  either  that  there  has  been  a  general  lowering  of  the  waters  of  the 
ocean,  or  that  the  solid  rocks,  once  covered  by  water,  have  been  raised 
up  bodily  out  of  the  sea,  and  have  thus  become  dry  land.  The  earlier 
geologists,  finding  themselves  reduced  to  this  alternative,  embraced  the 
former  opinion,  assuming  that  the  ocean  was  originally  universal,  and 
had  gradually  sunk  down  to  its  actual  level,  so  that  the  present  islands 
and  continents  were  left  dry.  It  seemed  to  them  far  easier  to  conceive 
that  the  water  had  gone  down,  than  that  solid  land  had  risen  upwards 
into  its  present  position.  It  was,  however,  impossible  to  invent  any  sat- 
isfactory hypothesis  to  explain  the  disappearance  of  so  enormous  a  body 
of  water  throughout  the  globe,  it  being  necessary  to  infer  that  the  ocean 
had  once  stood  at  whatever  height  marine  shells  might  be  detected.  It 
moreover  appeared  clear,  as  the  science  of  Geology  advanced,  that  certain 
spaces  on  the  globe  had  been  alternately  sea,  then  land,  then  estuary, 
then  sea  again,  and,  lastly,  once  more  habitable  land,  having  remained 
in  each  of  these  states  for  considerable  periods.  In  order  to  account  for 
such  phenomena,  without  admitting  any  movement  of  the  land  itself,  we 
are  required  to  imagine  several  retreats  and  returns  of  the  ocean  ;  and 
even  then  our  theory  applies  merely  to  cases  where  the  marine  strata 
composing  the  dry  land  are  horizontal,  leaving  unexplained  those  more 
common  instances  where  strata  are  inclined,  curved,  or  placed  on  their 
edges,  and  evidently  not  in  the  position  in  which  they  were  first 
deposited. 

Geologists,  therefore,  were  at  last  compelled  to  have  recourse  to  the 
other  alternative,  namely,  the  doctrine  that  the  solid  land  has  been  re- 
peatedly moved  upwards  or  downwards,  so  as  permanently  to  change  ita 


OH.  V.]  NOT  THE  SEA  LOWERED.  45 

position  relatively  to  the  sea.  There  are  several  distinct  grounds  for 
preferring  this  conclusion.  First,  it  will  account  equally  for  the  position 
of  those  elevated  masses  of  marine  origin  in  which  the  stratification  re- 
mains horizontal,  and  for  those  in  which  the  strata  are  disturbed,  broken, 
inclined,  or  vertical.  Secondly,  it  is  consistent  with  human  experience 
that  land  should  rise  gradually  in  some  places  and  be  depressed  in 
others.  Such  changes  have  actually  occurred  in  our  own  days,  and  are 
now  in  progress,  having  been  accompanied  in  some  cases  by  violent  con- 
vulsions, while  in  others  they  have  proceeded  so  insensibly,  as  to  have 
been  ascertainable  only  by  the  most  careful  scientific  observations,  made 
at  considerable  intervals  of  time.  On  the  other  hand,  there  is  no  evi- 
dence from  human  experience  of  a  lowering  of  the  sea's  level  in  any 
region,  and  the  ocean  cannot  sink  in  one  place  without  its  level  being 
depressed  all  over  the  globe. 

These  preliminary  remarks  will  prepare  the  reader  to  understand  the 
great  theoretical  interest  attached  to  all  facts  connected  with  the  position 
of  strata,  whether  horizontal  or  inclined,  curved  or  vertical. 

Now  the  first  and  most  simple  appearance  is  where  strata  of  marine 
origin  occur  above  the  level  of  the  sea  in  horizontal  position.  Such  are 
the  strata  which  we  meet  with  in  the  south  of  Sicily,,  filled  with  shells 
for  the  most  part  of  the  same  species  as  those  now  living  in  the  Mediter- 
ranean. Some  of  these  rocks  rise  to  the  height  of  more  than  2000  feet 
above  the  sea.  Other  mountain  masses  might  be  mentioned,  composed 
of  horizontal  strata  of  high  antiquity,  which  contain  fossil  remains  of 
animals  wholly  dissimilar  from  any  now  known  to  exist.  In  the  south 
of  Sweden,  for  example,  near  Lake  Wener,  the  beds  of  one  of  the  oldest 
of  the  fossiliferous  deposits,  namely,  that  formerly  called  Transition,  and 
now  Silurian,  by  geologists,  occur  in  as  level  a  position  as  if  they  had 
recently  formed  part  of  the  delta  of  a  great  river,  and  been  left  dry  on 
the  retiring  of  the  annual  floods.  Aqueous  rocks  of  about  the  same  age 
extend  for  hundreds  of  miles  over  the  lake-district  of  North  America, 
and  exhibit  in  like  manner  a  stratification  nearly  undisturbed.  The 
Table  Mountain  at  the  Cape  of  Good  Hope  is  another  example  of  highly 
elevated  yet  perfectly  horizontal  strata,  no  less  than  3500  feet  in  thick- 
ness, and  consisting  of  sandstone  of  very  ancient  date. 

Instead  of  imagining  that  such  fossiliferous  rocks  were  always  at  their 
present  level,  and  that  the  sea  was  once  high  enough  to  cover  them,  we 
suppose  them  to  have  constituted  the  ancient  bed  of  the  ocean,  and  that 
they  were  gradually  uplifted  to  their  present  height.  This  idea,  how- 
ever startling  it  may  at  first  appear,  is  quite  in  accordance,  as  before 
stated,  with  the  analogy  of  changes  now  going  on  in  certain  regions  of 
the  globe.  Thus,  in  parts  of  Sweden,  and  the  shores  and  islands  of  the 
Gulf  of  Bothnia,  proofs  have  been  obtained  that  the  land  is  experiencing, 
and  has  experienced  for  centuries,  a  slow  upheaving  movement.  Play- 
fair  argued  in  favor  of  this  opinion  in  1802  ;  and  in  1807,  Yon  Buch, 
after  his  travels  in  Scandinavia,  announced  his  conviction  that  a  rising 
of  the  land  was  in  progress.  Celsius  and  other  Swedish  writers  had, 


46  RISING-  AND  SINKING  OF  LAND.  [On.  V. 

a  century  before,  declared  their  belief  that  a  gradual  change  had,  for 
ages,  been  taking  place  in  the  relative  level  of  land  and  sea.  They  at- 
tributed the  change  to  a  fall  of  the  waters  both  of  the  ocean  and  the 
Baltic.  This  theory,  however,  has  now  been  refuted  by  abundant  evi- 
dence ;  for  the  alteration  of  relative  level  has  neither  been  universal  nor 
everywhere  uniform  in  quantity,  but  has  amounted,  in  some  regions,  to 
several  feet  in  a  century,  in  others  to  a  few  inches  ;  while  in  the  south- 
ernmost part  of  Sweden,  or  the  province  of  Scania,  there  has  been  actu- 
ally a  loss  instead  of  a  gain  of  land,  buildings  having  gradually  sunk 
below  the  level  of  the  sea.* 

It  appears,  from  the  observations  of  Mr.  Darwin  and  others,  that  very 
extensive  regions  of  the  continent  of  South  America  have  been  under- 
going slow  and  gradual  upheaval,  by  which  the  level  plains  of  Patagonia, 
covered  with  recent  marine  shells,  and  the  Pampas  of  Buenos  Ayres, 
have  been  raised  above  the  level  of  the  sea.f  On  the  other  hand,  the 
gradual  sinking  of  the  west  coast  of  Greenland,  for  the  space  of  more 
than  600  miles  from  north  to  south,  during  the  last  four  centuries,  has 
been  established  by  the  observations  of  a  Danish  naturalist,  Dr.  Pingel. 
And  while  these  proofs  of  continental  elevation  and  subsidence,  by  slow 
and  insensible  movements,  have  been  recently  brought  to  light,  the  evi- 
dence has  been  daily  strengthened  of  continued  changes  of  level  effected 
by  violent  convulsions  in  countries  where  earthquakes  are  frequent.  There 
the  rocks  are  rent  from  time  to  time,  and  heaved  up  or  thrown  down 
several  feet  at  once,  and  disturbed  in  such  a  manner,  that  the  original 
position  of  strata  may,  in  the  course  of  centuries,  be  modified  to  any 
amount. 

It  has  also  been  shown  by  Mr.  Darwin,  that,  in  those  seas  where  cir- 
cular coral  islands  and  barrier  reefs  abound,  there  is  a  slow  and  continued 
sinking  of  the  submarine  mountains  on  which  the  masses  of  coral  are 
based ;  while  there  are  other  areas  of  the  South  Sea,  where  the  land  is 
on  the  rise,  and  where  coral  has  been  upheaved  far  above  the  sea-level. 

It  would  require  a  volume  to  explain  to  the  reader  the  various  facts 
which  establish  the  reality  of  these  movements  of  land,  whether  of  ele- 
vation or  depression,  whether  accompanied  by  earthquakes  or  accom- 
plished slowly  and  without  local  disturbance.  Having  treated  fully  of 
these  subjects  in  the  Principles  of  Geology, J I  shall  assume,  in  the  present 
work,  that  such  changes  are  part  of  the  actual  course  of  nature ;  and 
when  admitted,  they  will  be  found  to  afford  a  key  to  the  interpretation 
of  a  variety  of  geological  appearances,  such  as  the  elevation  of  horizon- 
tal, inclined,  or  disturbed  marine  strata,  and  the  superposition  of  fresh- 

*  In  the  first  three  editions  of  my  Principles  of  Geology,  I  expressed  many 
doubts  as  to  the  validity  of  the  alleged  proofs  of  a  gradual  rise  of  land  in  Sweden ; 
but  after  visiting  that  country,  in  1834,  I  retracted  these  objections,  and  published 
a  detailed  statement  of  the  observations  which  led  me  to  alter  my  opinion  in  the 
Phil.  Trans.  1835,  Part  I.  See  also  the  Principles,  4th  and  subsequent  editions. 

f  See  his  Journal  of  a  Naturalist  in  Voyage  of  the  Beagle,  and  his  work  on 
Coral  Reefs. 

\  See  chapters  xxvii.  to  xxxii.  inclusive,  and  chap.  1. 


CH.  V.J 


INCLINED   STRATIFICATION. 


47 


Fig.  61. 


water  to  marine  deposits,  afterwards  to  be  described.  It  will  also  appear, 
in  the  sequel,  how  much  light  the  doctrine  of  a  continued  subsidence  of 
land  may  throw  on  the  manner  in  which  a  series  of  strata,  formed  in 
shallow  water,  may  have  accumulated  to  a  great  thickness.  The  exca- 
vation of  valleys  also,  and  other  effects  of  denudation,  of  which  I  shall 
presently  treat,  can  alone  be  understood  when  we  duly  appreciate  the 
proofs,  now  on  record,  of  the  prolonged  rising  and  sinking  of  land, 
throughout  wide  areas. 

To  conclude  this  subject,  I  may  remind  the  reader,  that  were  we  to 
embrace  the  doctrine  which  ascribes  the  elevated  position  of  marine 
formations,  and  the  depression  of  certain  freshwater  strata,  to  oscillations 
in  the  level  of  the  waters  instead  of  the  land,  we  should  be  compelled  to 
admit  that  the  ocean  has  been  sometimes  everywhere  much  shallower 
than  at  present,  and  at  others  more  than  three  miles  deeper. 

Inclined  stratification. — The  most  unequivocal  evidence  of  a  change 
in  the  original  position  of  strata  is  afforded  by  their  standing  up  perpen- 
dicularly on  their  edges,  which  is  by  no  means  a  rare  phenomenon,  es- 
pecially in  mountainous  countries.  Thus  we  find  in  Scotland,  on  the 
southern  skirts  of  the  Grampians,  beds  of  pudding-stone  alternating 
with  thin  layers  of  fine  sand,  all  placed  vertically  to  the  horizon.  When 
Saussure  first  observed  certain  conglomer- 
ates in  a  similar  position  in  the  Swiss  Alps, 
he  remarked  that  the  pebbles,  being  for  the 
most  part  of  an  oval  shape,  had  their 
longer  axes  parallel  to  the  planes  of  strati- 
fication (see  fig.  61).  From  this  he  in- 
ferred, that  such  strata  must,  at  first,  have 
been  horizontal,  each  oval  pebble  having 
originally  settled  at  the  bottom  of  the 
water,  with  its  flatter  side  parallel  to  the  horizon,  for  the  same  reason 
that  an  egg  will  not  stand  on  either  end  if  unsupported.  Some  few,  in- 
deed, of  the  rounded  stones  in  a  conglomerate  occasionally  afford  an 
exception  to  the  above  rule,  for  the  same  reason  that  we  see  on  a  shingle 
beach  some  oval  or  flat-sided  pebbles  resting  on  their  ends  or  edges ; 
these  having  been  forced  along  the  bottom  and  against  each  other  by  a 
wave  or  current  so  as  to  settle  in  this  position. 

Vertical  strata,  when  they  can  be  traced  continuously  upwards  or 
downwards  for  some  depth,  are  almost  invariably  seen  to  be  parts  of 
great  curves,  which  may  have  a  diameter  of  a  few  yards,  or  of  several 
miles.  I  shall  first  describe  two  curves  of  considerable  regularity,  which 
occur  in  Forfarshire,  extending  over  a  country  twenty  miles  in  breadth, 
from  the  foot  of  the  Grampians  to  the  sea  near  Arbroath. 

The  mass  of  strata  here  shown  may  be  nearly  2000  feet  in  thickness, 
consisting  of  red  and  white  sandstone,  and  various  colored  shales,  the 
beds  being  distinguishable  into  four  principal  groups,  namely,  No.  l,red 
marl  or  shale ;  No.  2,  red  sandstone,  used  for  building ;  No.  3,  conglom- 
erate ;  and  No.  4,  gray  paving-stone,  and  tile-stone,  with  green  and  red- 


Vertical  conglomerate  and  sandstone. 


CUKVED  STKATA. 


[OH.  V. 


E* 

ll 

«1 


dish  shale,  containing  peculiar  organic  re- 
J  mains.  A  glance  at  the  section  will  show 
'Q  that  each  of  the  formations  2,  3,  4,  are  re- 
«  peated  thrice  at  the  surface,  twice  with  a 
2  southerly,  and  once  with  a  northerly  incli- 
g*  cation  or  dip,  and  the  beds  in  No.  1,  which 
S  are  nearly  horizontal,  are  still  brought  up 
'g  twice  by  a  slight  curvature  to  the  surface, 
•f  once  on  each  side  of  A.  Beginning  at  the 
2"  northwest  extremity,  the  tile-stones  and 
2  conglomerates  No.  4  and  No.  3  are  verti- 
%  cal,  and  they  generally  form  a  ridge  par- 
allel to  the  southern  skirts  of  the  Grampi- 
| »  ans.  The  superior  strata  Nos.  2  and  1  be- 
5 1  come  less  and  less  inclined  on  descending 
g-g  to  the  valley  of  Strathmore,  where  the 
•||  strata,  having  a  concave  bend,  are  said  by 
a-  *  geologists  to  lie  in  a  "  trough"  or  "  basin." 
Through  the  centre  of  this  valley  runs  an 
imaginary  line  A,  called  technically  a 
"synclinal  line,"  where  the  beds,  which 
are  tilted  in  opposite  directions,  may  be 
supposed  to  meet.  It  is  most  important 
for  the  observer  to  mark  such  lines,  for  he 
will  perceive  by  the  diagram,  that  in  trav- 
elling from  the  north  to  the  centre  of  the 
basin,  he  is  always  passing  from  older  to 
newer  beds;  whereas,  after  crossing  the 
line  A,  and  pursuing  his  course  in  the  same 
southerly  direction,  he  is  continually  leav- 
ing the  newer,  and  advancing  upon  older 
strata.  All  the  deposits  which  he  had  be- 
fore examined  begin  then  to  recur  in  re- 
versed order,  until  he  arrives  at  the  central 
axis  of  the  Sidlaw  hills,  where  the  strata 
are  seen  to  form  an  arch  or  saddle,  having 
an  anticlinal  line  B,  in  the  centre.  On  passing  this  line,  and  continuing 
towards  the  S.  E.,  the  formations  4,  3,  and  2,  are  again  repeated,  in  the 
same  relative  order  of  superposition,  but  with  a  southerly  dip.  At  White- 
ness (see  diagram)  it  will  be  seen  that  the  inclined  strata  are  covered  by 
a  newer  deposit,  a,  in  horizontal  beds.  These  are  composed  of  red  conglom- 
erate and  sand,  and  are  newer  than  any  of  the  groups,  1,  2,  3,  4,  before  de- 
scribed, and  rest  unconformaUy  upon  strata  of  the  sandstone  group,  No.  2. 
An  example  of  curved  strata,  in  which  the  bends  or  convolutions  of 
the  rock  are  sharper  and  far  more  numerous  within  an  equal  space,  has 
been  well  described  by  Sir  James  Hall.*  It  occurs  near  St.  Abb's  Head, 
*  Edin.  Trans,  vol.  vii.  pi.  3. 


CH.  V.]  EXPERIMENTS  TO  ILLUSTRATE  CURVED  STRATA. 


49 


on  the  east  coast  of  Scotland,  where  the  rocks  consist  principally  of  a 
bluish  slate,  having  frequently  a  ripple-marked  surface.  The  undulations 
of  the  beds  reach  from  the  top  to  the  bottom  of  cliffs  from  200  to  300 

Fig.  63. 


Curved  strata  of  slate  near  St.  Abb's  Head,  Berwickshire.    (Sir  J.  Hall.) 

feet  in  height,  and  there  are  sixteen  distinct  bendings  in  the  course  of 
about  six  miles,  the  curvatures  being  alternately  concave  and  convex  up- 
wards. 

An  experiment  was  made  by  Sir  James  Hall,  with  a  view  of  illus- 
trating the  manner  in  which  such  strata,  assuming  them  to  have  been 
originally  horizontal,  may  have  been  forced  into  their  present  position.  A 
set  of  layers  of  clay  were  placed  under  a  weight,  and  their  opposite  ends 
pressed  towards  each  other  with  such  force  as  to  cause  them  to  approach 
more  nearly  together.  On  the  removal  of  the  weight,  the  layers  of  clay 
were  found  to  be  curved  and  folded,  so  as  to  bear  a  miniature  resemblance 
to  the  strata  in  the  cliffs.  We  must,  however,  bear  in  mind,  that  in  the 
natural  section  or  sea-cliff  we  only  see  the  foldings  imperfectly,  one  part 
being  invisible  beneath  the  sea,  and  the  other,  or  upper  portion,  being 
supposed  to  have  been  carried  away  by  denudation,  or  that  action  of 

Fig.  64 


water  which  will  be  explained  in  the  next  chapter.  The  dark  lines  m 
the  accompanying  plan  (fig.  64)  represent  what  is  actually  seen  of  the 
strata  in  part  of  the  line  of  cliff  alluded  to  ;  the  fainter  lines,  that  por- 

4 


50  CURVED  STRATA.  [Ca  V. 

tion  which  is  concealed  beneath  the  sea-level,  as  also  that  which  is  sup- 
posed to  have  once  existed  above  the  present  surface. 

We  may  still  more  easily  illustrate  the  effects  which  a  lateral  thrust 
might  produce  on  flexible  strata,  by  placing  several  pieces  of  differently 
colored  cloths  upon  a  table,  and  when  they  are  spread  out  horizontally, 

Fig.  65. 


cover  them  with  a  book.  Then  apply  other  books  to  each  end,  and  force 
them  towards  each  other.  The  folding  of  the  cloths  will  exactly  imitate 
those  of  the  bent  strata.  (See  fig.  65.) 

Whether  the  analogous  flexures  in  stratified  rocks  have  really  been 
due  to  similar  sideway  movements  is  a  question  of  considerable  difficulty. 
It  will  appear  when  the  volcanic  and  granitic  rocks  are  described,  that 
some  of  them  have,  when  melted,  been  injected  forcibly  into  fissures, 
while  others,  already  in  a  solid  state,  have  been  protruded  upwards 
through  the  incumbent  crust  of  the  earth,  by  which  a  great  displace- 
ment of  flexible  strata  must  have  been  caused. 

But  we  also  know  by  the  study  of  regions  liable  to  earthquakes,  that 
there  are  causes  at  work  in  the  interior  of  the  earth  capable  of  producing 
a  sinking  in  of  the  ground,  sometimes  very  local,  but  sometimes  extend- 
ing over  a  wide  area.  The  frequent  repetition,  or  continuance  throughout 
long  periods,  of  such  downward  movements  seems  to  imply  the  formation 
and  renewal  of  cavities  at  a  certain  depth  below  the  surface,  whether  by 
the  removal  of  matter  by  volcanoes  and  hot  springs,  or  by  the  contrac- 
tion of  argillaceous  rocks  by  heat  and  pressure,  or  any  other  combination 
of  circumstances.  Whatever  conjectures  we  may  indulge  respecting  the 
causes,  it  is  certain  that  pliable  beds  may,  in  consequence  of  unequal 
degrees  of  subsidence,  become  folded  to  any  amount,  and  have  all  the 
appearance  of  having  been  compressed  suddenly  by  a  lateral  thrust. 

The  "  Creeps,"  as  they  are  called  in  coal-mines,  afford  an  excellent  il 
lustration  of  this  fact.— First,  it  may  be  stated  generally,  that  the  exca 
vation  of  coal  at  a  considerable  depth  causes  the  mass  of  overlying  strata 
to  sink  down  bodily,  even  when  props  are  left  to  support  the  roof  of  the 
mine.  "In  Yorkshire,"  says  Mr.  Buddie,  "three  distinct  subsidences 
were  perceptible  at  the  surface,  after  the  clearing  out  of  three  seams  of 
coal  below,  and  innumerable  vertical  cracks  were  caused  in  the  incum- 
bent mass  of  sandstone  and  shale,  which  thus  settled  down."*  The  ex- 

*  Proceedings  of  Geol.  Soc.  vol.  iii.  p.  148. 


CH.  V.I 


CREEPS   IX   COAL-MIXES. 


51 


act  amount  of  depression  in  these  cases  can  only  be  accurately  measured 
where  water  accumulates  on  the  surface,  or  a  railway  traverses  a  coal-field. 
When  a  bed  of  coal  is  worked  out,  pillars  or  rectangular  masses  of 
coal  are  left  at  intervals  as  props  to  support  the  roof  and  protect  the 
colliers.  Thus  in  fig.  66,  representing  a  section  at  Wallsend,  Newcastle, 


the  galleries  which  have  been  excavated  are  represented  by  the  white 
spaces  a  6,  while  the  adjoining  dark  portions  are  parts  of  the  original 
coal-seam  left  as  props,  beds  of  sandy  clay  or  shale  constituting  the  floor 
of  the  mine.  When  the  props  have  been  reduced  in  size,  they  are  pressed 


52  CURVED  STRATA,  [Ce.  Y 

down  by  the  weight  of  overlying  rocks  (no  less  than  630  feet  thick) 
upon  the  shale  below,  which  is  thereby  squeezed  and  forced  up  into  the 
open  spaces. 

Now  it  might  have  been  expected,  that  instead  of  the  floor  rising  up, 
the  ceiling  would  sink  down,  and  this  effect,  called  a  "  Thrust,"  does,  in 
fact,  take  place  where  the  pavement  is  more  solid  than  the  roof.  But  it 
usually  happens,  in  coal-mines,  that  the  roof  is  composed  of  hard  shale, 
or  occasionally  of  sandstone,  more  unyielding  than  the  foundation,  which 
often  consists  of  clay.  Even  where  the  argillaceous  substrata  are  hard 
at  first,  they  soon  become  softened  and  reduced  to  a  plastic  state  when 
exposed  to  the  contact  of  air  and  water  in  the  floor  of  a  mine. 

The  first  symptom  of  a  "  creep,"  says  Mr.  Buddie,  is  a  slight  curvature 
at  the  bottom  of  each  gallery,  as  at  a,  fig.  66  ;  then  the  pavement  con- 
tinuing to  rise,  begins  to  open  with  a  longitudinal  crack,  as  at  b :  then 
the  points  of  the  fractured  ridge  reach  the  roof,  as  at  c  ;  and,  lastly,  the 
upraised  beds  close  up  the  whole  gallery,  and  the  broken  portions  of  the 
ridge  are  reunited  and  flattened  at  the  top,  exhibiting  the  flexure  seen  at 
d.  Meanwhile  the  coal  in  the  props  has  become  crushed  and  cracked  by 
pressure.  It  is  also  found,  that  below  the  creeps  a,  6,  c,  d,  an  inferior 
stratum,  called  the  "  metal  coal,"  which  is  3  feet  thick,  has  been  fractured 
at  the  points  e,  /,  #,  h,  and  has  risen,  so  as  to  prove  that  the  upward 
movement,  caused  by  the  working  out  of  the  "main  coal,"  has  been 
propagated  through  a  thickness  of  54  feet  of  argillaceous  beds,  whieh 
intervene  between  the  two  coal  seams.  This  same  displacement  has  also 
been  traced  downwards  more  than  150  feet  below  the  metal  coal,  but  it 
grows  continually  less  and  less  until  it  becomes  imperceptible. 

No  part  of  the  process  above  described  is  more  deserving  of  our  no- 
tice than  the  slowness  with  which  the  change  in  the  arrangement  of  the 
beds  is  brought  about.  Days,  months,  or  even  years,  will  sometimes 
elapse  between  the  first  bending  of  the  pavement  and  the  time  of  its 
reaching  the  roof.  Where  the  movement  has  been  most  rapid,  the  curv- 
ature of  the  beds  is  most  regular,  and  the  reunion  of  the  fractured  ends 
most  complete ;  whereas  the  signs  of  displacement  or  violence  are  great- 
est in  those  creeps  which  have  required  months  or  years  for  their  entire 
accomplishment.  Hence  we  may  conclude  that  similar  changes  may 
have  been  wrought  on  a  larger  scale  in  the  earth's  crust  by  partial  and 
gradual  subsidences,  especially  where  the  ground  has  been  undermined 
throughout  long  periods  of  time  ;  and  we  must  be  on  our  guard  against 
inferring  sudden  violence,  simply  because  the  distortion  of  the  beds  is 
excessive. 

Between  the  layers  of  shale,  accompanying  coal,  we  sometimes  see 
the  leaves  of  fossil  ferns  spread  out  as  regularly  as  dried  plants  between 
sheets  of  paper  in  the  herbarium  of  a  botanist.  These  fern-leaves,  or 
fronds,  must  have  rested  horizontally  on  soft  mud,  when  first  deposited. 
If,  therefore,  they  and  the  layers  of  shale  are  now  inclined,  or  standing 
on  end,  it  is  obviously  the  effect  of  subsequent  derangement.  The  proof 
becomes,  if  possible,  still  more  striking  when  these  strata,,  including 


OH.  V.]  DIP   AND   STRIKE.  53 

vegetable  remains,  are  curved  again  and  again,  and  even  folded  into  the 
form  of  the  letter  Z,  so  that  the  same  continuous  layer  of  coal  is  cut 
through  several  times  in  the  same  perpendicular  shaft.  Thus,  in  the 
coal-field  near  Mons,  in  Belgium,  these  zigzag  bendings  are  repeated  four 

Fig.  67. 


Zigzag  flexures  of  coal  near  Mons. 

or  five  times,  in  the  manner  represented  in  fig.  67,  the  black  lines  repre- 
senting seams  of  coal.* 

Dip  and  strike. — In  the  above  remarks,  several  technical  terms  have 
been  used,  such  as  dip,  the  unconformable  position  of  strata,-  and  the 
anticlinal  and  synclinal  lines,  which,  as  well  as  the  strike  of  the  beds,  I 
shall  now  explain.  If  a  stratum  or  bed  of  rock,  instead  of  being  quite 
level,  be  inclined  to  one  side,  it  is  said  to  dip  ;  the  point  of  the  compass 
to  which  it  is  inclined  is  called  the  point  of  dip,  and  the  degree  of  devi- 
ation from  a  level  or  horizontal  line  is  called  the  amount  of  dip,  or  the 
Fig.  63.  angle  of  dip.  Thus,  in  the  annexed 

diagram  (fig.  68),  a  series  of  strata 
are  inclined,  and  they  dip  to  the  north 
at  an  angle  of  forty-five  degrees.  The 
strike,  or  line  of  bearing,  is  the  pro- 
longation or  extension  of  the  strata 
in  a  direction  at  right  angles  to  the  dip ;  and  hence  it  is  sometimes  called 
the  direction  of  the  strata.  Thus,  in  the  above  instance  of  strata  dipping 
to  the  north,  their  strike  must  necessarily  be  east  and  west.  We  have 
borrowed  the  word  from  the  German  geologists,  streichen  signifying  to 
extend,  to  have  a  certain  direction.  Dip  and  strike  may  be  aptly  illus- 
trated by  a  row  of  houses  running  east  and  west,  the  long  ridge  of 
the  roof  representing  the  strike  of  the  stratum  of  slates,  which  dip  on 
one  side  to  the  north,  and  on  the  other  to  the  south. 

A  stratum  which  is  horizontal,  or  quite  level  in  all  directions,  has 
neither  dip  nor  strike. 

It  is  always  important  for  the  geologist,  who  is  endeavoring  to  com- 
prehend the  structure  of  a  country,  to  learn  how  the  beds  dip  in  every 
part  of  the  district ;  but  it  requires  some  practice  to  avoid  being  occa- 
sionally deceived,  both  as  to  the  point  of  dip  and  the  amount  of  it. 

*  See  plan  by  M.  Chevalier,  Burat's  D'Aubuisson,  torn,  il  p.  334. 


54  DIP  AND  STKIKE.  [Cu.  7. 

If  the  upper  surface  of  a  hard  stony  stratum  be  uncovered,  whether 
artificially  in  a  quarry,  or  by  the  waves  at  the  foot  of  a  cliff,  it  is  easy 
to  determine  towards  what  point  of  the  compass  the  slope  is  steepest,  or 
in  what  direction  water  would  flow,  if  poured  upon  it.  This  is  the  true 
dip.  But  the  edges  of  highly  inclined  strata  may  give  rise  to  perfectly 
horizontal  lines  in  the  face  of  a  vertical  cliff,  if  the  observer  see  the 
strata  in  the  line  of  their  strike,  the  dip  being  inwards  from  the  face  of 
the  cliff.  If,  however,  we  come  to  a  break  in  the  cliff,  which  exhibits  a 
section  exactly  at  right  angles  to  the  line  of  the  strike,  we  are  then  able 
to  ascertain  the  true  dip.  In  the  annexed  drawing  (fig.  69),  we  may 
suppose  a  headland,  one  side  of  which  faces  to  the  north,  where  the 

Fig.  69. 


Apparent  horizontally  of  inclined  strata. 

beds  would  appear  perfectly  horizontal  to  a  person  in  the  boat ;  while  in 
the  other  side  facing  the  west,  the  true  dip  would  be  seen  by  the  person 
on  shore  to  be  at  an  angle  of  40°.  If,  therefore,  our  observations  are 
confined  to  a  vertical  precipice  facing  in  one  direction,  we  must  endeavor 
to  find  a  ledge  or  portion  of  the  plane  of  one  of  the  beds  projecting  be- 
yond the  others,  in  order  to  ascertain  the  true  dip. 

It  is  rarely  important  to  determine  the  angle  of  inclination  with  such 
minuteness  as  to  require  the  aid  of  the  instrument  called  a  clinometer. 
We  may  measure  the  angle  within  a  few  degrees  by  standing  exactly 
Fig.  70.  opposite  to  a  cliff  where  the  true  dip  is 

exhibited,  holding  the  hands  immediately 
before  the  eyes,  and  placing  the  fingers  of 
one  in  a  perpendicular,  and  of  the  other  in 
a  horizontal  position,  as  in  fig.  70.  It  is 
thus  easy  to  discover  whether  the  lines  of 
the  inclined  beds  bisect  the  angle  of  90°, 
formed  by  the  meeting  of  the  hands,  so  as 
to  give  an  angle  of  45°,  or  whether  it 
would  divide  the  space  into  two  equal  or 
unequal  portions.  The  upper  dotted  line 
may  express  a  stratum  dipping  to  the  north ;  but  should  the  beds  dip 
precisely  to  the  opposite  point  of  the  compass  as  in  the  lower  dotted 


CH.  V.] 


DIP   AND    STEIKE. 


55 


line,  it  will  be  seen  that  the  amount  of  inclination  may  still  be  measured 
by  the  hands  with  equal  facility. 

It  has  been  already  seen,  in  describing  the  curved  strata  on  the  east 
coast  of  Scotland,  in  Forfarshire  and  Berwickshire,  that  a  series  of  con- 
cave and  convex  bendings  are  occasionally  repeated  several  times.  These 
usually  form  part  of  a  series  of  parallel  waves  of  strata,  which  are  pro- 
longed in  the  same  direction  throughout  a  considerable  extent  of  country. 
Thus,  for  example,  in  the  Swiss  Jura,  that  lofty  chain  of  mountains  has 
been  proved  to  consist  of  many  parallel  ridges,  with  intervening  longi- 
tudinal valleys,  as  in  fig.  71,  the  ridges  being  formed  by  curved  fossilif- 
erous  strata,  of  which  the  nature  and  dip  are  occasionally  displayed  in 
deep  transverse  gorges,  called  "  cluses,"  caused  by  fractures  at  right  angles 
to  the  direction  of  the  chain.*  Now  let  us  suppose  these  ridges  and 
parallel  valleys  to  run  north  and  south,  we  should  then  say  that  the 
strike  of  the  beds  is  north  and  south,  and  the  dip  east  and  west  Lines 
drawn  along  the  summits  of  the  ridges,  A,  B,  would  be  anticlinal  lines, 
and  one  following  the  bottom  of  the  adjoining  valleys  a  synclinal  line. 

Fig.7t 


Fig.  7-2. 


Fig.  73. 


Section  illustrating  the  structure  of  the  Svriss  Jura. 

It  will  be  observed  that  some  of  these  ridges,  A,  B,  are  unbroken  on  the 
summit,  whereas  one  of  them,  C,  has  been  fractured  along  the  line  of 
strike,  and  a  portio  i  of  it  carried  away  by  denudation,  so  that  the  ridges 
of  the  beds  in  the  formations  a,  6,  c,  come  out  to  the  day,  or,  as  the 

miners  say,  crop  out,  on  the  sides 
of  a  valley.     The  ground  plan  of 
§  such  a  denuded  ridge  as  C,  as  given 
I  in  a  geological  map,  may  be  ex- 
|  pressed  by  the  diagram  fig.  72,  and 
|  the  cross  section  of  the  same  by 
|  fig.  73.    The  line  D  E,  fig.  72,  is 
the  anticlinal  line,  on  each  side  of 
which  the  dip  is  in  opposite  direc- 


Ground  plan  of  the  denuded  ridg*C,  fig.  71. 


*  Seo  M.  Thurmann's  work,  "  Essai  sur  les  Soulevemena  Jurassiques  du  Por- 
rentruy,  Paris,  18S2,"  with  whom  I  examined  part  of  these  mountains  in  1835. 


56 


OUTCROP   OF   STRATA. 


[On.  V. 


tions,  as  expressed  by  the  arrows.     The  emergence  of  strata  at  the  sur- 
face is  called  by  miners  their  outcrop  or  basset. 

If,  instead  of  being  folded  into  parallel  ridges,  the  beds  form  a  boss 
or  dome-shaped  protuberance,  and  if  we  suppose  the  summit  of  the 
dome  carried  off,  the  ground  plan  would  exhibit  the  edges  of  the  strata 
forming  a  succession  of  circles,  or  ellipses,  round  a  common  centre. 
These  circles  are  the  lines  of  strike,  and  the  dip  being  always  at  right 
angles  is  inclined  in  the  course  of  the  circuit  to  every  point  of  the  com- 
pass, constituting  what  is  termed  a  qua-quaversal  dip — that  is,  turning 
each  way. 

There  are  endless  variations  in  the  figures  described  by  the  basset- 
edges  of  the  strata,  according  to  the  different  inclination  of  the  beds, 
and  the  mode  in  which  they  happen  to  have  been  denuded.  One 
of  the  simplest  rules  with  which  every  geologist  should  be  acquainted, 
relates  to  the  V-like  form  of  the  beds  as  they  crop  out  in  an  ordinary 
valley.  First,  if  the  strata  be  horizontal,  the  V-likc  form  will  be 
also  on  a  level,  and  the  newest  strata  will  appear  at  the  greatest 
heights. 

Secondly,  if  the  beds  be  inclined  and  intersected  by  a  valley  sloping 
in  the  same  direction,  and  the  dip  of  the  beds  be  less  steep  than  the 
slope  of  the  valley,  then  the  V's,  as  they  are  often  termed  by  miners, 
will  point  upwards  (see  fig.  74),  those  formed  by  the  newer  beds  appear- 
ing in  a  superior  position, 
and  extending  highest  up 
the  valley,  as  A  is  seen 
above  B. 

Thirdly,  if  the  dip  of  the 
beds  be  steeper  than  the 
slope  of  the  valley,  then 
the  V's  will  point  down- 
wards (see  fig.  75),  and 
those  formed  of  the  older 
beds  will  now  appear  up- 
permost, as  B  appears  above 
A. 

Fourthly,  in  every  case 
where  the  strata  dip  in  a 
contrary  direction  to  the 
slope  of  the  valley,  what- 
ever be  the  angle  of  incli- 
nation, the  newer  beds  will 
appear  the  highest,  as  in 
the  first  and  second  cases. 
This  is  shown  by  the  draw- 
ing (fig.  76),  which  exhib- 
its strata  rising  at  an  angle 

Slope  of  valley  20°,  dip  of  strata  50°.  of    20°,      and      crossed      by 


Fig.  74. 


Slope  of  valley  40°,  dip  of  strata  20°. 
Fig.  75. 


CH.  V.I 


AXT1CLIXAL   AND   SYXCLIXAL   LIXES. 


57 


Slope  of  valley  20°,  dip  of  strata  20°,  in  opposite 
directions. 


a  valley,  which  declines  in  an 
opposite  direction  at  20°.* 

These  rules  may  often  be  of 
great  practical  utility;  for 
the  different  degrees  of  dip 
occurring  in  the  two  cases 
represented  in  figures  74  and 
7  5,  may  occasionally  be  en- 
countered in  following  the 
same  line  of  flexure  at  points 
a  few  miles  distant  from 
each  other.  A  miner  un- 
acquainted with  the  rule, 
who  had  first  explored  the  valley  (fig.  74),  may  have  sunk  a  vertical 
shaft  below  the  coal-seam  A,  until  he  reached  the  inferior  bed  B.  He 
might  then  pass  to  the  valley  fig.  7o,  and  discovering  there  also  the  out- 
crop of  two  coal-seams,  might  begin  his  workings  in  the  uppermost  in  the 
expectation  of  coming  down  to  the  other  bed  A,  which  would  be  observed 
cropping  out  lower  down  the  valley.  But  a  glance  at  the  section  will 
demonstrate  the  futility  of  such  hopes. 

In  the  majority  of  cases,  an  anticlinal  axis  forms  a  ridge,  and  a  syn- 
clinal axis  a  valley,  as  in  A,  B,  fig.  62,  p.  48 ;  but  there  are  exceptions 
to  this  rule,  the  beds  sometimes  sloping  in- 
wards from  either  side  of  a  mountain,  as  in 
fig.  77. 

On  following  one  of  the  anticlinal  ridges 
of  the  Jura,  before  mentioned,  A,  B,  C,  fig. 
71,  we  often  discover  longitudinal  cracks  and 
sometimes  large  fissures  along  the  line  where 
the  flexure  was  greatest.  Some  of  these,  as  above  stated,  have  been  en- 
larged by  denudation  into  valleys  of  considerable  width,  as  at  C,  fig.  71, 
which  follow  the  line  of  strike,  and  which  we  may  suppose  to  have  been 
hollowed  out  at  the  time  when  these  rocks  were  still  beneath  the  level  of 
the  sea,  or  perhaps  at  the  period  of  their  gradual  emergence  from  be- 
neath the  waters.  The  existence  of  such  cracks  at  the  point  of  the 
sharpest  bending  of  solid  strata  of  limestone  is  precisely  what  we  should 
have  expected ;  but  the  occasional  want  of  all  similar  signs  of  fracture, 
even  where  the  strain  has  been  greatest,  as  at  a,  fig.  71,  is  not  always 
easy  to  explain.  "We  must  imagine  that  many  strata  of  limestone,  chert, 
and  other  rocks  which  are  now  brittle,  were  pliant  when  bent  into  their 
present  position.  They  may  have  owed  their  flexibility  in  part  to  the 

*  I  am  indebted  to  the  kindness  of  T.  Sopwith,  Esq.,  for  three  models  which  I 
have  copied  in  the  above  diagrams ;  but  the  beginner  may  find  it  by  no  means 
easy  to  understand  such  copies,  although,  if  he  were  to  examine  and  handle  the 
originals,  turning  them  about  in  different  ways,  he  -would  at  once  comprehend 
their  meaning,  as  well  as  the  import  of  others  far  more  complicated,  \vhich  the 
same  engineer  has  constructed  to  illustrate  faults. 


Fig.  T7. 


58 


REVERSED  DIP  OF  STRATA. 


[On. 


fluid  matter  which  they  contained  in  their  minute  pores,  as  before 
described  (p.  35),  and  in  part  to  the  permeation  of  sea-water  while  they 
were  yet  submerged. 

At  the  western  extremity  of  the  Pyrenees,  great  curvatures  of  the 
strata  are  seen  in  the  sea  cliffs,  where  the  rocks  consist  of  marl,  grit,  and 
che-t.  At  certain  points,  as  at  a,  fig.  78,  some  of  the  bendings  of  the 


Fig.  78. 


Fig.  79. 


Strata  of  chert,  grit,  and  marl,  near  St.  Jean  de  Luz. 

flinty  chert  are  so  sharp,  that  specimens  might  be  broken  off,  well  fitted 
to  serve  as  ridge-tiles  on  the  roof  of  a  house.  Although  this  chert 
could  not  have  been  brittle  as  now,  when  first  folded  into  this  shape,  it 
presents,  nevertheless,  here  and  there  at  the  points  of  greatest  flexure 
small  cracks,  which  show  that  it  was  solid,  and  not  wholly  incapable  of 
breaking  at  the  period  of  its  displacement.  The  numerous  rents  alluded 
to  are  not  empty,  but  filled  with  chalcedony  and  quartz. 

Between  San  Caterina  and  Castrogiovanni,  in  Sicily,  bent  and  undu- 
lating gypseous  marls  occur,  with  here  and  there  thin  beds  of  solid 

gypsum  interstratified.  Sometimes  these 
solid  layers  have  been  broken  into  detached 
fragments,  still  preserving  their  sharp  edges 
(ff  9i  %•  *79),  while  the  continuity  of  the 
more  pliable  and  ductile  marls,  m  m,  has 
not  been  interrupted. 

I  shall  conclude  my  remarks  on  bent 
strata  by  stating,  that,  in  mountainous  re- 
gions like  the  Alps,  it  is  often  difficult  for 
an  experienced  geologist  to  determine  correctly  the  relative  age  of  beds 
by  superposition,  so  often  have  the  strata  been  folded  back  upon  them- 
selves, the  upper  parts  of  the  curve  having  been  removed  by  denudation. 
Thus,  if  we  met  with  the  strata  seen  in  the  section  fig.  80,  we  should 

naturally  suppose  that  there  were  twelve 
distinct  beds,  or  sets  of  beds,  No.  1  being 
the  newest,  and  No.  12  the  oldest  of  the 

_  series.     But  this  section  may,  perhaps, 

exhibit  merely  six  beds,  which  have  been 

folded  in  the  manner  seen  in  fig.  81,  so  that  each  of  them  is  twice  re- 
peated, the  position  of  one-half  being  reversed,  and  part  of  No.  1,  origi- 
nally the  uppermost,  having  now  become  the  lowest  of  the  series.  These 
phenomena  are  often  observable  on  a  magnificent  scale  in  certain  regions 
in  Switzerland  in  precipices  from  2000  to  3000  feet  in  perpendicular 
height.  In  the  Iselten  Alp,  in  the  valley  of  the  Lutschine,  between 


j.  gypsum.       m.  marl. 


Fig.  80. 


CH.  V.] 


CURVED   STRATA  IN  THE   ALPS. 
Fig.  8L 


L\\\\\\\\\\\\ 


59 


Unterseen  and  Grindelwald,  curves  of  calcareous  shale  are  seen  from 
1000  to  1500  feet  in  height,  in  which  the  beds  sometimes  plunge  down 
vertically  for  a  depth  of  1000  feet  and  more,  before  they  bend  round 

Fig.  82. 


Curved  strata  of  the  Iselten  Alp. 

again.     There  are  many  flexures  not  inferior  in  dimensions  in  the  Pyre- 
nees, as  those  near  Gavarnie,  at  the  base  of  Mount  Perdu. 

Unconformable  stratification. — Strata  are  said  to  be  unconformable, 
when  one  series  is  so  placed  over  another,  that  the  planes  of  the  superior 
repose  on  the  edges  of  the  inferior  (see  fig.  83).  In  this  case  it  is  evi- 

Fig.  83. 


Unconformable  junction  of  old  red  sandstone  and  Silurian  schist  at  the  Siccar  Point,  near  St  Abb's 
Head,  Berwickshire.    See  also  Frontispiece. 

dent  that  a  period  had  elapsed  between  the  production  of  the  two  sets 
of  strata,  and  that,  during  this  interval,  the  older  series  had  been  tilted 


60  UNCONFOKMABLE   STRATIFICATION.  [On.  V 

and  disturbed.  Afterwards  the  upper  series  was  thrown  down  in  hori- 
zontal strata  upon  it.  If  these  superior  beds,  as  d,  d,  fig.  83,  are  also 
inclined,  it  is  plain  that  the  lower  strata,  a,  a,  have  been  twice  displaced ; 
first,  before  the  deposition  of  the  newer  beds,  c?,  <#,  and  a  second  time 
when  these  same  strata  were  thrown  out  of  the  horizontal  position. 

Playfair  has  remarked*  that  this  kind  of  junction,  which  we  now  call 
unconformable,  had  been  described  before  the  time  of  Hutton,  but  that 
he  was  the  first  geologist  who  appreciated  its  importance,  as  illustrating 
the  high  antiquity  and  great  revolutions  of  the  globe.  He  had  observed 
that  where  such  contacts  occur,  the  lowest  beds  of  the  newer  series  very 
generally  consist  of  a  breccia  or  conglomerate  consisting  of  angular  and 
rounded  fragments,  derived  from  the  breaking  up  of  the  more  ancient 
rocks.  On  one  occasion  the  Scotch  geologist  took  his  two  distinguished 
pupils,  Playfair  and  Sir  James  Hall,  to  the  cliffs  on  the  east  coast  of 
Scotland,  near  the  village  of  Eyemouth,  not  far  from  St.  Abb's  Head, 
where  the  schists  of  the  Lammermuir  range  are  undermined  and  dis- 
sected by  the  sea.  Here  the  curved  and  vertical  strata,  now  known  to 
be  of  Silurian  age,  and  which  often  exhibit  a  ripple-marked  surface,  are 
well  exposed  at  the  headland  called  the  Siccar  Point,  penetrating  with 
their  edges  into  the  incumbent  beds  of  slightly  inclined  sandstone,  in 
which  large  pieces  of  the  schist,  some  round  and  others  angular,  are 
united  by  an  arenaceous  cement.  "  What  clearer  evidence,"  exclaims 
Playfair,  "  could  we  have  had  of  the  different  formation  of  these  rocks, 
and  of  the  long  interval  which  separated  their  formation,  had  we  actually 
seen  them  emerging  from  the  bosom  of  the  deep  ?  We  felt  ourselves 
necessarily  carried  back  to  the  time  when  the  schistus  on  which  we  stood 
was  yet  at  the  bottom  of  the  sea,  and  when  the  sandstone  before  us  was 
only  beginning  to  be  deposited  in  the  shape  of  sand  or  mud,  from  the 
waters  of  a  superincumbent  ocean.  An  epoch  still  more  remote  pre- 
sented itself,  when  even  the  most  ancient  of  these  rocks,  instead  of 
standing  upright  in  vertical  beds,  lay  in  horizontal  planes  at  the  bottom 
of  the  sea,  and  was  not  yet  disturbed  by  that  immeasurable  force  which 
has  burst  asunder  the  solid  pavement  of  the  globe.  Revolutions  still 
more  remote  appeared  in  the  distance  of  this  extraordinary  perspective. 
The  mind  seemed  to  grow  giddy  by  looking  so  far  into  the  abyss  of 
time ;  and  while  we  listanod  with  earnestness  and  admiration  to  the 
philosopher  who  was  now  unfolding  to  us  the  order  and  series  of  these 
wonderful  events,  we  became  sensible  how  much  farther  reason  may 
sometimes  go  than  imagination  can  venture  to  follow."f 

In  the  frontispiece  of  this  volume  the  reader  will  see  a  view  of  this 
classical  spot,  reduced  from  a  large  picture,  faithfully  drawn  and  colored 
from  nature  by  the  youngest  son  of  the  late  Sir  James  Hall.  It  was  im- 
possible, however,  to  do  justice  to  the  original  sketch,  in  an  engraving,  as 
the  contrast  of  the  red  sandstone  and  the  light  fawn-colored  vertical  schists 

*  Biographical  account  of  Dr.  Hutton. 

f  Playfair,  ibid. ;  see  his  Works,  Edin.  1822,  vol.  iv.  p.  81. 


CH,  V.] 


FISSURES  IN  STRATA. 


61 


could  not  be  expressed.  From  the  point  of  view  here  selected,  the  under- 
lying beds  of  the  perpendicular  schist,  a,  are  visible  at  b  through  a  small 
opening  in  the  fractured  beds  of  the  covering  of  red  sandstone,  d  d,  while 
on  the  vertical  face  of  the  old  schist  at  a'  a"  a  conspicuous  ripple-mark 
is  displayed. 

It  often  happens  that  in  the  interval  between  the  deposition  of  two  sets 
of  unconformable  strata,  the  inferior  rock  has  not  only  been  denuded,  but 
drilled  by  perforating  shells.  Thus,  for  example,  at  Autreppe  and  Gusigny, 
near  MODS,  beds  of  an  ancient  (primary  or  paleozoic)  limestone,  highly 

Fig.  84 


Junction  of  unconformable  strata  near  Mons,  in  Belgium. 


inclined,  and  often  bent,  are  covered  with  horizontal  strata  of  greenish 
and  whitish  marls  of  the  Cretaceous  formation.  The  lowest  and  there- 
fore the  oldest  bed  of  the  horizontal  series  is  usually  the  sand  and  con- 
glomerate, a,  in  which  are  rounded  fragments  of  stone,  from  an  inch  to 
two  feet  in  diameter.  These  fragments  have  often  adhering  shells  at- 
tached to  them,  and  have  been  bored  by  perforating  mollusca.  The 
solid  surface  of  the  inferior  limestone  has  also  been  bored,  so  as  to  ex- 
hibit cylindrical  and  pear-shaped  cavities,  as  at  c,  the  work  of  saxicavous 
mollusca  ;  and  many  rents,  as  at  6,  which  descend  several  feet  or  yards 
into  the  limestone,  have  been  filled  with  sand  and  shells,  similar  to  those 
in  the  stratum  a. 

Fractures  of  the  strata  and  faults. — Numerous  rents  may  often  be 
seen  in  rocks  which  appear  to  have  been  simply  broken,  the  separated 
parts  remaining  in  the  same  places  ;  but  we  often  find  a  fissure,  several 
inches  or  yards  wide,  intervening  between  the  disunited  portions.  These 
fissures  are  usually  filled  with  fine  earth  and  sand,  or  with  angular  frag- 
ments of  stone,  evidently  derived  from  the  fracture  of  the  contiguous 
rocks. 

It  is  not  uncommon  to  find  the  mass  of  rock,  on  one  side  of  a  fissure, 
thrown  up  above  or  down  below  the  mass  with  which  it  was  once  in 
contact  on  the  other  side.  This  mode  of  displacement  is  called  a  shift, 
slip,  or  fault.  "  The  miner,"  says  Playfair,  describing  a  fault,  "  is  often 
perplexed,  in  his  subterraneous  journey,  by  a  derangement  in  the  strata, 
which  changes  at  once  all  those  lines  and  bearings  which  had  hitherto 
directed  his  course.  When  his  mine  reaches  a  certain  plane,  which  is 
sometimes  perpendicular,  as  in  A  B,  fig.  85,  sometimes  oblique  to  the 
horizon  (as  in  C  D,  ibid.),  he  finds  the  beds  of  rock  broken  asunder, 
those  on  the  one  side  of  the  plane  having  changed  their  place,  by  sliding 
in  a  particular  direction  along  the  face  of  the  others.  In  this  motion 
they  have  sometimes  preserved  their  parallelism,  as  in  fig.  85,  so  that 


62 


FAULTS. 
Fig.  85. 


[Oa  V 


TJ  D 

Faults.    A  B  perpendicular,  C  D  oblique  to  the  horizon. 

the  strata  on  each  side  of  the  faults  A  B,  CD,  continue  parallel  to  one 
another ;  in  other  cases,  the  strata  on  each  side  are  inclined,  as  in  a,  6,  c,  d 

Fig.  86. 


p  d        c     f,    a 

E  F,  fault  or  fissure  filled  with  rubbish,  on  each  side  of  which  the  shifted 
strata  are  not  parallel. 

(fig.  86),  though  their  identity  is  still  to  be  recognized  by  their  possessing 
the  same  thickness,  and  the  same  internal  characters."* 

In  Coalbrook  Dale,  says  Mr.  Prestwich,f  deposits  of  sandstone,  shale, 
and  coal,  several  thousand  feet  thick,  and  occupying  an  area  of  many 
miles,  have  been  shivered  into  fragments,  and  the  broken  remnants  have 
been  placed  in  very  discordant  positions,  often  at  levels  differing  several 
hundred  feet  from  each  other.  The  sides  of  the  faults,  when  perpendicu- 
lar, are  commonly  separated  several  yards,  but  are  sometimes  as  much 
as  50  yards  asunder,  the  interval  being  filled  with  broken  debris  of  the 
strata.  In  following  the  course  of  the  same  fault,  it  is  sometimes  found 
to  produce  in  different  places  very  unequal  changes  of  level,  the  amount 
of  shift  being  in  one  place  300,  and  in  another  700  feet,  which  arises,  in 
some  cases,  from  ;he  union  of  two  or  more  faults.  In  other  words,  the 
disjointed  strata  have  in  certain  districts  been  subjected  to  renewed  move- 
ments, which  they  have  not  suffered  elsewhere. 

We  may  occasionally  see  exact  counterparts  of  these  slips,  on  a  small 
scale,  in  pits  of  loose  sand  and  gravel,  many  of  which  have  doubtless 
been  caused  by  the  drying  and  shrinking  of  argillaceous  and  other  beds? 
slight  subsidences  having  taken  place  from  failure  of  support.  Sometimes, 
however,  even  these  small  slips  may  have  been  produced  during  earth- 
quakes ;  for  land  has  been  moved,  and  its  level,  relatively  to  the  sea, 
considerably  altered,  within  the  period  when  much  of  the  alluvial  sand 
and  gravel  now  covering  the  surface  of  continents  was  deposited. 

*  Playfair,  Illust.  of  Hutt.  Theory,  §  42. 
f  Geol.  Trans,  second  series,  vol.  v.  p.  452. 


CH.  V.] 


FAULTS. 


63 


I  have  already  stated  that  a  geologist  must  be  on  his  guard,  in  a  region 
of  disturbed  strata,  against  inferring  repeated  alternations  of  rocks,  when, 
in  fact,  the  same  strata,  once  continuous,  have  been  bent  round  so  as  to 
recur  in  the  same  section,  and  with  the  same  dip.  A  similar  mistake  has 
often  been  occasioned  by  a  series  of  faults. 

If,  for  example,  the  dark  line  A  H  (fig.  8Y)  represent  the  surface  of  a 
country  on  which  the  strata  a  b  c  frequently  crop  out,  an  observer,  who 

Fig.  87. 


Apparent  alternations  of  strata  caused  by  vertical  faults. 

is  proceeding  from  H  to  A,  might  at  first  imagine  that  at  every  step  he 
was  approaching  new  strata,  whereas  the  repetition  of  the  same  beds  has 
been  caused  by  vertical  faults,  or  downthrows.  Thus,  suppose  the  origi- 
nal mass,  A,  B,  C,  D,  to  have  been  a  set  of  uniformly  inclined  strata,  and 
that  the  different  masses  under  E  F,  F  G,  and  G  D,  sank  down  success- 
ively, so  as  to  leave  vacant  the  spaces  marked  in  the  diagram  by  dotted 
lines,  and  to  occupy  those  marked  by  the  continuous  lines ;  then  let  de- 
nudation take  place  along  the  line  A  H,  so  that  the  protruding  masses 
indicated  by  the  fainter  lines  are  swept  away, — a  miner,  who  has  not  dis- 
covered the  faults,  finding  the  mass  a,  which  we  will  suppose  to  be  a  bed 
of  coal  four  times  repeated,  might  hope  to  find  four  beds,  workable  to  an 
indefinite  depth,  but  first  on  arriving  at  the  fault  G  he  is  stopped  sud- 
denly in  his  workings,  upon  reaching  the-  strata  of  sandstone  c,  or  on  ar- 
riving at  the  line  of  fault  F,  he  comes  partly  upon  the  shale  &,  and  partly 
on  the  sandstone  c,  and  on  reaching  E  he  is  again  stopped  by  a  wall  com- 
posed of  the  rock  d. 

The  very  different  levels  at  which  the  separated  parts  of  the  same  strata 
are  found  on  the  different  sides  of  the  fissure,  in  some  faults,  is  truly 
astonishing.  One  of  the  most  celebrated  in  England  is  that  called  the 
"  ninety-fathom  dike,"  in  the  coal-field  of  Newcastle.  This  name  has 
been  given  to  it,  because  the  same  beds  are  ninety  fathoms  lower  on  the 
northern  than  they  are  on  the  southern  side.  The  fissure  has  been  filled 
by  a  body  of  sand,  which  is  now  in  the  state  of  sandstone,  and  is  called 
the  dike,  which  is  sometimes  very  narrow,  but  in  other  places  more  than 
twenty  yards  wide.*  The  walls  of  the  fissure  are  scored  by  grooves,  such 

*  Conybeare  and  Phillips,  Outlines,  (fee.  p.  376. 


64:  ORIGIN   OF   GREAT   FAULTS.  [On.  V. 

as  would  have  been  produced  if  the  broken  ends  of  the  rock  had  been 
rubbed  along  the  plane  of  the  fault.*  In  the  Tynedale  and  Craven  faults, 
in  the  north  of  England,  the  vertical  displacement  is  still  greater,  and  the 
fracture  has  extended  in  a  horizontal  direction  for  a  distance  of  thirty 
miles  or  more.  Some  geologists  consider  it  necessary  to  imagine  that  the 
upward  or  downward  movement  in  these  cases  was  accomplished  at  a 
single  stroke,  and  not  by  a  series  of  sudden  but  interrupted  movements. 
This  idea  appears  to  have  been '  derived  from  a  notion  that  the  grooved 
walls  have  merely  been  rubbed  in  one  direction.  But  this  is  so  far  from 
being  a  constant  phenomenon  in  faults,  that  it  has  often  been  objected  to 
the  received  theory  respecting  those  polished  surfaces  called  "slicken- 
sides,"  that  the  striae  are  not  always  parallel,  but  often  curved  and  ir- 
regular. It  has,  moreover,  been  remarked,  that  not  only  the  walls  of 
the  fissure  or  fault,  but  its  earthy  contents,  sometimes  present  the  same 
polished  and  striated  faces.  Now  these  facts  seem  to  indicate  partial 
changes  in  the  direction  of  the  movement,  and  some  slidings  subsequent 
to  the  first  filling  up  of  the  fissure.  Suppose  the  mass  of  rock  A,  B,  C, 
to  overlie  an  extensive  chasm  d  e,  formed  at  the  depth  of  several  miles, 

Fig.  88. 


whether  by  the  gradual  contraction  in  bulk  of  a  melted  mass  passing  into 
a  solid  or  crystalline  state,  or  the  shrinking  of  argillaceous  strata,  baked 
by  a  moderate  heat,  or  by  the  subtraction  of  matter  by  volcanic  action,  or 
any  other  cause.  JSTow,  if  this  region  be  convulsed  by  earthquakes,  the 
fissures  /#,  and  others  at  right  angles  to  them,  may  sever  the  mass  B 
from  A  and  from  C,  so  that  it  may  move  freely,  and  begin  to  sink  into 
the  chasm.  A  fracture  may  be  conceived  so  clean  and  perfect  as  to 
allow  it  to  subside  at  once  to  the  bottom  of  the  subterranean  cavity ;  but 
it  is  far  more  probable  that  the  sinking  will  be  effected  at  successive 
periods  during  different  earthquakes,  the  mass  always  continuing  to  slide 
in  the  same  direction  along  the  planes  of  the  fissures  f  g,  and  the  edges 
of  the  falling  mass  being  continually  more  broken  and  triturated  at  each 
convulsion.  If,  as  is  not  improbable,  the  circumstances  which  have  caused 
the  failure  of  support  continue  in  operation,  it  may  happen  that  when  the 
mass  B  has  filled  the  cavity  first  formed,  its  foundations  will  again  give 
way  under  it,  so  that  it  will  fall  again  in  the  same  direction.  But,  if  the 
direction  should  change,  the  fact  could  not  be  discovered  by  observing 
the  slickensides,  because  the  last  scoring  would  efface  the  lines  of  previous 
friction.  In  the  present  state  of  our  ignorance  of  the  causes  of  subsidence, 
an  hypothesis  which  can  explain  the  great  amount  of  displacement  in 

*  Phillips,  Geology,  Lardner's  Cyclop,  p.  41. 


Cn.  V.]  ORIGIN    OF   GREAT   FAULTS.  65 

some  faults,  on  sound  mechanical  principles,  by  a  succession  of  move- 
ments, is  far  preferable  to  any  theory  which  assumes  each  fault  to  have 
been  accomplished  by  a  single  upcast  or  downthrow  of  several  thousand 
feet.  For  we  know  that  there  are  operations  now  in  progress,  at  great 
depths  in  the  interior  of  the  earth,  by  which  both  large  and  small  tracts 
of  ground  are  made  to  rise  above  and  sink  below  their  former  level,  some 
slowly  and  insensibly,  others  suddenly  and  by  starts,  a  few  feet  or  yards 
at  a  time  ;  'whereas  there  are  no  grounds  for  believing  that,  during  the 
last  3000  years  at  least,  any  regions  have  been  either  upheaved  or  de- 
pressed, at  a  single  stroke,  to  the  amount  of  several  hundred,  much  less 
several  thousand  feet.  When  some  of  the  ancient  marine  formations  are 
described  in  the  sequel,  it  will  appear  that  their  structure  and  organic 
contents  point  to  the  conclusion,  that  the  floor  of  the  ocean  was  slowly 
sinking  at  the  time  of  their  origin.  The  downward  movement  was  very 
gradual,  and  in  Wales  and  the  contiguous  parts  of  England  a  maximum 
thickness  of  32,000  feet  (more  than  six  miles)  of  Carboniferous,  Devonian, 
and  Silurian  rock  was  formed,  whilst  the  bed  of  the  sea  was  all  the  time 
continuously  and  tranquilly  subsiding.*  Whatever  may  have  been  the 
changes  which  the  solid  foundation  underwent,  whether  accompanied  by 
the  melting,  consolidation,  crystallization,  or  desiccation  of  subjacent  min- 
eral matter,  it  is  clear  from  the  fact  of  the  sea  having  remained  shallow 
all  the  while  that  the  bottom  never  sank  down  suddenly  to  the  depth  of 
many  hundred  feet  at  once. 

It  is  by  assuming  such  reiterated  variations  of  level,  each  separately  of 
small  vertical  amount,  but  multiplied  by  time  till  they  acquire  importance 
in  the  aggregate,  that  we  are  able  to  explain  the  phenomena  of  denuda- 
tion, which  will  be  treated  of  in  the  next  chapter.  By  such  movements 
every  portion  of  the  surface  of  the  land  becomes  in  its  turn  a  line  of  coast, 
and  is  exposed  to  the  action  of  the  waves  and  tides.  A  country  which  is 
undergoing  such  movement  is  never  allowed  to  settle  into  a  state  of  equi- 
librium, therefore  the  force  of  rivers  and  torrents  to  remove  or  excavate 
soil  and  rocky  masses  is  sustained  in  undiminished  energy. 

*  See  the  results  of  the  "  Geological  Survey  of  Great  Britain ;"  Memoir?,  yols. 
L  and  ii.  by  Sir  H.  de  la  Beche,  Mr.  A,  C.  Ramsay,  and  Mr.  John  Phillips. 

5 


66  DENUDATION  OF  ROCKS.  [On.  VL 


CHAPTER  VI. 

DENUDATION. 

Denudation  defined — Its  amount  equal  to  the  entire  mass  of  stratified  deposits  in 
the  earth's  crust — Horizontal  sandstone  denuded  in  Ross-shire — Levelled  sur- 
face of  countries  in  which  great  faults  occur — Coalbrook  Dale — Denuding  power 
of  the  ocean  during  the  emergence  of  land — Origin  of  Valleys — Obliteration  of 
sea-cliffs — Inland  sea-cliffs  and  terraces  in  the  Morea  and  Sicily — Limestone 
pillars  at  St.  Mihiel,  in  France — In  Canada — In  the  Bermudas. 

DENUDATION,  winch  has  been  occasionally  spoken  of  in  the  preceding 
chapters,  is  the  removal  of  solid  matter  by  water  in  motion,  whether  of 
rivers  or  of  the  waves  and  currents  of  the  sea,  and  the  consequent  laying 
bare  of  some  inferior  rock.  Geologists  have  perhaps  been  seldom  in  the 
habit  of  reflecting  that  this  operation  has  exerted  an  influence  on  the 
structure  of  the  earth's  crust  as  universal  and  important  as  sedimentary 
deposition  itself;  for  denudation  is  the  inseparable  accompaniment  of 
the  production  of  all  new  strata  of  mechanical  origin.  The  formation 
of  every  new  deposit  by  the  transport  of  sediment  and  pebbles  necessa- 
rily implies  that  there  has  been,  somewhere  else,  a  grinding  down  of  rock 
into  rounded  fragments,  sand,  or  mud,  equal  in  quantity  to  the  new 
strata.  All  deposition,  therefore,  except  in  the  case  of  a  shower  of  vol- 
canic ashes,  is  the  sign  of  superficial  waste  going  on  contemporaneously, 
and  to  an  equal  amount  elsewhere.  The  gain  at  one  point  is  no  more 
than  sufficient  to  balance  the  loss  at  some  other.  Here  a  lake  has  grown 
shallower,  there  a  ravine  has  been  deepened.  The  bed  of  the  sea  has  in 
one  region  been  raised  by  the  accumulation  of  new  matter,  in  another 
its  depth  has  been  augmented  by  the  abstraction  of  an  equal  quantity. 

When  we  see  a  stone  building,  we  know  that  somewhere,  far  or  near, 
a  quarry  has  been  opened.  The  courses  of  stone  in  the  building  may  be 
compared  to  successive  strata,  the  quarry  to  a  ravine  or  valley  which  has 
suffered  denudation.  As  the  strata,  like  the  courses  of  hewn  stone,  have 
been  laid  one  upon  another  gradually,  so  the  excavation  both  of  the 
valley  and  quarry  have  been  gradual.  To  pursue  the  comparison  still 
farther,  the  superficial  heaps  of  mud,  sand,  and  gravel,  usually  called 
alluvium,  may  be  likened  to  the  rubbish  of  a  quarry  which  has  been  re- 
jected as  useless  by  the  workmen,  or  has  fallen  upon  the  road  between 
the  quarry  and  the  building,  so  as  to  lie  scattered  at  random  over  the 
ground. 


Cn.  VI] 


DENUDATION   OF   STRATIFIED   ROCKS, 


67 


Fig.  89. 


If,  then,  the  entire  mass  of  stratified  deposits  in  the  earth's  crust  is  at 
once  the  monument  and  measure  of  the  denudation  which  has  taken 
place,  on  how  stupendous  a  scale  ought  we  to  find  the  signs  of 'this  re- 
moval of  transported  materials  in  past  ages!  Accordingly,  there  are 
different  classes  of  phenomena,  which  attest  in  a  most  striking  manner 
the  vast  spaces  left  vacant  by  the  erosive  power  of  water.  I  may  allude, 
first,  to  those  valleys  on  both  sides  of  which  the  same  strata  are  seen 
following  each  other  in  the  same  order,  and  having  the  same  mineral 
composition  and  fossil  contents.  We  may  observe,  for  example,  several 
formations,  as  Nos.  1,  2,  8,  4,  in  the  accom- 
panying diagram  (fig.  89) ;  No.  1  conglom- 
erate, No.  2  clay,  No.  3  grit,  and  No.  4 
limestone,  each  repeated  in  a  series  of  hills 
separated  by  valleys  varying  in  depth. 
When  we  examine  the  subordinate  parts  of 
these  four  formations,  we  find,  in  like  man- 
ner, distinct  beds  in  each,  corresponding,  on  the  opposite  sides  of  the 
valleys,  both  in  composition  and  order  of  position.  No  one  can  doubt 
that  the  strata  were  originally  continuous,  and  that  some  cause  has 
swept  away  the  portions  which  once  connected  the  whole  series.  A 
torrent  on  the  side  of  a  mountain  produces  similar  interruptions ;  and 
when  we  make  artificial  cuts  in  lowering  roads,  we  expose,  in  like  man- 
ner, corresponding  beds  on  either  side.  But  in  nature,  these  appearances 
occur  in  mountains  several  thousand  feet  high,  and  separated  by  inter- 
vals of  many  miles  or  leagues  in  extent,  of  which  a  grand  exemplifica- 
tion is  described  by  Dr.  MacCulloch,  on  the  northwestern  coast  of  Ross- 
shire,  in  Scotland.* 

Fig.  90. 

Coul  beg. 


Valleys  of  denudation. 
a.  alluvium. 


Suil  Yeini 


Coul  more. 


Denudation  of  red  sandstone  on  northwest  coast  of  Ross-shire.    (MacCulloch.) 

The  fundamental  rock  of  that  country  is  gneiss,  in  disturbed  strata,  on 
which  beds  of  nearly  horizontal  red  sandstone  rest  unconformably.  The 
latter  are  often  very  thin,  forming  mere  flags,  with  their  surfaces  dis- 
tinctly ripple-marked.  They  end  abruptly  on  the  declivities  of  many 
insulated  mountains,  which  rise  up  at  once  to  the  height  of  about  2000 
feet  above  the  gneiss  of  the  surrounding  plain  or  table-land,  and  to  an 
average  elevation  of  about  3000  feet  above  the  sea,  which  all  their  sum- 
mits generally  attain.  The  base  of  gneiss  varies  in  height,  so  that  the 
lower  portions  of  the  sandstone  occupy  different  levels,  and  the  thickness 
of  the  mass  is  various,  sometimes  exceeding  3000  feet.  It  is  impossible 
to  compare  these  scattered  and  detached  portions  without  imagining 
that  the  whole  country  has  once  been  covered  with  a  great  body  of  sand- 
stone, and  that  masses  from  1000  to  more  than  3000  feet  in  thickness  have 
been  removed. 

*  Western  Islands,  vol.  ii.  p.  93,  pi.  31,  fig.  4. 


68  DENUDATION.  [Cir.  VI 

In  the  "  Survey  of  Great  Britain"  (vol.  i.),  Professor  Ramsay  has  shown 
that  the  missing  beds,  removed  from  the  summit  of  the  Mendips,  must  have 
been  nearly  a  mile  in  thickness ;  and  he  has  pointed  out  considerable  areas 
in  South  Wales  and  some  of  the  adjacent  counties  of  England,  where 
a  series  of  primary  (or  palaeozoic)  strata,  not  less  than  11,000  feet  in 
thickness,  have  been  stripped  off.  All  these  materials  have  of  course 
been  transported  to  new  regions,  and  have  entered  into  the  composition 
of  more  modern  formations.  On  the  other  hand,  it  is  shown  by  obser- 
vations in  the  same  "Survey."  that  the  palaeozoic  strata  are  from  20,000 
to  30,000  feet  thick.  It  is  clear  that  such  rocks,  formed  of  mud  and 
sand,  now  for  the  most  part  consolidated,  are  the  monuments  of  denuding 
operations,  which  took  place  on  a  grand  scale  at  a  very  remote  period  in 
the  earth's  history.  For,  whatever  has  been  given  to  one  area  must  al- 
ways have  been  borrowed  from  another ;  a  truth  which,  obvious  as  it 
may  seem  when  thus  stated,  must  be  repeatedly  impressed  on  the  stu- 
dent's mind,  because  in  many  geological  speculations  it  is  taken  for 
granted  that  the  external  crust  of  the  earth  has  been  always  growing 
thicker,  in  consequence  of  the  accumulation,  period  after  period,  of  sedi- 
mentary matter,  as  if  the  new  strata  were  not  always  produced  at  the 
expense  of  pre-existing  rocks,  stratified  or  unstratified.  By  duly  reflect- 
ing on  the  fact,  that  all  deposits  of  mechanical  origin  imply  the  trans- 
portation from  some  other  region,  whether  contiguous  or  remote,  of  an 
equal  amount  of  solid  matter,  we  perceive  that  the  stony  exterior  of  the 
planet  must  always  have  grown  thinner  in  one  place  whenever,  by  acces- 
sions of  new  strata,  it  was  acquiring  density  in  another.  No  doubt  the 
vacant  space  left  by  the  missing  rocks,  after  extensive  denudation,  is  less 
imposing  to  the  imagination  than  a  vast  thickness  of  conglomerate  or 
sandstone,  or  the  bodily  presence  as  it  were  of  a  mountain-chain,  with 
all  its  inclined  and  curved  strata.  But  the  denuded  tracts  speak  a  clear 
and  emphatic  language  to  our  reason,  and,  like  repeated  layers  of  fossil 
nummulites,  corals  or  shells,  or  like  numerous  seams  of  coal,  each  based 
on  its  under  clay  full  of  the  roots  of  trees,  still  remaining  in  their  natural 
position,  demand  an  indefinite  lapse  of  time  for  their  elaboration. 

No  one  will  maintain  that  the  fossils  entombed  in  these  rocks  did  not 
belong  to  many  successive  generations  of  plants  and  animals.  In  like 
manner,  each  sedimentary  deposit  attests  a  slow  and  gradual  action,  and 
the  strata  not  only  serve  as  a  measure  of  the  amount  of  denudation 
simultaneously  effected  elsewhere,  but  are  also  a  correct  indication  of  the 
rate  at  which  the  denuding  operation  was  carried  on. 

Perhaps  the  most  convincing  evidence  of  denudation  on  a  magnificent 
scale  is  derived  from  the  levelled  surfaces  of  districts  where  large  faults 
occur.  I  have  shown,  in  fig.  87,  p.  63,  and  in  fig.  91,  how  angular  and 
protruding  masses  of  rock  might  naturally  have  been  looked  for  on  the 
surface  immediately  above  great  faults,  although  in  fact  they  rarely 
exist.  This  phenomenon  may  be  well  studied  in  those  districts  where 
coal  has  been  extensively  worked,  for  there  the  former  relation  of  the 
beds  which  have  shifted  their  position  may  be  determined  with  great  ac- 


CIL  VL] 


OF  STRATIFIED   ROCKS. 


69 


curacy.     Thus  in  the  coal  field  of  Ashby  de  la  Zouch,  in  Leicestershire 
(see  fig.  91),  a  fault  occurs,  on  one  side  of  which  the  'coal  beds  abed 

Fig.  91.  —     * 


Faults  and  denuded  coal  strata,  Ashby  de  la  Zouch.    (Mammat.) 

rise  to  the  height  of  500  feet  above  the  corresponding  beds  on  the  other 
side.  But  the  uplifted  strata  do  not  stand  up  500  feet  above  the  general 
surface  ;  on  the  contrary,  the  outline  of  the  country,  as  expressed  by  the 
line  z  z,  is  uniformly  undulating  without  any  break,  and  the  mass  indicated 
by  the  dotted  outline  must  have  been  washed  away.*  There  are  proofs 
of  this  kind  in  some  level  countries,  where  dense  masses  of  strata  have 
been  cleared  away  from  areas  several  hundred  square  miles  in  extent. 

In  the  Newcastle  coal  district  it  is  ascertained  that  faults  occur  in 
which  the  upward  or  downward  movement  could  not  have  been  less  than 
140  fathoms,  which,  had  they  affected  the  configuration  of  the  surface  to 
an  equal  amount,  would  produce  mountains  with  precipitous  escarpments 
nearly  1000  feet  high,  or  chasms  of  the  like  depth ;  yet  is  the  actual  level 
of  the  country  absolutely  uniform,  affording  no  trace  whatever  of  subter- 
ranean movements.f 

The  ground  from  which  these  materials  have  been  removed  is  usually 
overspread  with  heaps  of  sand  and  gravel,  formed  out  of  the  ruins  of 
the  very  rocks  which  have  disappeared.  Thus,  in  the  districts  above  re- 
ferred to,  they  consist  of  rounded  and  angular  fragments  of  hard  sand- 
stone, limestone,  and  ironstone,  with  a  small  quantity  of  the  more 
destructible  shale,  and  even  rounded  pieces  of  coal. 

Allusion  has  been  already  made  to  the  shattered  state  and  discordant 
.position  of  the  carboniferous  strata  in  Coalbrook  Dale  (p.  62).  The 
collier  cannot  proceed  three  or  four  yards  without  meeting  with  small 
slips,  and  from  time  to  time  he  encounters  faults  of  considerable  magni- 
tude, which  have  thrown  the  rocks  up  or  down  several  hundred  feet. 
Yet  the  superficial  inequalities  to  which  these  dislocated  masses  origi- 
nally gave  rise  are  no  longer  discernible,  and  the  comparative  flatness  of 
the  existing  surface  can  only  be  explained,  as  Mr.  Prestwich  has  observed, 
by  supposing  the  fractured  portions  to  have  been  removed  by  water.  It 
is  also  clear  that  strata  of  red  sandstone,  more  than  1000  feet  thick, 
which  once  covered  the  coal,  in  the  same  region,  have  been  carried  away 


*  See  Mammal's  Geological  Facts,  &c.,  p.  90,  and  plate, 
f  Conybeare's  Report  to  Brit.  Assoc.  1842,  p.  381. 


TO  ORIGIN  OF  VALLEYS.  [Cut.  VI 

from  large  areas.  That  water  has,  in  this  case,  been  the  denuding  agent, 
we  may  infer  from  the  fact  that  the  rocks  have  yielded  according  to  their 
different  degrees  of  hardness ;  the  hard  trap  of  the  Wreldn,  for  example, 
and  other  hills,  having  resisted  more  than  the  softer  shale  and  sandstone, 
so  as  now  to  stand  out  in  bold  relief.* 

Origin  of  valleys. — Many  of  the  earlier  geologists,  and  Dr.  Hutton 
among  them,  taught  that  "  rivers  have  in  general  hollowed  out  their  val- 
leys." This  is  no  doubt  true  of  rivulets  and  torrents  which  are  the  feeders 
of  the  larger  streams,  and  which,  descending  over  rapid  slopes,  are  most 
subject  to  temporary  increase  and  diminution  in  the  volume  of  their 
waters.  It  must  also  be  admitted  that  the  quantity  of  mud,  sand,  and 
pebbles  constituting  many  a  modern  delta  is  so  considerable,  as  to  prove 
that  a  very  large  part  of  the  inequalities  now  existing  on  the  earth's 
surface  are  due  to  fluviatile  action ;  but  the  principal  valleys  in  almost 
every  great  hydrographical  basin  in  the  world,  are  of  a  shape  and  magni- 
tude which  imply  that  they  have  been  due  to  other  causes  besides  the 
mere  excavating  power  of  rivers. 

Some  geologists  have  imagined  that  a  deluge,  or  succession  of  deluges, 
may  have  been  the  chief  denuding  agency,  and  they  have  speculated  on  a 
series  of  enormous  waves  raised  by  the  instantaneous  upthrow  of  continents 
or  mountain  chains  out  of  the  sea.  But  even  were  we  disposed  to  grant 
such  sudden  upheavals  of  the  floor  of  the  ocean,  and  to  assume  that  great 
waves  would  be  the  consequence  of  each  convulsion,  it  is  not  easy  to  ex- 
plain the  observed  phenomena  by  the  aid  of  so  gratuitous  an  hypothesis. 

On  the  other  hand,  a  machinery  of  a  totally  different  kind  seems  capa- 
ble of  giving  rise  to  effects  of  the  required  magnitude.  It  has  now  been 
ascertained  that  the  rising  and  sinking  of  extensive  portions  of  the  earth's 
crust,  whether  insensibly  or  by  a  repetition  of  sudden  shocks,  is  part  of 
the  actual  course  of  nature,  and  we  may  easily  comprehend  how  the 
land  may  have  been  exposed  during  these  movements  to  abrasion  by  the 
waves  of  the  sea.  In  the  same  manner  as  a  mountain  mass  may,  in  the 
course  of  ages,  be  formed  by  sedimentary  deposition,  layer  after  layer,  so 
masses  equally  voluminous  may  in  time  waste  away  by  inches  ;  as,  for 
example,  if  beds  of  incoherent  materials  are  raised  slowly  in  an  open  sea 
where  a  strong  current  prevails.  It  is  well  known  that  some  of  these 
oceanic  currents  have  a  breadth  of  200  miles,  and  that  they  sometimes 
run  for  a  thousand  miles  or  more  in  one  direction,  retaining  a  considera- 
ble velocity  even  at  the  depth  of  several  hundred  feet.  Under  these  cir- 
cumstances, the  flowing  waters  may  have  power  to  clear  away  each 
stratum  of  incoherent  materials  as  it  rises  and  approaches  the  surface, 
where  the  waves  exert  the  greatest  force ;  and  in  this  manner  a  volu- 
minous deposit  may  be  entirely  swept  away,  so  that,  in  the  absence  of 
faults,  no  evidence  may  remain  of  the  denuding  operation.  It  may  in- 
deed be  affirmed  that  the  signs  of  waste  will  usually  be  least  obvious 
where  the  destruction  has  been  most  complete ;  for  the  annihilation 

*  Prestwich,  Geol.  Trans,  second  series,  vol.  v.  pp.  452,  473v 


CH.  VI]  INLAND   SEA-CLIFFS.  71 

may  have  proceeded  so  far,  that  no  ruins  are  left  of  the  dilapidated 
rocks. 

Although  denudation  has  had  a  levelling  influence  on  some  countries 
of  shattered  and  disturbed  strata  (see  fig.  87,  p.  63,  and  fig.  91,  p.  69), 
it  has  more  commonly  been  the  cause  of  superficial  inequalities,  espe- 
cially in  regions  of  horizontal  stratification.  The  general  outline  of  these 
regions  is  that  of  flat  and  level  platforms,  interrupted  by  valleys  often  of 
considerable  depth,  and  ramifying  in  various  directions.  These  hollows 
may  once  have  formed  bays  and  channels  between  islands,  and  the 
steepest  slope  on  the  sides  of  each  valley  may  have  been  a  sea-cliff,  which 
was  undermined  for  ages,  as  the  land  emerged  gradually  from  the  deep. 
We  may  suppose  the  position  and  course  of  each  valley  to  have  been 
originally  determined  by  differences  in  the  hardness  of  the  rocks,  and  by 
rents  and  joints  which  usually  occur  even  in  horizontal  strata.  In  mountain 
chains,  such  as  the  Jura  before  described  (see  fig.  71,  p.  55),  we  perceive 
at  once  that  the  principal  valleys  have  not  been  due  to  aqueous  excava- 
tion, but  to  those  mechanical  movements  which  have  bent  the  rocks  into 
their  present  form.  Yet  even  in  the  Jura  there  are  many  valleys,  such 
as  C  (fig.  71),  which  have  been  hollowed  out  by  water ;  and  it  may  be 
stated  that  in  every  part  of  the  globe  the  unevenness  of  the  surface  of 
the  land  has  been  due  to  the  combined  influence  of  subterranean  move- 
ments and  denudation. 

I  may  now  recapitulate  a  few  of  the  conclusions  to  which  we  have  ar- 
rived :  first,  all  the  mechanical  strata  have  been  accumulated  gradually, 
and  the  concomitant  denudation  has  been  no  less  gradual :  secondly,  the 
dry  land  consists  in  great  part  of  strata  formed  originally  at  the  bottom 
of  the  sea,  and  has  been  made  to  emerge  and  attain  its  present  height 
by  a  force  acting  from  beneath  :  thirdly,  no  combination  of  causes  has 
yet  been  conceived  so  capable  of  producing  extensive  and  gradual  denu- 
dation, as  the  action  of  the  waves  and  currents  of  the  ocean  upon  land 
slowly  rising-  out  of  the  deep. 

Now,  if  we  adopt  these  conclusions,  we  shall  naturally  be  led  to  look 
everywhere  for  marks  of  the  former  residence  of  the  sea  upon  the  land, 
especially  near  the  coasts  from  which  the  last  retreat  of  the  waters  took 
place,  and  it  will  be  found  that  such  signs  are  not  wanting. 

I  shall  have  occasion  to  speak  of  ancient  sea-cliffs,  now  far  inland,  in 
the  southeast  of  England,  when  treating  in  Chapter  XLX.  of  the  denu- 
dation of  the  chalk  in  Surrey,  Kent,  and  Sussex.  Lines  of  upraised 
sea-beaches  of  more  modern  date  are  traced,  at  various  levels  from  20  to 
100  feet  and  upwards  above  the  present  sea-level,  for  great  distances  on 
the  east  and  west  coasts  of  Scotland,  as  well  as  in  Devonshire,  and  othei 
counties  in  England.  These  ancient  beach-lines  often  form  terraces  ol 
sand  and  gravel,  including  littoral  shells,  some  broken,  others  entire,  and 
corresponding  with  species  now  living  on  the  adjoining  coast.  But  it 
would  be  unreasonable  to  expect  to  meet  everywhere  with  the  signs  of 
ancient  shores,  since  no  geologist  can  have  failed  to  observe  how  soon  all 
recent  marks  of  the  kind  above  alluded  to  are  obscured  or  entirely  ef- 


72  INLAND    SEA-CLIFFS.  [On.  VI 

faced,  wherever,  in  consequence  of  the  altered  state  of  the  tides  and  cur- 
rents, the  sea  has  receded  for  a  few  centuries.  We  see  the  cliffs  crumble 
down  in  a  few  years  if  composed  of  sand  or  clay,  and  soon  reduced  to  a 
gentle  slope.  If  there  were  shells  on  the  beach  they  decompose,  and 
their  materials  are  washed  away,  after  which  the  sand  and  shingle  may 
resemble  any  other  alluviums  scattered  over  the  interior. 

The  features  of  an  ancient  shore  may  sometimes  be  concealed  by  the 
growth  of  trees  and  shrubs,  or  by  a  covering  of  blown  sand,  a  good  ex- 
ample of  which  occurs  a  few  miles  west  from  Dax,  near  Bourdeaux,  in 
the  south  of  France.  About  twelve  miles  inland,  a  steep  bank  may  be 
traced  running  in  a  direction  nearly  northeast  and  southwest,  or  parallel 
to  the  contiguous  coast.  This  sudden  fall  of  about  50  feet  conducts  us 
fiom  the  higher  platform  of  the  Landes  to  a  lower  plain  which  extends 

Fig.  92. 


Section  of  inland  cliff  at  Abesse,  near  Dax. 
a.  Sand  of  the  Landes.  &.  Limestone.  c.  Clay. 

to  the  sea.  The  outline  of  the  ground  suggested  to  me,  as  it  would  do 
to  every  geologist,  the  opinion  that  the  bank  in  question  was  once  a  sea- 
cliff,  when  the  whole  country  stood  at  a  lower  level.  But  this  is  no 
longer  matter  of  conjecture,  for,  in  making  excavations  in  1830  for  the 
foundation  of  a  building  at  Abesse,  a  quantity  of  loose  sand,  which 
.formed  the  slope  d  e,  was  removed  ;  and  a  perpendicular  cliff,  about  50 
feet  in  height,  which  had  hitherto  been  protected  from  the  agency  of  the 
elements,  was  exposed.  At  the  bottom  appeared  the  limestone  6,  con- 
taining tertiary  shells  and  corals,  immediately  below  it  the  clay  c,  and 
above  it  the  usual  tertiary  sand  a,  of  the  department  of  the  Landes.  At 
the  base  of  the  precipice  were  seen  large  partially  rounded  masses  of 
rock,  evidently  detached  from  the  stratum  b.  The  face  of  the  limestone 
was  hollowed  out  and  weathered  into  such  forms  as  are  seen  in  the  cal- 
careous cliffs  of  the  adjoining  coast,  especially  at  Biaritz,  near  Bayonne. 
It  is  evident  that,  when  this  country  stood  at  a  somewhat  lower  level,  the 
sea  advanced  along  the  surface  of  the  argillaceous  stratum  c,  which,  from 
its  yielding  nature,  favored  the  waste  by  allowing  the  more  solid  super- 
incumbent stone  6  to  be  readily  undermined.  Afterwards,  when  the 
country  had  been  elevated,  part  of  the  sand,  a,  fell  down,  or  was  drifted 
by  the  winds,  so  as  to  form  the  talus,  d  e,  which  masked  the  inland  cliff 
until  it  was  artificially  laid  open  to  view. 

When  we  are  considering  the  various  causes  which,  in  the  course  of 
ages,  may  efface  the  characters  of  an  ancient  sea-coast,  earthquakes  must 
not  be  forgotten.  During  violent  shocks,  steep  and  overhanging  cliffs 
are  often  thrown  down  and  become  a  heap  of  ruins.  Sometimes  une- 
qual movements  of  upheaval  or  depression  entirely  destroy  that  horizon- 


Cn.   n.]  INLAND   SEA-CLIFFS  AND  TERRACES.  78 

tality  of  the  base-line  which  constitutes  the  chief  peculiarity  of  an 
ancient  sea-cliff. 

It  is,  however,  in  countries  where  hard  limestone  rocks  abound,  that 
inland  cliffs  retain  faithfully  the  characters  which  they  acquired  when 
they  constituted  the  boundary  of  land  and  sea.  Thus,  in  the  Morea,  no 
less  than  three,  or  even  four,  ranges  of  what  were  once  sea-cliffs  are  well 
preserved.  These  have  been  described,  by  MM.  Boblaye  and  Virlet,  as 
rising  one  above  the  other  at  different  distances  from  the  actual  shore, 
the  summit  of  the  highest  and  oldest  occasionally  exceeding  1000  feet 
in  elevation.  At  the  base  of  each  there  is  usually  a  terrace,  which  is  in 
some  places  a  few  yards,  in  others  above  300  yards  wide,  so  that  we  are 
conducted  from  the  high  land  of  the  interior  to  the  sea  by  a  succession 
of  great  steps.  These  inland  cliffs  are  most  perfect,  and  most  exactly  re- 
semble those  now  washed  by  the  waves  of  the  Mediterranean,  where 
they  are  formed  of  calcareous  rock,  especially  if  the  rock  be  a  hard  crys- 
talline marble.  The  following  are  the  points  of  correspondence  observed 
between  the  ancient  coast  lines  and  the  borders  of  the  present  sea: — 1.  A 
range  of  vertical  precipices,  with  a  terrace  at  their  base.  2.  A  weathered 
state  of  the  surface  of  the  naked  rock,  such  as  the  spray  of  the  sea  pro- 
duces. 3.  A  line  of  littoral  caverns  at  the  foot  of  the  cliffs.  4.  A  con- 
solidated beach  or  breccia  with  occasional  marine  shells,  found  at  the 
base  of  the  cliffs,  or  in  the  caves.  5.  Lithodomous  perforations. 

In  regard  to  the  first  of  these,  it  would  be  superfluous  to  dwell  on  the 
evidence  afforded  of  the  undermining  power  of  waves  and  currents  by 
perpendicular  precipices.  The  littoral  caves,  also,  will  be  familiar  to 
those  who  have  had  opportunities  of  observing  the  manner  in  which  the 
waves  of  the  sea,  when  they  beat  against  rocks,  have  power  to  scoop  out 
caverns.  As  to  the  breccia,  it  is  composed  of  pieces  of  limestone  and 
rolled  fragments  of  thick  solid  shell,  such  as  Strombus  and  Spondylus, 
all  bound  together  by  a  crystalline  calcareous  cement.  Similar  aggrega- 
tions are  now  forming  on  the  modern  beaches  of  Greece,  and  in  caverns 
on  the  sea-side;  and  they  are  only  distinguishable  in  character  from 
those  of  more  ancient  date,  by  including  many  pieces  of  pottery.  In 
regard  to  the  lithodomi  above  alluded  to,  these  bivalve  mollusks  are  well 
known  to  have  the  power  of  excavating  holes  in  the  hardest  limestones, 
the  size  of  the  cavity  keeping  pace  with  the  growth  of  the  shell.  When 
living  they  require  to  be  always  covered  by  salt  water,  but  similar  pear- 
shaped  hollows,  containing  the  dead  shells  of  these  creatures,  are  found 
at  different  heights  on  the  face  of  the  inland  cliffs  above  mentioned. 
Thus,  for  example,  they  have  been  observed  near  Modon  and  Xavarino 
on  cliffs  in  the  interior  125  feet  high  above  the  Mediterranean.  As  to 
the  weathered  surface  of  the  calcareous  rocks,  all  limestones  are  known 
to  suffer  chemical  decomposition  when  moistened  by  the  spray  of.  the 
salt  water,  and  are  corroded  still  more  deeply  at  points  lower  down  where 
they  are  just  reached  by  the  breakers.  By  this  action  the  stone  acquires 
a  wrinkled  and  furrowed  outline,  and  very  near  the  sea  it  becomes  rough 
and  branching,  as  if  covered  with  corals.  Such  effects  are  traced  not 


74  INLAND   SEA-CLIFFS  [On.  VI 

only  on  the  present  shore,  but  at  the  base  of  the  ancient  cliffs  far  in  the 
interior.  Lastly,  it  remains  only  to  speak  of  the  terraces,  which  extend 
with  a  gentle  slope  frorn  the  base  of  almost  all  the  inland  cliffs,  and  are 
for  the  most  part  narrow  where  the  rock  is  hard,  but  sometimes  half  a 
mile  or  more  in  breadth  where  it  is  soft.  They  are  the  effects  of  the 
encroachment  of  the  ancient  sea  upon  the  shore  at  those  levels  at  which 
the  land  remained  for  a  long  time  stationary.  The  justness  of  this  view 
is  apparent  on  examining  the  shape  of  the  modern  shore  wherever  the 
sea  is  advancing  upon  the  land,  and  removing  annually  small  portions 
of  undermined  rock.  By  this  agency  a  submarine  platform  is  produced 
on  which  we  may  walk  for  some  distance  from  the  beach  in  shallow 
water,  the  increase  of  depth  being  very  gradual,  until  we  reach  a  point 
where  the  bottom  plunges  down  suddenly.  This  platform  is  widened 
with  more  or  less  rapidity  according  to  the  hardness  of  the  rocks,  and 
when  upraised  it  constitutes  an  inland  terrace. 

But  the  four  principal  lines  of  cliff  observed  in  the  Morea  do  not 
imply,  as  some  have  imagined,  four  great  eras  of  sudden  upheaval ;  they 
simply  indicate  the  intermittance  of  the  upheaving  force.  Had  the  rise 
of  the  land  been  continuous  and  uninterrupted,  there  would  have  been 
no  one  prominent  line  of  cliff;  for  every  portion  of  the  surface  having 
been,  in  its  turn,  and  for  an  equal  period  of  time,  a  sea-ehore,  would 
have  presented  a  nearly  similar  aspect.  But  if  pauses  occur  in  the  pro- 
cess of  upheaval,  the  waves  and  currents  have  time  to  sap,  throw  down, 
and  clear  away  considerable  masses  of  rock,  and  to  shape  out  at  several 
successive  levels  lofty  ranges  of  cliffs  with  broad  terraces  at  their  base. 

There  are  some  levelled  spaces,  however,  both  ancient  and  modern,  in 
the  Morea,  which  are  not  due  to  denudation,  although  resembling  in 
outline  the  terraces  above  described.  They  may  be  called  Terraces  of 
Deposition,  since  they  have  resulted  from  the  gain  of  land  upon  the  sea 
where  rivers  and  torrents  have  produced  deltas.  If  the  sedimentary 
matter  has  filled  up  a  bay  or  gulf  surrounded  by  steep  mountains,  a  flat 
plain  is  formed  skirting  the  inland  precipices ;  and  if  these  deposits  are 
upraised,  they  form  a  feature  in  the  landscape  very  similar  to  the  areas 
of  denudation  before  described. 

In  the  island  of  Sicily  I  have  examined  many  inland  cliffs  like  those 
of  the  Morea  ;  as,  for  example,  near  Palermo,  where  a  precipice  is  seen 
consisting  of  limestone,  at  the  base  of  which  are  numerous  caves.  One 
of  these,  called  San  Giro,  about  2  miles  distant  from  Palermo,  is  about 
20  feet  high,  10  wide,  and  180  above  the  sea.  Within  it  is  found  an 
ancient  beach  (6,  fig.  93),  formed  of  pebbles  of  various  rocks,  many  of 
which  must  have  come  from  places  far  remote.  Broken  pieces  of  coral 
and  shell,  especially  of  oysters  and  pectens,  are  seen  intermingled  with 
the  pebbles.  .  Immediately  above  the  level  of  this  beach,  serpulce  are 
still  found  adhering  to  the  face  of  the  rock,  and  the  limestone  is  perfo- 
rated by  lithodomi.  Within  the  grotto,  also,  at  the  same  level,  similar 
perforations  occur ;  and  so  numerous  are  the  holes,  that  the  rock  is  com- 
pared by  Hoffmann  to  a  target  pierced  by  musket  balls.  But  in  ordei 


On.  VI] 


IN  THE  ISLAND  OF  SICILY. 


75 


to  expose  to  view  these  marks  of  boring-shells  in  the  interior  of  the  cave, 
it  was  necessary  first  to  remove  a  mass  of  breccia,  which  consisted  of 


Fig.  93. 


a.  Monte  Grifone.  6.  Cave  of  San  Ciro.* 

c.  Plain  of  Palermo,  in  \vhich  are  Newer  Pliocene  strata  of 
limestone  and  sand.  d.  Bay  of  Palermo. 

numerous  fragments  of  rock,  and  an  immense  quantity  of  bones  of  the 
mammoth,  hippopotamus,  and  other  quadrupeds,  imbedded  in  a  dark 
brown  calcareous  marl.  Many  of  the  bones  were  rolled,  as  if  partially 
subjected  to  the  action  of  the  waves.  Below  this  breccia,  which  is  about 
20  feet  thick,  was  found  a  bed  of  sand  filled  with  sea-shells  of  recent 
species  ;  and  underneath  the  sand,  again,  is  the  secondary  limestone  of 
Monte  Grifone.  The  state  of  the  surface  of  the  limestone  in  the  cave 
above  the  level  of  the  marine  sand  is  very  different  from  that  below  it. 
Above,  the  rock  is  jagged  and  uneven,  as  is  usual  in  the  roofs  and  sides 
of 'limestone  caverns;  below,  the  surface  is  smooth  and  polished,  as  if 
by  the  attrition  of  the  waves. 

The  platform  indicated  at  c,  fig.  93,  is  formed  by  a  tertiary  deposit 
containing  marine  shells  almost  all  of  living  species,  and  it  affords  an 
illustration  of  the  terrace  of  deposition,  or  the  last  of  the  two  kinds  be- 
fore mentioned  (p.  74). 

There  are  also  numerous  instances  in  Sicily  of  terraces  of  denudation. 
One  of  these  occurs  on  the  east  coast  to  the  north  of  Syracuse,  and  the 
same  is  resumed  to  the  south  beyond  the  town  of  Noto,  where  it  may 
be  traced  forming  a  continuous  and  lofty  precipice,  a  5,  fig.  94,  facing 
towards  the  sea,  and  constituting  the  abrupt  termination  of  a  calcareous 
formation,  which  extends  in  horizontal  strata  far  inland.  This  precipice 
varies  in  height  from  500  to  700  feet,  and  between  its  base  and  the  sea 
is  an  inferior  platform,  c  6,  consisting  of  similar  white  limestone.  All 
the  beds  dip  towards  the  sea,  but  are  usually  inclined  at  a  very  slight 
angle :  they  are  seen  to  extend  uninterruptedly  from  the  base  of  the 
escarpment  into  the  platform,  showing  distinctly  that  the  lofty  cliff  was 
not  produced  by  a  fault  or  vertical  shift  of  the  beds,  but  by  the  removal 
of  a  considerable  mass  of  rock.  Hence  we  may  conclude  that  the  sea, 
which  is  now  undermining  the  cliffs  of  the  Sicilian  coast,  reached  at 
some  former  period  the  base  of  the  precipice  a  6,  at  which  time  the  sur- 

*  Section  given  by  Dr.  Christie,  Edin.  New  PhiL  Journ.  No.  xxm.  called  by 
mistake  the  Cave  of  Mardolce,  by  the  late  M.  Hoffmann.  See  account  by  Mr.  S. . 
P.  Pratt,  F.  G.  S.  Proceedings  of  Geol.  Soc.  No.  32,  1S3S. 


76 


INLAND   SEA- CLIFFS  AND 


[On.  VI. 


face  of  the  terrace  c  b  must  have'  been  covered  by  the  Mediterranean. 
There  was  a  pause,  therefore,  in  the  upward  movement,  when  the  waves 

Fig.  94. 


Sea 


of  the  sea  had  time  to  carve  out  the  platform  c  b ;  but  there  may  have 
been  many  other  stationary  periods  of  minor  duration.  Suppose,  for 
example,  that  a  series  of  escarpments  e,  f,  g,  A,  once  existed,  and  that 
the  sea,  during  a  long  interval  free  from  subterranean  movements, 
advances  along  the  line  c  6,  all  preceding  cliffs  must  have  been 
swept  away  one  after  the  other,  and  reduced  to  the  single  precipice 
ab. 

That  such  a  series  of  smaller  cliffs,  as  those  represented  at  e,  /,  g,  A, 
fig.  94,  did  really  once  exist  at  intermediate  heights  in  place  of  the  single 
precipice  a  6,  is  rendered  highly  probable  by  the  fact,  that  in  certain 
bays  and  inland  valleys  opening  towards  the  east  coast  of  Sicily,  and  not 
far  from  the  section  given  in  fig.  94,  the  solid  limestone  is  shaped  out 
into  a  great  succession  of  ledges,  separated  from  each  other  by  small 
vertical  cliffs.  These  are  sometimes  so  numerous,  one  above  the  other, 


Fig.  95. 


Valley  called  Gozzo  degli  Martiri,  below  Melilli,  Val  di  Note. 

that  where  there  is  a  bend  at  the  head  of  a  valley,  they  produce  an  ef- 
fect singularly  resembling  the  seats  of  a  Roman  amphitheatre.     A  good 


CH.  VI.]  TEREACES   IX   SICILY.  77 

example  of  this  configuration  occurs  near  the  town  of  Melilli,  as 
seen  in  the  annexed  view  (fig.  95).  In  the  south  of  the  island,  near 
Spaccaforno,  Scicli,  and  Modica,  precipitous  rocks  of  white  limestone, 
ascending  to  the  height  of  500  feet,  have  been  carved  out  into  similar 
forms. 

This  appearance  of  a  range  of  marble  seats  circling  round  the  head  of 
a  valley,  or  of  great  flights  of  steps  descending  from  the  top  to  the  bot- 
tom, on  the  opposite  sides  of  a  gorge,  may  be  accounted  for,  as  already 
hinted,  bv  supposing  the  sea  to  have  stood  successively  at  many  different 
levels,  as  at  a  a,  b  5,  c  c,  in  the  accompanying  fig.  96.  But  the  causes 
of  the  gradual  contraction  of  the  valley  from  above  downwards  may 

Fig.  96. 


still  be  matter  of  speculation.  Such  contraction  may  be  due  to  the 
greater  force  exerted  by  the  waves  when  the  land  at  its  first  emergence 
was  smaller  in  quantity,  and  more  exposed  to  denudation  in  an  open 
sea ;  whereas  the  wear  and  tear  of  the  rocks  might  diminish  in  propor 
tion  as  this  action  became  confined  within  bays  or  channels  closed  in  on 
two  or  three  sides.  Or,  secondly,  the  separate  movements  of  elevation 
may  have  followed  each  other  more  rapidly  as  the  land  continued  to  rise, 
so  that  the  times  of  those  pauses,  during  which  the  greatest  denudation 
was  accomplished  at  certain  levels,  were  always  growing  shorter.  It 
should  be  remarked,  that  the  cliffs  and  small  terraces  are  rarely  found  on 
the  opposite  sides  of  the  Sicilian  valleys  at  heights  so  precisely  answering 
to  each  other  as  those  given  in  fig.  96,  and  this  might  have  been  ex- 
pected, to  whichever  of  the  two  hypotheses  above  explained  we  incline  ; 
for,  according  to  the  direction  of  the  prevailing  winds  and  currents,  the 
waves  may  beat  with  unequal  force  on  different  parts  of  the  shore,  so 
that  while  no  impression  is  made  on  one  side  of  a  bay,  the  sea  may 
encroach  so  far  on  the  other  as  to  unite  several  smaller  cliffs  into 
one. 

Before  quitting  the  subject  of  ancient  sea-cliffs,  carved  out  of  lime- 
stone, I  shall  mention  the  range  of  precipitous  rocks,  composed  of  a 
white  marble  of  the  Oolitic  period,  which  I  have  seen  near  the  northern 
gate  of  St.  Mihiel  in  France.  They  are  situated  on  the  right  bank  of 
the  Meuse,  at  a  distance  of  200  miles  from  the  nearest  sea,  and  they 
present  on  the  precipice  facing  the  river  three  or  four  horizontal  grooves, 
one  above  the  other,  precisely  resembling  those  which  are  scooped  out 
by  the  undermining  waves.  The  summits  of  several  of  these  masses  are 
detached  from  the  adjoining  hill,  in  which  case  the  grooves  pass  all 


78 


KOCKS  WORN  BY  THE  SEA. 


[On.  VI 


round  them,  facing  towards  all  points  of  the  compass,  as  if  they  had 
once  formed  rocky  islets  near  the  shore.* 

Captain  Bayfield,  in  his  survey  of  the  Gulf  of  St.  Lawrence,  discov- 
ered in  several  places,  especially  in  the  Mingan  islands,  a  counterpart  of 
the  inland  cliffs  of  St.  Mihiel,  and  traced  a  succession  of  shingle  beaches, 
one  above  the  other,  which  agreed  in  their  level  with  some  of  the  prin- 
cipal grooves  scooped  out  of  the  limestone  pillars.  These  beaches  con- 
sisted of  calcareous  shingle,  with  shells  of  recent  species,  the  farthest 
from  the  shore  being  60  feet  above  the  level  of  the  highest  tides.  In 
addition  to  the  drawings  of  the  pillars  called  the  flower-pots,  which  he 
has  published,!  I  have  been  favored  with  other  views  of  rocks  on  the 
same  coast,  drawn  by  Lieut.  A.  Bo  wen,  R.  N.  (See  fig.  97.^1 

Fig.  97. 


Limestone  columns  in  Niaplsca  Island,  in  the  Gulf  of  St.  Lawrence.    Height 
of  the  second  column  on  the  left,  60  feet. 

In  the  North- American  beaches  above  mentioned  rounded  fragments 
of  limestone  have  been  found  perforated  by  lithodomi ;  and  holes  drilled 
by  the  same  mollusks  have  been  detected  in  the  columnar  rocks  or 
"  flower-pots,"  showing  that  there  has  been  no  great  amount  of  atmos- 
pheric decomposition  on  the  surface,  or  the  cavities  alluded  to  would 
have  disappeared. 

Fig.  98. 


The  North  Eocks,  Bermuda,  lying  outside  the  great  coral  reef. 
A.  16  feet  high,  and  B.  12  feet.  c.  c.  Hollows  worn  by  the  sea. 

*  I  was  directed  by  M.  Deshayes  to  this  spot,  which  I  visited  in  June,  1833. 
f  See  Trans,  of  Geol.  Soc.  second  series,  vol.  v.  plate  v. 


CH.  VII.]  '  ALLUVIUM.  79 

We  have  an  opportunity  of  seeing  in  the  Bermuda  islands  the  manner 
in  which  the  waves  of  the  Atlantic  have  worn,  and  are  now  wearing  out, 
deep  smooth  hollows  on  every  side  of  projecting  masses  of  hard  limestone. 
In  the  annexed  drawing,  communicated  to  me  by  Capt.  Nelson,  R.  E.,  the 
excavations  c,  c,  c,  have  been  scooped  out  by  the  waves  in  a  stone  of  very 
modern  date,  which,  although  extremely  hard,  is  full  of  recent  corals  and 
shells,  some  of  which  retain  their  color. 

When  the  forms  of  these  horizontal  grooves,  of  which  the  surface  is 
sometimes  smooth  and  almost  polished,  and  the  roofs  of  which  often 
overhang  to  the  extent  of  5  feet  or  more,  have  been  carefully  studied  by 
geologists,  they  will  serve  to  testify  the  former  action  of  the  waves  at 
innumerable  points  far  in  the  interior  of  the  continents.  But  we  must 
learn  to  distinguish  the  indentations  due  to  the  original  action  of  the  sea, 
and  those  caused  by  subsequent  chemical  decomposition  of  calcareous 
rocks,  to  which  they  are  liable  in  the  atmosphere. 

I  shall  conclude  with  a  warning  to  beginners  not  to  feel  surprise  if  they 
can  detect  no  evidence  of  the  former  sojourn  of  the  sea  on  lands  which 
we  are  nevertheless  sure  have  been  submerged  at  periods  comparativb.y 
modem ;  for  notwithstanding  the  enduring  nature  of  the  marks  left  by 
littoral  action  on  calcareous  rocks,  we  can  by  no  means  detect  sea-beaches 
and  inland  cliffs  everywhere,  even  in  Sicily  and  the  Morea.  On  the  con 
trary,  they  are,  upon  the  whole,  extremely  partial,  and  are  often  entirely 
wanting  in  districts  composed  of  argillaceous  and  sandy  formations,  which 
must,  nevertheless,  have  been  upheaved  at  the  same  time,  and  by  the  same 
intermittent  movements,  as  the  adjoining  calcareous  rocks. 


CHAPTER  VE. 

ALLUVIUM. 

Alluvium  described — Due  to  complicated  causes — Of  various  ages,  as  shown  in 
Auvergne — How  distinguished  from  rocks  in  situ — River-terraces — Parallel 
roads  of  Glen  Roy — Various  theories  respecting  their  origin. 

BETWEEN  the  superficial  covering  of  vegetable  mould  and  the  subjacent 
rock  there  usually  intervenes  in  every  district  a  deposit  of  loose  gravel, 
sand,  and  mud,  to  which  the  name  of  alluvium  has  been  applied.  The 
term  is  derived  from  alluvio,  an  inundation,  or  alluo,  to  wash,  because  the 
pebbles  and  sand  commonly  resemble  those  of  a  river's  bed  or  the  mud 
and  gravel  washed  over  low  lands  by  a  flood. 

A  partial  covering  of  such  alluvium  is  found  alike  in  all  climates,  from 
the  equatorial  to  the  polar  regions ;  but  in  the  higher  latitudes  of  Europe 
and  North  America  it  assumes  a  distinct  character,  being  very  frequently 
devoid  of  stratification,  and  containing  huge  fragments  of  rock,  some  an- 
gular and  others  rounded,  which  have  been  transported  to  great  distances 
from  their  parent  mountains.  When  it  presents  itself  in  this  form,  it  has 
been  called  "  diluvium,"  "  drift,"  or  the  "  boulder  formation ;"  and  its  prob- 


80 


ALLUVIUM   IN  AUVERGNE. 


[Ca  VII. 


able  connection  with  the  agency  of  floating  ice  and  glaciers  will  be  treated 
of  more  particularly  in  the  eleventh  and  twelfth  chapters. 

The  student  will  be  prepared,  by  what  I  have  said  in  the  last  chaptei 
on  denudation,  to  hear  that  loose  gravel  and  sand  are  often  met  with, 
not  only  on  the  low  grounds  bordering  rivers,  but  also  at  various  points 
on  the  sides  or  even  summits  of  mountains.  For,  in  the  course  of  those 
changes  in  physical  geography  which  may  take  place  during  the  gradual 
emergence  of  the  bottom  of  the  sea  and.  its  conversion  into  diy  land, 
any  spot  may  either  have  been  a  sunken  reef,  or  a  bay,  or  estuary,  or 
sea-shore,  or  the  bed  of  a  river.  The  drainage,  moreover,  may  have  been 
deranged  again  and  again  by  earthquakes,  during  which  temporary  lakes 
are  caused  by  landslips,  and  partial  deluges  occasioned  by  the  bursting 
of  the  barriers  of  such  lakes.  For  this  reason  it  would  be  unreason- 
able to  hope  that  we  should  ever  be  able  to  account  for  all  the  alluvial 
phenomena  of  each  particular  country,  seeing  that  the  causes  of  their 
origin  are  so  various.  Besides,  the  last  operations  of  water  have  a 
tendency  to  disturb  and  confound  together  all  pre-existing  alluviums. 
Hence  we  are  always  in  danger  of  regarding  as  the  work  of  a  single 
era,  and  the  effect  of  one  cause,  what  has  in  reality  been  the  result  of  a 
variety  of  distinct  agents,  during  a  long  succession  of  geological  epochs. 
Much  useful  instruction  may  therefore  be  gained  from  the  exploration  of 
a  country  like  Auvergne,  where  the  superficial  gravel  of  very  different 
eras  happens  to  have  been  preserved  by  sheets  of  lava,  which  were 
poured  out  one  after  the  other  at  periods  when  the  denudation,  and 
probably  the  upheaval,  of  rocks  were  in  progress.  That  region  had  al- 
ready acquired  in  some  degree  its  present  configuration  before  any  volca- 
noes were  in  activity,  and  before  any  igneous  matter  was  superimposed 
upon  the  granitic  and  fossiliferous  formations.  The  pebbles  therefore  in 
the  older  gravels  are  exclusively  constituted  of  granite  and  other  aborigi- 
nal rocks ;  and  afterwards,  when  volcanic  vents  burst  forth  into  eruption, 


Fig.  99. 


Lavas  of  Auvergne  resting  on  alluviums  of  different  ages. 

those  earlier  alluviums  were  covered  by  streams  of  lava,  which  protected 
them  from  intermixture  with  gravel  of  subsequent  date.  In  the  course 
of  ages,  a  new  system  of  valleys  was  excavated,  so  that  the  rivers  ran 
at  lower  levels  than  those  at  which  the  first  alluviums  and  sheets  of  lava 
were  formed.  When,  therefore,  fresh  eruptions  gave  rise  to  new  lava, 
the  melted  matter  was  poured  out  over  lower  grounds ;  and  the  gravel 


CH.  VII] 


ALLUVIUM. 


81 


of  these  plains  differed  from  the  first  or  upland  alluvium,  by  containing 
in  it  rounded  fragments  of  various  volcanic  rocks,  and  often  bones  be- 
longing to  distinct  groups  of  land  animals  which  flourished  in  the  country 
in  succession. 

The  annexed  drawing  will  explain  the  different  heights  at  which  beds  of 
lava  and  gravel,  each  distinct  from  the  other  in  composition  and  age,  are 
observed,  some  on  the  flat  tops  of  hills,  TOO  or  800  feet  high,  others  on 
the  slope  of  the  same  hills,  and  the  newest  of  all  in  the  channel  of  the 
existing  river  where  there  is  usually  gravel  alone,  but  in  some  cases  a  nar- 
row stripe  of  solid  lava  sharing  the  bottom  of  the  valley  with  the  river. 
In  all  these  accumulations  of  transported  matter  of  different  ages,  the  bones 
of  extinct  mammalia  have  been  found  belonging  to  assemblages  of  land 
quadrupeds  which  flourished  in  the  country  in  succession,  and  which 
vary  specifically,  the  one  set  from  the  other,  in  a  greater  or  less  degree, 
in  proportion  as  the  time  which  separated  their  entombment  has  been 
more  or  less  protracted.  The  streams  in  the  same  district  are  still  under- 
mining their  banks  and  grinding  down  into  pebbles  or  sand,  columns 
of  basalt  and  fragments  of  granite  and  gneiss;  but  portions  of  the 
older  alluviums,  with  the  fossil  remains  belonging  to  them,  are  prevented 
from  being  mingled  with  the  gravel  of  recent  date  by  the  cappings  of 
lava  before  mentioned.  But  for  the  accidental  interference,  therefore,  of 
this  peculiar  cause,  all  the  alluviums  might  have  passed  so  insensibly  the 
one  into  the  other,  that  those  formed  at  the  remotest  era  might  have 
appeared  of  the  same  date  as  the  newest,  and  the  whole  formation  might 
have  been  regarded  by  some  geologists  as  the  result  of  one  sudden  and 
violent  catastrophe. 

In  almost  every  country,  the  alluvium  consists  in  its  upper  part  of 
transported  materials,  but  it  often  passes  downwards  into  a  mass  of 
broken  and  angular  fragments  derived  from  the  subjacent  rock.  To  this 
mass  the  provincial  .name  of  "  rubble,"  or  "  brash,"  is  given  in  many 
parts  of  England.  It  may  be  referred  to  the  weathering  or  disintegra- 
tion of  stone  on  the  spot,  the  effects  of  air  and  water,  sun  and  frost,  and 
chemical  decomposition. 

The  inferior  surface  of  alluvial  deposits  is  often  very  irregular,  con- 
forming to  all  the  inequalities  of  the  fundamental  rocks  (fig.  100).  Oc- 
casionally, a  small  mass,  as  at  c,  appears 
detached,  and  as  if  included  in  the  subja- 
cent formation.  Such  isolated  portions  are 
usually  sections  of  winding  subterranean 
hollows  filled  up  with  alluvium.  They 
may  have  been  the  courses  of  springs  or 
subterranean  streamlets,  which  have  flowed 
through  and  enlarged  natural  rents ;  or, 
when  on  a  small  scale  and  in  soft  strata, 
they  may  be  spaces  which  the  roots  of  large 
trees  have  once  occupied,  gravel  and  sand 
ha-ving  been  introduced  after  their  decay. 


Fig.  100. 


a.  Vegetable  soil  ft.  Alluvium. 

c.  Mass  of  same,  apparently  detached. 


82  SAND-PIPES.  [CH.  VII 

But  there  are  other  deep  hollows  of  a  cylindrical  form  found  in  Eng- 
land, France,  and  elsewhere,  penetrating  the  white  chalk,  and  filled  with 
sand  and  gravel,  which  are  not  so  readily  explained.  They  are  some- 
times called  "sand-pipes,"  or  "sand-galls,"  and  "puits  naturels,"  in 
France.  Those  represented  in  the  annexed  cut  were  observed  by  me  in 

Fig.  101. 


Band-pipes  in  the  chalk  at  Eaton,  near  Norwich. 

1839,  laid  open  in  a  large  chalk-pit  near  Norwich.  They  were  of  very 
symmetrical  form,  the  largest  more  than  12  feet  in  diameter,  and  some 
of  them  had  been  traced,  by  boring,  to  the  depth  of  more  than  60  feet. 
The  smaller  ones  varied  from  a  few  inches  to  a  foot  in  diameter,  and 
seldom  descended  more  than  12  feet  below  the  surface.  Even  where 
three  ofthem  occurred,  as  at  a,  fig.  101,  very  close  together,  the  parting 
walls  of  soft  white  chalk  were  not  broken  through.  They  all  taper 
downwards  and  end  in  a  point.  As  a  general  rule,  sand  and  pebbles 
occupy  the  central  parts  of  each  pipe,  while  the  sides  and  bottom  are 
lined  with  clay. 

Mr.  Trimmer,  in  speaking  of  appearances  of  the  same  kind  in  the 
Kentish  chalk,  attributes  the  origin  of  such  "  sand-galls"  to  the  action 
of  the  sea  on  a  beach  or  shoal,  where  the  waves,  charged  with  shingle 
and  sand,  not  only  wear  out  longitudinal  furrows,  such  as  may  be  ob- 
served on  the  surface  of  the  above-mentioned  chalk  near  Norwich  when 
the  incumbent  gravel  is  removed,  but  also  drill  deep  circular  hollows  by 
the  rotatory  motion  imparted  to  sand  and  pebbles.  Such  furrows,  as  well 
as  vertical  cavities,  are  now  formed,  he  observes,  on  the  coast  where  the 
shores  are  composed  of  chalk.* 

That  the  commencement  of  many  of  the  tubular  cavities  now  under 
consideration  has  been  due  to  the  cause  here  assigned,  I  have  little  doubt 
But  such  mechanical  action  could  not  have  hollowed  out  the  whole  of 
the  sand-pipes  c  and  c?,  fig.  101,  because  several  large  chalk-flints  seen 
protruding  from  the  walls  of  the  pipes  have  not  been  eroded,  while  sand 
and  gravel  have  penetrated  many  feet  below  them.  In  other  cases,  as 

*  Trimmer,  Proceedings  of  Geol.  Soc.  vol.  iv.  p.  7,  1842. 


CH.  VII.]  ALLUVIUM.  83 

at  b  b,  similar  unrounded  nodules  of  flint,  still  preserving  their  irregular 
form  and  white  coating,  are  found  at  various  depths  in  the  midst  of  the 
loose  materials  filling  the  pipe.  These  have  evidently  been  detached 
from  regular  layers  of  flints  occurring  above.  It  is  also  to  be  remarked 
that  the  course  of  the  same  sand-pipe,  b  b,  is  traceable  above  the  level 
of  the  chalk  for  some  distance  upwards,  through  the  incumbent  gravel 
and  sand,  by  the  obliteration  of  all  signs  of  stratification.  Occasionally, 
also,  as  in  the  pipe  c?,  the  overlying  beds  of  gravel  bend  downwards  into 
the  mouth  of  the  pipe,  so  as  to  become  in  part  vertical,  as  would  happen 
if  horizontal  layers  had  sunk  gradually  in  consequence  of  a  failure  of 
support.  All  these  phenomena  may  be  accounted  for  by  attributing  the 
enlargement  and  deepening  of  the  sand-pipes  to  the  chemical  action  of 
water  charged  with  carbonic  acid,  derived  from  the  vegetable  soil  and 
the  decaying  roots  of  trees.  Such  acid  might  corrode  the  chalk,  >,*nd 
deepen  indefinitely  any  previously  existing  hollow,  but  could  not  dissolve 
the  flints.  The  water,  after  it  had  become  saturated  with  carbonate  of 
lime,  might  freely  percolate  the  surrounding  porous  walls  of  chalk,  and 
escape  through  them  and  from  the  bottom  of  the  tube,  so  as  to  carry 
away  in  the  course  of  time  large  masses  of  dissolved  calcareous  rock,* 
and  leave  behind  it  on  the  edges  of  each  tubular  hollow  a  coating  of  fine 
clay,  which  the  white  chalk  contains. 

I  have  seen  tubes  precisely  similar  and  from  1  to  5  feet  in  diameter 
traversing  vertically  the  upper  half  of  the  soft  calcareous  building-stone, 
or  chalk  without  flints,  constituting  St.  Peter's  Mount,  Maestricht.  These 
hollows  are  filled  with  pebbles  and  clay,  derived  from  overlying  beds  of 
gravel,  and  all  terminate  downwards  like  those  of  Norfolk.  I  was  in- 
formed that,  6  miles  from  Maestricht,  one  of  these  pipes,  2  feet  in  diam- 
eter, was  traced  downwards  to  a  bed  of  flattened  flints,  forming  an  almost 
continuous  layer  in  the  chalk.  Here  it  terminated  abruptly,  but  a  few 
small  root-like  prolongations  of  it  were  detected  immediately  below, 
probably  where  the  dissolving  substance  had  penetrated  at  some  points 
through  openings  in  the  siliceous  mass. 

It  is  not  so  easy  as  may  at  first  appear  to  draw  a  clear  line  of  distinc- 
tion between  the  fixed  rocks,  or  regular  strata  (rocks  in  situ  or  in  place), 
and  alluvium.  If  the  bed  of  a  torrent  or  river  be  dried  up,  we  call  the 
gravel,  sand,  and  mud  left  in  their  channels,  or  whatever,  during  floods, 
they  may  have  scattered  over  the  neighboring  plains,  alluvium.  The 
very  same  materials  carried  into  a  lake,  where  they  become  sorted  by 
water  and  arranged  in  more  distinct  layers,  especially  if  they  inclose  the 
remains  of  plants,  shells,  or  other  fossils,  are  termed  regular  strata. 

In  like  manner  we  may  sometimes  compare  the  gravel,  sand,  and 
broken  shells,  strewed  along  the  path  of  a  rapid  marine  current,  with  a 
deposit  formed  contemporaneously  by  the  discharge  of  similar  materials, 
year  after  year,  into  a  deeper  and  more  tranquil  part  of  the  sea.  In 
such  cases,  when  we  detect  marine  shells  or  other  organic  remains  en- 

*  See  Lyell  on  Sand-pipes,  Ac.  Phil.  Mag.  third  series,  voL  xv.  p.  257,  Oct.  1839. 


84:  ALLUVIUM.  [On.  VII 

tombed  in  the  strata,  which  enable  us  to  determine  their  age  and 
mode  of  origin,  we  regard  them  as  part  of  the  regular  series  of  fos- 
siliferous  formations,  whereas,  if  there  are  no  fossils,  we  have  frequently 
no  power  of  separating  them  from  the  general  mass  of  superficial  al- 
luvium. 

The  usual  rarity  of  organic  remains  in  beds  of  loose  gravel  is  partly 
owing  to  the  friction  which  originally  ground  down  rocks  into  pebbles  or 
sand,  and  organic  bodies  into  small  fragments,  and  it  is  partly  owing  to 
the  porous  nature  of  alluvium  when  it  has  emerged,  which  allows  the  free 
percolation  through  it  of  rain-water,  and  promotes  the  decomposition  and 
solution  of  fossil  remains. 

It  has  long  been  a  matter  of  common  observation  that  most  rivers 
are  now  cutting  their  channels  through  alluvial  deposits  of  greater  depth 
and  extent  than  could  ever  have  been  formed  by  the  present  streams. 
From  this  fact  a  rash  inference  has  sometimes  been  drawn,  that  rivers  in 
general  have  grown  smaller,  or  become  less  liable  to  be  flooded  than  for- 
merly. But  suah  phenomena  would  be  a  natural  result  of  considerable 
oscillations  in  the  level  of  the  land  experienced  since  the  existing  valleys 
originated. 

Suppose  part  of  a  continent,  comprising  within  it  a  large  hydrographical 
basin  like  that  of  the  Mississippi,  to  subside  several  inches  or  feet  in  a 
century,  as  the  west  coast  of  Greenland,  extending  600  miles  north  and 
south,  has  been  sinking  for  three  or  four  centuries,  between  the  latitudes 
60°  and  69°  N".*  It  will  rarely  happen  that  the  rate  of  subsidence  will 
be  everywhere  equal,  and  in  many  cases  the  amount  of  depression  in  the 
interior  will  regularly  exceed  that  of  the  region  nearer  the  sea.  Whenever 
this  happens,  the  fall  of  the  waters  flowing  from  the  upland  country  will 
be  diminished,  and  each  tributary  stream  will  have  less  power  to  cany  its 
sand  and  sediment  into  the  main  river,  and  the  main  river  less  power  to 
convey  its  annual  burden  of  transported  matter  to  the  sea.  All  the  rivers, 
therefore,  will  proceed  to  fill  up  partially  their  ancient  channels,  and, 
during  frequent  inundations,  will  raise  their  alluvial  plains  by  new  deposits. 
If  then  the  same  area  of  land  be  again  upheaved  to  its  former  height,  the 
fall,  and  consequently  the  velocity,  of  every  river  would  begin  to  aug- 
ment. Each  of  them  would  be  less  given  to  overflow  its  alluvial  plain  ; 
and  their  power  of  carrying  earthy  matter  seaward,  and  of  scouring  out 
and  deepening  their  channels,  will  be  sustained  till,  after  a  lapse  of  many 
thousand  years,  each  of  them  has  eroded  a  new  channel  or  valley  through 
a  fluviatile  formation  of  comparatively  modern  date.  The  surface  of  what 
was  once  the  river-plain  at  the  period  of  greatest  depression,  will  then 
remain  fringing  the  valley  sides  in  the  form  of  a  terrace  apparently  flat, 
but  in  reality  sloping  down  with  the  general  inclination  of  the  river. 
Everywhere  this  terrace  will  present  cliff's  of  gravel  and  sand,  facing 
the  river.  That  such  a  series  of  movements  has  actually  taken  place  in 
the  main  valley  of  the  Mississippi  and  in  its  tributary  valleys  during 

*  Principles  of  Geology,  7th  ed.  p.  506,  8th  ed.  p.  509. 


CH.  VIL] 


RIVER   TERRACES. 


85 


oscillations  of  level,  I  have  endeavored  to  show  in  my  description  of  that 
country;*  and  the  freshwater  shells  of  existing  species  and  bones  of 
land  quadrupeds,  partly  of  extinct  races  preserved  in  the  terraces  of  flu- 
viatile  origin,  attest  the  exclusion  of  the  sea  during  the  whole  process  of 
filling  up  and  partial  re-excavation. 

In  many  cases,  the  alluvium  in  which  rivers  are  now  cutting  their 
channels,  originated  when  the  land  first  rose  out  of  the  sea.  If,  for  ex- 
ample, the  emergence  was  caused  by  a  gradual  and  uniform  motion, 
every  bay  and  estuary,  or  the  straits  between  islands,  would  dry  up 
slowly,  and  during  their  conversion  into  valleys,  every  part  of  the  up- 
heaved area  would  in  its  turn  be  a  sea-shore,  and  inight  be  strewed  over 
with  littoral  sand  and  pebbles,  or  each  spot  might  be  the  point  where  a 
delta  accumulated  during  the  retreat  and  exclusion  of  the  sea.  Mate- 
rials so  accumulated  would  conform  to  the  general  slope  of  a  valley  from 
its  head  to  the  sea-coast. 

River  terraces. — We  often  observe  at  a  short  distance  from  the  present 
bed  of  a  river  a  steep  cliff  a  few  feet  or  yards  high,  and  on  a  level  with 
the  top  of  it  a  flat  terrace  corresponding  in  appearance  to  the  alluvial 
plain  which  immediately  borders  the  river.  This  terrace  is  again  bounded 
by  another  cliff,  above  which  a  second  terrace  sometimes  occurs :  and  in 
this  manner  two  or  three  ranges  of  cliffs  and  terraces  are  occasionally 
seen  on  one  or  both  sides  of  the  stream,  the  number  varying,  but  those 
on  the  opposite  sides  often  corresponding  in  height. 

Fig.  102. 


Eiver  Terraces  and  Parallel  Eoads. 

These  terraces  are  seldom  continuous  for  great  distances,  and  their 
surface  slopes  downwards,  with  an  inclination  similar  ta  that  of  the  river. 
They  are  readily  explained  if  we  adopt  the  hypothesis  before  suggested, 
of  a  gradual  rise  of  the  land  ;  especially  if,  while  rivers  are  shaping  out 
their  beds,  the  upheaving  movement  be  intermittent,  so  that  long  pauses 
shall  occur,  during  which  the  stream  will  have  time  to  encroach  upon 
one  of  its  banks,  so  as  to  clear  away  and  flatten  a  large  space.  This 

*  Second  Visit  to  the  U.  S,  vol.  ii.  chap.  34. 


86  PAEALLEL   KOADS  [On.  VII 

operation  being  afterwards  repeated  at  lower  levels,,  there  will  be  several 
successive  cliffs  and  terraces. 

Parallel  roads. — The  parallel  shelves,  or  roads,  as  they  have  been 
called,  of  Lochaber  or  Glen  Roy  and  other  contiguous  valleys  in  Scot- 
land, are  distinct  both  in  character  and  origin  from  the  terraces  above 
described  ;  for  they  have  no  slope  towards  the  sea  like  the  channel  of  a 
river,  nor  are  they  the  effect  of  denudation.  Glen  Roy  is  situated  in 
the  western  Highlands,  about  ten  miles  north  of  Fort  "William,  near  the 
western  end  of  the  great  glen  of  Scotland,  or  Caledonian  Canal,  and  near 
the  foot  of  the  highest  of  the  Grampians,  Ben  Nevis.  Throughout  its 
whole  length,  a  distance  of  more  than  ten  miles,  twc,  and  in  its  lower 
part  three,  parallel  roads  or  shelves  are  traced  along  the  steep  sides  of 
the  mountains,  as  represented  in  the  annexed  figure  (fig.  102),  each 
maintaining  a  perfect  •  horizontally,  and  continuing  at  exactly  the  same 
level  on  the  opposite  sides  of  the  glen.  Seen  at  a  distance,  they  appear 
like  ledges  or  roads,  cut  artificially  out  of  the  sides  of  the  hills ;  but 
when  we  are  upon  them  we  can  scarcely  recognize  their  existence,  so 
uneven  is  their  surface,  and  so  covered  with  boulders.  They  are  from 
10  to  60  feet  broad,  and  merely  differ  from  the  side  of  the  mountain  by 
being  somewhat  less  steep. 

On  closer  inspection,  we  find  that  these  terraces  are  stratified  in  the 
ordinary  manner  of  alluvial  or  littoral  deposits,  as  may  be  seen  at  those 
points  where  ravines  have  been  excavated  by  torrents.  The  parallel 
shelves,  therefore,  have  not  been  caused  by  denudation,  but  by  the  depo- 
sition of  detritus,  precisely  similar  to  that  which  is  dispersed  in  smaller 
quantities  over  the  declivities  of  the  hills  above.  These  hills  consist  of 
clay-slate,  mica-schist,  and  granite,  which  rocks  have  been  worn  away 
and  laid  bare  at  a  few  points  only,  in  a  line  just  above  the  parallel  roads. 
The  highest  of  these  roads  is  about  1250  feet  above  the  level  of  the  sea, 
the  next  about  200  feet  lower  than  the  uppermost,  and  the  third  still 
lower  by  about  50  feet.  It  is  only  this  last,  or  the  lowest  of  the  three, 
which  is  continued  throughout  Glen  Spean,  a  large  valley  with  which 
Glen  Roy  unites.  As  the  shelves  are  always  at  the  same  height  above 
the  sea,  they  become  continually  more  elevated  above  the  river  in  pro- 
portion as  we  descend  each  valley ;  and  they  at  length  terminate  very 
abruptly,,  without  any  obvious  cause,  or  any  change  either  in  the  shape 
of  the  ground,  or  in  the  composition  or  hardness  of  the  rocks.  I  should 
exceed  the  limits  of  this  work,  were  I  to  attempt  to  give  a  full  descrip- 
tion of  all  the  geographical  circumstances  attending  these  singular  ter- 
races, or  to  discuss  the  ingenious  theories  which  have  been  severally 
proposed  to  account  for  them  by  Dr.  MacCuiloch,  Sir  T.  D.  Lauder,  and 
Messrs.  Darwin,  Agassiz,  Milne,  and  Chambers.  There  is  one  point, 
however,  on  which  all  are  agreed,  namely,  that  these  shelves  are  ancient 
beaches,  or  littoral  formations  accumulated  round  the  edges  of  one  or 
more  sheets  of  water  which  once  stood  at  the  level,  first  of  the  highest 
shelf,  and  successively  at  the  height  of  the  two  others.  It  is  well  known, 
that  wherever  a  lake  or  marine  fiord  exists  surrounded  by  steep  moun- 


CH.  VII]  OF  GLEX   ROY.  87 

tains  subject  to  disintegration  by  frost  or  the  action  of  torrents,  some 
loose  matter  is  washed  down  annually,  especially  during  the  melting  of 
snow,  and  a  check  is  given  to  the  descent  of 
this  detritus  at  the  point  where  it  reaches 
the  waters  of  the  lake.  The  waves  then 
spread  out  the  materials  along  the  shore,  and 
throw  some  of  them  upon  the  beach  ;  their 
dispersing  power  being  aided  by  the  ice, 
which  often  adheres  to  pebbles  during  the 
winter  months,  and  gives  buoyancy  to  them. 
The  annexed  diagram  illustrates  the  manner 

~B  in  which  Dr.  MacCulloch  and  Mr.  Darwin 

A  RC  Supposed  original  surface  of      SUppOse  « the  roads"  to  constitute  mere  in- 
CD.  Roads  or  shelves  in  the  outer      dentations  in  a  superficial  alluvial  coating 

alluvial  covering  of  the  hill.  \  ,  .   ° 

which  rests  upon  the  hill-side,  and  consists 
chiefly  of  clay  and  sharp  unrounded  stones. 

Among  other  proofs  that  the  parallel  roads  have  really  been  formed 
along  the  margin  of  a  sheet  of  water,  it  may  be  mentioned,  that  wher- 
ever an  isolated  hill  rises  in  the  middle  of  the  glen  above  the  level  of 
any  particular  shelf,  a  corresponding  shelf  is  seen  at  the  tame  level 
passing  round  the  hill,  as  would  have  happened  if  it  had  once  formed  an 
island  in  a  lake  or  fiord.  Another  very  remarkable  peculiarity  in  these 
terraces  is  this  ;  each  of  them  comes  in  some  portion  of  its  course  to  a 
col,  or  passage  between  the  heads  of  glens,  the  explanation  of  which  will 
be  considered  in  the  sequel. 

Those  writers  who  first  advocated  the  doctrine  that  the  roads  were  the 
ancient  beaches  of  freshwater  lakes,  were  unable  to  offer  any  probable 
hypothesis  respecting  the  formation  and  subsequent  removal  of  barriers 
of  sufficient  height  and  solidity  to  dam  up  the  water.  To  introduce 
any  violent  convulsion  for  their  removal  was  inconsistent  with  the  unin- 
terrupted horizontality  of  the  roads,  and  with  the  undisturbed  aspect  of 
those  parts  of  the  glens  where  the  shelves  come  suddenly  to  an  end. 
Mr.  Agassiz  and  Dr.  Buckland,  desirous,  like  the  defenders  of  the  lake 
theory,  to  account  for  the  limitation  of  the  shelves  to  certain  glens,  and 
their  absence  in  contiguous  glens,  where  the  rocks  are  of  the  same  com- 
position, and  the  slope  and  inclination  of  the  ground  very  similar,  started 
the  conjecture  that  these  valleys  were  once  blocked  up  by  enormous  gla- 
ciers descending  from  Ben  JS"evis,  giving  rise  to  what  are  called  in  Swit- 
zerland and  in  the  Tyrol,  glacier-lakes.  After  a  time  the  icy  barrier 
was  broken  down,  or  melted,  first,  to  the  level  of  the  second,  and  after- 
wards to  that  of  the  third  road  or  shelf. 

In  corroboration  of  this  view,  they  contended  that  the  alluvium  of 
Glen  Roy,  as  well  as  of  other  parts  of  Scotland,  agrees  in  character  with 
the  moraines  of  glaciers  seen  in  the  Alpine  valleys  of  Switzerland.  Al- 
lusion will  be  made  in  the  eleventh  chapter  to  the  former  existence  of 
glaciers  in  the  Grampians :  in  the  mean  time  it  will  readily  be  conceded 
that  this  hypothesis  is  preferable  to  any  previous  lacustrine  theory,  by 


88  PARALLEL  ROADS  OF  GLEN  ROY.       [Cn.  VH 

accounting  more  easily  for  the  temporary  existence  and  entire  disappear* 
ance  of  lofty  transverse  barriers,  although  the  height  required  for  the  im- 
aginary dams  of  ice  may  be  startling. 

Before  the  idea  last  alluded  to  had  been  entertained,  Mr.  Darwin  examined 
Glen  Roy,  and  came  to  the  opinion  that  the  shelves  were  formed  when  the 
glens  were  still  arms  of  the  sea,  and  consequently,  that  there  never  were 
any  seaward  barriers.  According  to  him,  the  land  emerged  during  a  slow 
and  uniform  upward  movement,  like  that  now  experienced  throughout  a 
large  part  of  Sweden  and  Finland  ;  but  there  were  certain  pauses  in  the 
upheaving  process,  at  which  times  the  waters  of  the  sea  remained  station- 
ary for  so  many  centuries  as  to  allow  of  the  accumulation  of  an  extraor- 
dinary quantity  of  detrital  matter,  and  the  excavation,  at  many  points  im- 
mediately above,  of  deep  notches  and  bare  cliffs  in  the  hard  and  solid  rock. 

The  phenomena  which  are  most  difficult  to  reconcile  with  this  theory  are, 
first,  the  abrupt  cessation  of  the  roads  at  certain  points  in  the  different 
glens ;  secondly,  their  unequal  number  in  different  valleys  connecting  with 
each  other,  there  being  three,  for  example,  in  Glen  Roy  and  only  one  in 
Glen  Spean ;  thirdly,  the  precise  horizontality  of  level  maintained  by  the 
same  shelf  over  a  space  many  leagues  in  length  requiring  us  to  assume, 
that  during  a  rise  of  1250  feet  no  one  portion  of  the  land  was  raised  even 
a  few  yards  above  another ;  fourthly,  the  coincidence  of  level  already  al- 
luded to  of  each  shelf  with  a  col,  or  the  point  forming  the  head  of  two 
glens,  from  which  the  rain-waters  flow  in  opposite  directions.  This  last- 
mentioned  feature  in  the  physical  geography  of  Lochaber  seems  to  have 
been  explained  in  a  satisfactory  manner  by  Mr.  Darwin.  He  calls  these 
cols  "  landstraits,"  and  regards  them  as  having  been  anciently  sounds  or 
channels  between  islands.  He  points  out  that  there  is  a  tendency  in  such 
sounds  to  be  silted  up,  and  always  the  more  so  in  proportion  to  their  nar- 
rowness. In  a  chart  of  the  Falkland  Islands  by  Capt.  Sullivan,  R.  N.,  it 
appears  that  there  are  several  examples  there  of  straits  where  the  sound- 
ings diminish  regularly  towards  the  narrowest  part.  One  is  so  nearly  dry 
that  it  can  be  walked  over  at  low  water,  and  another,  no  longer  covered 
by  the  sea,  is  supposed  to  have  recently  dried  up  in  consequence  of  a 
small  alteration  in  the  relative  level  of  sea  and  land.  "  Similar  straits," 
observes  Mr.  Chambers,  "  hovering,  in  character,  between  sea  and  land, 
and  which  may  be  called  fords,  are  met  with  in  the  Hebrides.  Such,  for 
example,  is  the  passage  dividing  the  islands  of  Lewis  and  Harris,  and  that 
between  North  Uist  and  Benbecula,  both  of  which  would  undoubtedly 
appear  as  cols,  coinciding  with  a  terrace  or  raised  beach,  all  round  tho 
islands,  if  the  sea  were  to  subside."* 

The  first  of  the  difficulties  above  alluded  to,  namely,  the  non-extension 
of  the  shelves  over  certain  parts  of  the  glens,  may  be  explained,  as  Mr. 
Darwin  suggests,  by  supposing  in  certain  places  a  quick  growth  of  green 
turf  on  a  good  soil,  which  prevented  the  rain  from  washing  away  any  loose 
materials  lying  on  the  surface.  But  wherever  the  soil  was  barren,  and  where 
green  sward  took  long  to  form,  there  may  have  been  time  for  the  removal  of 

*  "  Ancient  Sea  Margins,"  p.  114,  by  R.  Chambers. 


CH.  VI1L]  CHRONOLOGY  OF  ROCKS.  89 

the  gravel.  In  one  case  an  intermediate  shelf  appears  for  a  short  distance 
(three  quarters  of  a  mile)  on  the  face  of  the  mountain  called  Tombhran, 
between  the  two  upper  shelves,  and  is  seen  nowhere  else.  It  occurs  where 
there  was  the  longest  space  of  open  water,  and  where,  perhaps,  the  waves 
acquired  a  greater  than  ordinary  power  in  heaping  up  detritus. 

Next  as  to  the  precise  horizontality  of  level  maintained  by  the  parallel 
roads  of  Lochaber  over  an  area  many  leagues  in  length  and  breadth,  this 
is  a  difficulty  common  in  some  degree  to  all  the  rival  hypotheses,  whether 
of  lakes  or  glaciers,  or  of  the  simple  upheaval  of  the  land  above  the  sea. 
For  we  cannot  suppose  the  roads  to  be  more  ancient  than  the  glacial 
period,  or  the  era  of  the  boulder  formation  of  Scotland,  of  which  I  shall 
speak  in  the  eleventh  and  twelfth  chapters.  Strata  of  that  era  of  marine 
origin  containing  northern  shells  of  existing  species  have  been  found  at 
various  heights  in  Scotland,  some  on  the  east  and  others  on  the  west 
coast,  from  20  to  400  feet  high ;  and  in  one  region  in  Lanarkshire  not 
less  than  524  feet  above  high-water  mark.  It  seems,  therefore,  in  the 
highest  degree  improbable  that  Glen  Roy  should  have  escaped  entirely 
the  upward  movement  experienced  in  so  many  surrounding  regions, — a 
movement  implied  by  the  position  of  these  marine  deposits,  in  which  the 
shells  are  almost  all  of  known  recent  species.  But  if  the  motion  has 
really  extended  to  Glen  Roy  and  the  contiguous  glens,  it  must  have  up- 
lifted them  bodily,  without  in  the  slightest  degree  affecting  their  horizon- 
tality ;  and  this  being  admitted,  the  principal  objection  to  the  theory  of 
marine  beaches,  founded  on  the  uniformity  of  upheaval,  is  removed,  or  is 
at  least  common  to  every  theory  hitherto  proposed. 

To  assume  that  the  ocean  has  gone  down  from  the  level  of  the  upper- 
most shelf,  or  1250  feet,  simultaneously  all  over  the  globe,  while  the  land 
remained  unmoved,  is  a  view  which  will  find  favor  with  very  few  geolo- 
gists, for  the  reasons  explained  in  the  fifth  chapter. 

The  student  will  perceive,  from  the  above  sketch  of  the  controversy  re- 
specting the  formation  of  these  curious  shelves,  that  this  problem,  like  many 
others  in  geology,  is  as  yet  only  solved  in  part ;  and  that  a  larger  number 
of  facts  must  be  collected  and  reasoned  upon  before  the  question  can  be 
finally  settled. 


CHAPTER  VIII. 

CHRONOLOGICAL    CLASSIFICATION    OF    ROCKS. 

Aqueous,  plutonic,  volcanic,  and  metamorphic  rocks,  considered  chronologically — 
Lehman's  division  into  primitive  and  secondary — Werner's  addition  of  a  tran- 
sition class — Xeptunian  theory — Hutton  on  igneous  origin  of  granite — How  the 
name  of  primary  was  still  retained  for  granite — The  term  "  transition,"  why 
faulty — The  adherence  to  the  old  chronological  nomenclature  retarded  the 
progress  of  geology— New  hypothesis  intended  to  reconcile  the  igneous  origin 
of  granite  to  the  notion  of  its  high  antiquity — Explanation  of  the  chronological 
nomenclature  adopted  in  this  work,  so  far  as  regards  primary,  secondary,  and 
tertiary  periods. 


9Q  CLASSIFICATION  OF  KOCKS.  [On.  VIII 

IN  the  first  chapter  it  was  stated  that  the  four  great  classes  of  locks,  the 
aqueous,  the  volcanic,  the  plutonic,  and  the  metamorphic,  would  each  be 
considered  not  only  in  reference  to  their  mineral  characters,  and  mode  of  ori- 
gin, but  also  to  their  relative  age.  In  regard  to  the  aqueous  rocks,  we  have 
already  seen  that  they  are  stratified,  that  some  are  calcareous,  others  argil- 
laceous or  siliceous,  some  made  up  of  sand,  others  of  pebbles  ;  that  some 
contain  freshwater,  others  marine  fossils,  and  so  forth  ;  but  the  student  has 
still  to  learn  which  rocks,  exhibiting  some  or  all  of  these  characters,  have 
originated  at  one  period  of  the  earth's  history,  and  which  at  another. 

To  determine  this  point  in  reference  to  the  fossiliferous  formations  is 
more  easy  than  in  any  other  class,  and  it  is  therefore  the  most  convenient 
and  natural  method  to  begin  by  establishing  a  chronology  for  these  strata, 
and  then  to  refer  as  far  as  possible  to  the  same  divisions  the  several  groups 
of  plutonic,  volcanic,  and  metamorphic  rocks.  Such  a  system  of  classifica- 
tion is  not  only  recommended  by  its  greater  clearness  and  facility  of  ap- 
plication, but  is  also  best  fitted  to  strike  the  imagination  by  bringing  into 
one  view  the  contemporaneous  revolutions  of  the  inorganic  and  organic 
creations  of  former  times.  For  the  sedimentary  formations  are  most  readily 
distinguished  by  the  different  species  of  fossil  animals  and  plants  which 
they  inclose,  and  of  which  one  assemblage  after  another  has  flourished  and 
then  disappeared  from  the  earth  in  succession. 

But  before  entering  specially  on  the  subdivisions  of  the  aqueous  rocks 
arranged  according  to  the  order  of  time,  it  will  be  desirable  to  say  a  few 
words  on  the  chronology  of  rocks  in  general,  although  in  doing  so  we 
shall  be  unavoidably  led  to  allude  to  some  classes  of  phenomena  which 
the  beginner  must  not  yet  expect  fully  to  comprehend. 

It  was  for  many  years  a  received  opinion,  that  the  formation  of  entire 
families  of  rocks,  such  as  the  plutonic  and  those  crystalline  schists  spoken 
of  in  the  first  chapter  as  metamorphic,  began  and  ended  before  any  mem- 
bers of  the  aqueous  and  volcanic  orders  were  produced ;  and  although 
this  idea  has  long  been  modified,  and  is  nearly  exploded,  it  will  be  neces- 
sary to  give  some  account  of  the  ancient  doctrine,  in  order  that  beginners 
may  understand  whence  many  prevailing  opinions,  and  some  part  of  the 
nomenclature  of  geology,  still  partially  in  use,  was  derived. 

About  the  middle  of  the  last  century,  Lehman,  a  German  miner,  pro- 
posed to  divide  rocks  into  three  classes,  the  first  and  oldest  to  be  called 
primitive,  comprising  the  hypogene,  or  plutonic  and  metamorphic  rocks ; 
the  next  to  be  termed  secondary,  comprehending  the  aqueous  or  fossilif- 
erous strata ;  and  the  remainder,  or  third  class,  corresponding  to  our 
alluvium,  ancient  and  modern,  which  he  referred  to  "  local  floods,  and 
the  deluge  of  Noah."  In  the  primitive  class,  he  said;  such  as  granite 
and  gneiss,  there  are  no  organic  remains,  nor  any  signs  of  materials  de- 
rived from  the  ruins  of  pre-existing  rocks.  Their  origin,  therefore,  may 
have  been  purely  chemical,  antecedent  to  the  creation  of  living  beings, 
and  probably  coeval  with  the  birth  of  the  world  itself.  The  secondary 
formations,  on  the  contrary,  which  often  contain  sand,  pebbles,  and  or- 
ganic remains,  must  have  been  mechanical  deposits,  produced  after  the 


CH.  VIII.]  NEPTUNIAN   THEOKY.  91 

planet  had  become  the  habitation  of  animals  and  plants.  This  bold 
generalization,  although  anticipated  in  some  measure  by  Steno,  a  century 
before,  in  Italy,  formed  at  the  time  an  important  step  in  the  progress  of 
geology,  and  sketched  out  correctly  some  of  the  leading  divisions  into 
.which  rocks  may  be  separated.  About  half  a  century  later,  Werner,  so 
justly  celebrated  for  his  improved  methods  of  discriminating  the  minera- 
logical  characters  of  rocks,  attempted  to  improve  Lehman's  classification, 
and  with  this  view  intercalated  a  class,  called  by  him  "  the  transition 
formations,"  between  the  primitive  and  secondary.  Between  these  last 
he  had  discovered,  in  northern  Germany,  a  series  of  strata,  which  in  their 
mineral  peculiarities  were  of  an  intermediate  character,  partaking  in 
some  degree  of  the  crystalline  nature  of  micaceous  schist  and  clay-slate, 
and  yet  exhibiting  here  and  there  signs  of  a  mechanical  origin  and  or- 
ganic remains.  For  this  group,  therefore,  forming  a  passage  between 
Lehman's  primitive  and  secondary  rocks,  the  name  of  ubergang  or  transi- 
tion was  proposed.  They  consisted  principally  of  clay-slate  and  an  ar- 
gillaceous sandstone,  called  grauwacke,  and  partly  of  calcareous  beds. 
It  happened  in  the  district  which  Werner  first  investigated,  that  both  the 
primitive  and  transition  strata  were  highly  inclined,  while  the  beds  of 
the  newer  fossiliferous  rocks,  the  secondary  of  Lehman,  were  horizontal. 
To  these  latter  therefore,  he  gave  the  name  of  flbtz,  or  "  a  level  floor ;" 
and  every  deposit  more  modern  than  the  chalk,  which  was  classed  as  the 
uppermost  of  the  flotz  series,  was  designated  "  the  overflowed  land,"  an 
expression  which  may  be  regarded  as  equivalent  to  alluvium,  although 
under  this  appellation  were  confounded  all  the  strata  afterwards  called 
tertiary,  of  which  Werner  had  scarcely  any  knowledge.  As  the  followers 
of  Werner  soon  discovered  that  the  inclined  position  of  the  "  transition 
oeds,"  and  the  horizontality  of  the  flotz,  or  newer  fossiliferous  strata,  were 
mere  local  accidents,  they  soon  abandoned  the  term  flotz ;  and  the  four 
divisions  of  the  Wernerian  school  were  then  named  primitive,  transition, 
secondary,  and  alluvial. 

As  to  the  trappean  rocks,  although  their  igneous  origin  had  been  al- 
ready demonstrated  by  Arduino,  Fortis,  Faujas,  and  others,  and  especially 
by  Desmarest,  they  were  all  regarded  by  Werner  as  aqueous,  and  as  mere 
subordinate  members  of  the  secondary  series.* 

The  theory  of  Werner's  was  called  the  "  Neptunian."  and  for  many 
years  enjoyed  much  popularity.  It  assumed  that  the  globe  had  been  at 
first  invested  by  a  universal  chaotic  ocean,  holding  the  materials  of  all 
rocks  in  solution.  From  the  waters  of  this  ocean,  granite,  gneiss,  and 
other  crystalline  formations,  were  first  precipitated ;  and  afterwards,  when 
the  waters  were  purged  of  these  ingredients,  and  more  nearly  resembled 
those  of  our  actual  seas,  the  transition  strata  were  deposited.  These  were 
of  a  mixed  character,  not  purely  chemical,  because  the  waves  and  currents 
had  already  begun  to  wear  down  solid  land,  and  to  give  rise  to  pebbles, 
sand,  and  mud ;  nor  entirely  without  fossils,  because  a  few  of  the  first 
marine  animals  had  begun  to  exist.  After  this  period,  the  secondary  for- 
*  See  Principles  of  Geology,  vol.  i.  chap.  iv. 


92  ON  THE  TERM  "  TRANSITION."  [Cn.  Vlll 

mations  were  accumulated  in  waters  resembling  those  of  the  present  ocean, 
except  at  certain  intervals,  when,  from  causes  wholly  unexplained,  a  par- 
tial recurrence  of  the  "  chaotic  fluid"  took  place,  during  which  various 
trap  rocks,  some  highly  crystalline,  were  formed.  This  arbitrary  hypothe- 
sis rejected  all  intervention  of  igneous  agency,  volcanoes  being  regarded 
as  modern,  partial,  and  superficial  accidents,  of  trifling  account  among  the 
great  causes  which  have  modified  the  external  structure  of  the  globe. 

Meanwhile  Hutton,  a  contemporary  of  Werner,  began  to  teach,  in 
Scotland,  that  granite  as  well  as  trap  was  of  igneous  origin,  and  had  at 
various  periods  intruded  itself  in  a  fluid  state  into  different  parts  of  the 
earth's  crust.  He  recognized  and  faithfully  described  many  of  the  phe- 
nomena of  granitic  veins,  and  the  alterations  produced  by  them  on  the 
invaded  strata,  which  will  be  treated  of  in  the  thirty-third  chapter.  He, 
moreover,  advanced  the  opinion,  that  the  crystalline  strata  called  primi- 
tive had  not  been  precipitated  from  a  primaeval  ocean,  but  were  sediment- 
ary strata  altered  by  heat.  In  his  writings,  therefore,  and  in  those  of  his 
illustrator,  Playfair,  we  find  the  germ  of  that  metamorphic  theory  which 
has  been  already  hinted  at  in  the  first  chapter,  and  which  will  be  more 
fully  expounded  in  the  thirty -fourth  and  thirty-fifth  chapters. 

At  length,  after  much  controversy,  the  doctrine  of  the  igneous  origin  of 
trap  and  granite  made  its  way  into  general  favor ;  but  although  it  was,  in 
consequence,  admitted  that  both  granite  and  trap  had  been  produced  at 
many  successive  periods,  the  term  primitive  or  primary  still  continued  to 
be  applied  to  the  crystalline  formations  in  general,  whether  stratified,  like 
gneiss,  or  unstratified,  like  granite.  The  pupil  was  told  that  granite  was 
a  primary  rock,  but  that  some  granites  were  newer  than  certain  secondary 
formations  ;  and  in  conformity  with  the  spirit  of  the  ancient  language,  to 
which  the  teacher  was  still  determined  to  adhere,  a  desire  was  naturally 
engendered  of  extenuating  the  importance  of  those  more  modern  granites, 
the  true  dates  of  which  new  observations  were  continually  bringing  to  light. 

A  no  less  decided  inclination  was  shown  to  persist  in  the  use  of  the 
term  "  transition,"  after  it  had  been  proved  to  be  almost  as  faulty  in  its 
original  application  as  that  of  flotz.  The  name  of  transition,  as  already 
stated,  was  first  given  by  Werner,  to  designate  a  mineral  character,  inter- 
mediate between  the  highly  crystalline  or  metamorphic  state  and  that  of 
an  ordinary  fossiliferous  rock.  But  the  term  acquired  also  from  the  first 
a  chronological  import,  because  it  had  been  appropriated  to  sedimentary 
formations,  which,  in  the  Hartz  and  other  parts  of  Germany,  were  more 
ancient  than  the  oldest  of  the  secondary  series,  and  were  characterized  by 
peculiar  fossil  zoophytes  and  shells.  When,  therefore,  geologists  found 
in  other  districts  stratified  rocks  occupying  the  same  position,  and  inclosing 
similar  fossils,  they  gave  to  them  also  the  name  of  transition,  according 
to  rules  which  will  be  explained  in  the  next  chapter ;  yet,  in  many  cases, 
such  rocks  were  found  not  to  exhibit  the  same  mineral  texture  which 
Werner  had  called  transition.  On  the  contrary,  many  of  them  were  not 
more  crystalline  than  different  members  of  the  secondary  class ;  while, 
on  the  other  hand,  these  last  were  sometimes  found  to  assume  a  semi- 


CH.  VIIL]  CHANGES  OF  NOMENCLATURE.  93 

crystalline  and  almost  metamorphic  aspect,  and  thus,  on  lithological 
grounds,  to  deserve  equally  the  name  of  transition.  So  remarkably  was 
this  the  case  in  the  Swiss  Alps,  that  certain  rocks,  which  had  for  years 
been  regarded  by  some  of  the  most  skilful  disciples  of  Werner  to  be  tran- 
sition, were  at  last  acknowledged,  when  their  relative  position  and  fossils 
were  better  understood,  to  belong  to  the  newest  of  the  secondary  groups ; 
nay,  some  of  them  have  actually  been  discovered  to  be  members  of  the 
lower  tertiary  series  !  If,  under  such  circumstances,  the  name  of  transition 
was  retained,  it  is  clear  that  it  ought  to  have  been  applied  without  refer- 
ence to  the  age  of  strata,  and  simply  as  expressive  of  a  mineral  peculiarity. 
The  continued  appropriation  of  the  term  to  formations  of  a  given  date,  in- 
duced geologists  to  go  on  believing  that  the  ancient  strata  so  designated 
bore  a  less  resemblance  to  the  secondary  than  is  really  the  case,  and  to 
imagine  that  these  last  never  pass,  as  they  frequently  do,  into  metamor- 
phic rocks. 

The  poet  Waller,  when  lamenting  over  the  antiquated  style  of  Chaucer, 
complains  that — 

We  write  in  sand,  our  language  grows, 

And,  like  the  tide,  onr  work  o'erflowa. 

But  the  reverse  is  true  in  geology ;  for  here  it  is  our  work  which  contin- 
ually outgrows  the  language.  The  tide  of  observation  advances  with  such 
speed  that  improvements  in  theory  outrun  the  changes  of  nomenclature  ; 
and  the  attempt  to  inculcate  new  truths  by  words  invented  to  express  a 
different  or  opposite  opinion,  tends  constantly,  by  the  force  of  association 
to  perpetuate  error ;  so  that  dogmas  renounced  by  the  reason  still  retain 
a  strong  hold  upon  the  imagination. 

In  order  to  reconcile  the  old  chronological  views  with  the  new  doctrine 
of  the  igneous  origin  of  granite,  the  following  hypothesis  was  substituted 
for  that  of  the  Neptunists.  Instead  of  beginning  with  an  aqueous  men- 
struum or  chaotic  fluid,  the  materials  of  the  present  crust  of  the  earth 
were  supposed  to  have  been  at  first  in  a  state  of  igneous  fusion,  until  part 
of  the  heat  having  been  diffused  into  surrounding  space,  the  surface  of  the 
fluid  consolidated,  and  formed  a  crust  of  granite.  This  covering  of  crys- 
talline stone,  which  afterwards  grew  thicker  and  thicker  as  it  cooled,  was 
so  hot,  at  first,  that  no  water  could  exist  upon  it ;  but  as  the  refrigeration 
proceeded,  the  aqueous  vapor  in  the  atmosphere  was  condensed,  and,  fall- 
ing in  rain,  gave  rise  to  the  first  thermal  ocean.  So  high  was  the  tem- 
perature of  this  boiling  sea,  that  no  aquatic  beings  could  inhabit  its  waters, 
and  its  deposits  were  not  only  devoid  of  fossils,  but,  like  those  of  some 
hot  springs,  were  highly  crystalline.  Hence  the  origin  of  the  primary  or 
crystalline  strata, — gneiss,  mica-schist,  and  the  rest. 

Afterwards,  when  the  granitic  crust  had  been  partially  broken  up,  land 
and  mountains  began  to  rise  above  the  waters,  and  rains  and  torrents  to 
grind  down  rock,  so  that  sediment  was  spread  over  the  bottom  of  the 
seas.  Yet  the  heat  still  remaining  in  the  solid  supporting  substances 
was  sufficient  to  increase  the  chemical  action  exerted  by  the  water,  al- 
though not  so  intense  as  to  prevent  the  introduction  and  increase  of  some 


94  CHRONOLOGICAL   ARRANGEMENT  [Ca  VIII. 

living  beings.  During  this  state  of  things  some  of  the  residuary  mineral 
ingredients  of  the  primaeval  ocean  were  precipitated,  and  formed  deposits 
(the  transition  strata  of  Werner),  half  chemical  and  half  mechanical,  and 
containing  a  few  fossils. 

By  this  new  theory,  which  was  in  part  a  revival  of  the  doctrine  of 
Leibnitz,  published  in  1680,  on  the  igneous  origin  of  the  planet,  the  old 
ideas  respecting  the  priority  of  all  crystalline  rocks  to  the  creation  of  or- 
ganic beings,  were  still  preserved  ;  and  the  mistaken  notion  that  all  the 
semi-crystalline  and  partially  fossiliferous  rc>cks  belonged  to  one  period, 
while  all  the  earthy  and  uncrystalline  formations  originated  at  a  subse- 
quent epoch,  was  also  perpetuated. 

It  may  or  may  not  be  true,  as  the  great  Leibnitz  imagined,  that  the 
whole  planet  was  once  in  a  state  of  liquefaction  by  heat ;  but  there  are  cer- 
tainly no  geological  proofs  that  the  granite  which  constitutes  the  founda- 
tion of  so  much  of  the  earth's  crust  was  ever  at  once  in  a  state  of  universal 
fusion.  On  the  contrary,  all  our  evidence  tends  to  show  that  the  formation 
of  granite,  like  the  deposition  of  the  stratified  rocks,  has  been  successive, 
and  that  different  portions  of  granite  have  been  in  a  melted  state  at  dis- 
tinct and  often  distant  periods.  One  mass  was  solid,  and  had  been  frac- 
tured, before  another  body  of  granitic  matter  was  injected  into  it,  or  through 
it,  in  the  form  of  veins.  Some  granites  are  more  ancient  than  any  known 
fossiliferous  rocks ;  others  are  of  secondary ;  and  some,  such  as  that  of 
Mont  Blanc  and  part  of  the  central  axis  of  the  Alps,  of  tertiary  origin. 
In  short,  the  universal  fluidity  of  the  crystalline  foundations  of  the  earth's 
crust,  can  only  be  understood  in  the  same  sense  as  the  universality  of  the 
ancient  ocean.  All  the  land  has  been  under  water,  but  not  all  at  one 
time  ;  so  all  the  subterranean  unstratified  rocks  to  which  man  can  obtain 
access  have  been  melted,  but  not  simultaneously. 

In  the  present  work  the  four  great  classes  of  rocks,  the  aqueous,  plutonic, 
volcanic,  aiid  metamorphic,  will  form  four  parallel,  or  nearly  parallel,  col- 
umns in  one  chronological  table.  They  will  be  considered  as  four  sets  of 
monuments  relating  to  four  contemporaneous,  or  nearly  contemporaneous, 
series  of  events.  I  shall  endeavor,  in  a  subsequent  chapter  on  the  plutonic 
rocks,  to  explain  the  manner  in  which  certain  masses  belonging  to  each 
of  the  four  classes  of  rocks  may  have  originated  simultaneously  at  every 
geological  period,  and  how  the  earth's  crust  may  have  been  continually 
modelled,  above  and  below,  by  aqueous  and  igneous  causes,  from  times 
indefinitely  remote.  In  the  same  manner  as  aqueous  and  fossiliferous 
strata  are  now  formed  in  certain  seas  or  lakes,  while  in  other  places  vol- 
canic rocks  break  out  at  the  surface,  and  are  connected  with  reservoirs  of 
melted  matter  at  vast  depths  in  the  bowels  of  the  earth, — so,  at  every 
era  of  the  past,  fossiliferous  deposits  and  superficial  igneous  rocks  were  in 
progress  contemporaneously  with  others  of  subterranean  and  plutonic  ori- 
gin, and  some  sedimentary  strata  were  exposed  to  heat  and  made  to  as- 
sume a  crystalline  or  metamorphic  structure. 

It  can  by  no  means  be  taken  for  granted,  that  during  all  these  changes 
the  solid  crust  of  the  earth  has  been  increasing  in  thickness.  It  has  been 


Ca  VIII]  OF  KOCKS  IN  GENERAL.  95 

shown,  that  so  far  as  aqueous  action  is  concerned,  the  gain  by  fresh  deposits, 
and  the  loss  by  denudation,  must  at  each  period  have  been  equal  (see  above, 
p.  68) :  and  in  like  manner,  in  the  inferior  portion  of  the  earth's  crust,  the 
acquisition  of  new  crystalline  rocks,  at  each  successive  era,  may  merely  have 
counterbalanced  the  loss  sustained  by  the  melting  of  materials  previously 
consolidated.  As  to  the  relative  antiquity  of  the  crystalline  foundations  of 
the  earth's  crust,  when  compared  to  the  fossiliferous  and  volcanic  rocks 
which  they  support,  I  have  already  stated,  in  the  first  chapter,  that  to  pro- 
nounce an  opinion  on  this  matter  is  as  difficult  as  at  once  to  decide  which 
of  the  two,  whether  the  foundations  or  superstructure  of  an  ancient  city  built 
on  wooden  piles,  may  be  the  oldest.  We  have  seen  that,  to  answer  this 
question,  we  must  first  be  prepared  to  say  whether  the  work  of  decay  and 
restoration  had  gone  on  most  rapidly  above  or  below,  whether  the  average 
duration  of  the  piles  has  exceeded  that  of  the  stone  buildings,  or  the  contrary. 
So  also  in  regard  to  the  relative  age  of  the  superior  and  inferior  portions 
of  the  earth's  crust ;  we  cannot  hazard  even  a  conjecture  on  this  point,  un- 
til we  know  whether,  upon  an  average,  the  power  of  water  above,  or  that 
of  heat  below,  is  most  efficacious  in  giving  new  forms  to  solid  matter. 

After  the  observations  which  have  now  been  made,  the  reader  will  per- 
ceive that  the  term  primary  must  either  be  entirely  renounced,  or,  if  re- 
tained, must  be  differently  defined,  and  not  made  to  designate  a  set  of 
crystalline  rocks,  some  of  which  are  already  ascertained  to  be  newer  than 
all  the  secondary  formations.  In  this  work  I  shall  follow  most  nearly 
the  method  proposed  by  Mr.  Boue,  who  has  called  all  fossiliferous  rocks 
older  than  the  secondary  by  the  name  of  primary.  To  prevent  con- 
fusion, I  shall  sometimes  speak  of  these  last  as  the  primary  fossiliferous 
formations,  because  the  word  primary  has  hitherto  been  most  generally 
connected  with  the  idea  of  a  non-fossiliferous  rock.  Some  geologists,  to 
avoid  misapprehension,  have  introduced  the  term  Paleozoic  for  primary, 
from  -jraXcuov,  "  ancient,"  and  £wov,  "  an  organic  being,"  still  retaining  the 
terms  secondary  and  tertiary ;  Mr.  Phillips,  for  the  sake  of  uniformity,  has 
proposed  Mesozoic,  for  secondary,  from  fxetfof,  "  middle,"  <fec. ;  and  Caino- 
zoic,  for  tertiary,  from  xaivo^,  "  recent,"  <fec. ;  but  the  terms  primary,  sec- 
ondary, and  tertiary  are  synonymous,  and  have  the  claim  of  priority  in 
their  favor. 

If  we  can  prove  any  plutonic,  volcanic,  or  metamorphic  rocks  to  be 
older  than  the  secondary  formations,  such  rocks  will  also  be  primary,  ac- 
cording to  this  system.  Mr.  Boue,  having  with  propriety  excluded  the 
metamorphic  rocks,  as  a  class,  from  the  primary  formations,  proposed  to 
call  them  all  "  crystalline  schists." 

As  there  are  secondary  fossiliferous  strata,  so  we  shall  find  that  there 
are  plutonic,  volcanic,  and  metamorphic  rocks  of  contemporaneous  origin, 
which  I  shall  also  term  secondary. 

In  the  next  chapter  it  will  be  shown  that  the  strata  above  the  chalk 
have  been  called  tertiary.  If,  therefore,  we  discover  any  volcanic,  plutonic, 
or  metamorphic  rocks,  which  have  originated  since  the  deposition  of  the 
chalk,  these  also  will  rank  as  tertiary  formations. 


96  TESTS  OF  THE  DIFFERENT  AGES  [Ca.  IX. 

It  may  perhaps  be  suggested  that  some  metamorpliic  strata,  and  some 
granites,  may  be  anterior  in  date  to  the  oldest  of  the  primary  fossilifer- 
ous  rocks.  This  opinion  is  doubtless  true,  and  will  be  discussed  in  future 
chapters ;  but  I  may  here  observe,  that  when  we  arrange  the  four  classes 
of  rocks  in  four  parallel  columns  in  one  table  of  chronology,  it  is  by  no 
means  assumed  that  these  columns  are  all  of  equal  length ;  one  may 
begin  at  an  earlier  period  than  the  rest,  and  another  may  come  down  to 
a  later  point  of  time.  In  the  small  part  of  the  globe  hitherto  examined, 
it  is  hardly  to  be  expected  that  we  should  have  discovered  either  the 
oldest  or  the  newest  members  of  each  of  the  four  classes  of  rocks.  Thus, 
if  there  be  primary,  secondary,  and  tertiary  rocks  of  the  aqueous  or  fos- 
siliferous  class,  and  in  like  manner  primary,  secondary,  and  tertiary  hypo- 
gene  formations,  we  may  not  be  yet  acquainted  with  the  most  ancient  of 
the  primary  fossihferous  beds,  or  with  the  newest  of  the  hypogene. 


CHAPTER  IX. 

ON  THE  DIFFERENT  AGES  OF  THE  AQUEOUS  ROCKS. 

On  the  three  principal  tests  of  relative  age — Superposition,  mineral  character, 
and  fossils — Change  of  mineral  character  and  fossils  in  the  same  continuous 
formation — Proofs  that  distinct  species  of  animals  and  plants  have  lived  at  suc- 
cessive periods — Distinct  provinces  of  indigenous  species — Great  extent  of 
single  provinces — Similar  laws  prevailed  at  successive  geological  periods — 
Relative  importance  of  mineral  and  palaeontological  characters — Test  of  age  by 
included  fragments — Frequent  absence  of  strata  of  intervening  periods — Prin- 
cipal groups  of  strata  in  -western  Europe. 

IN  the  last  chapter  I  spoke  generally  of  the  chronological  relations  of 
the  four  great  classes  of  rocks,  and  I  shall  now  treat  of  the  aqueous  rocks 
in  particular,  or  of  the  successive  periods  at  which  the  different  fossilif- 
erous  formations  have  been  deposited. 

There  are  three  principal  tests  by  which  we  determine  the  age  of  a 
given  set  of  strata ;  first,  superposition ;  secondly,  mineral  character ; 
and,  thirdly,  organic  remains.  Some  aid  can  occasionally  be  derived 
from  a  fourth  kind  of  proof,  namely,  the  fact  of  one  deposit  including  in 
it  fragments  of  a  pre-existing  rock,  by  which  the  relative  ages  of  the  two 
may,  even  in  the  absence  of  all  other  evidence,  be  determined. 

Superposition. — The  first  and  principal  test  of  the  age  of  one  aqueous 
deposit,  as  compared  to  another,  is  relative  position.  It  has  been  already 
stated,  that  where  strata  are  horizontal,  the  bed  which  lies  uppermost  is 
the  newest  of  the  whole,  and  that  which  lies  at  the  bottom  the  most 
ancient.  So,  of  a  series  of  sedimentary  formations,  they  are  like  vol- 
umes of  history,  in  which  each  writer  has  recorded  the  annals  of  his  own 


CH.  IX.]  OF  AQUEOUS  ROCKS.  97 

times,  and  then  laid  down  the  book,  with  the  last  written  page  upper- 
most, upon  the  volume  in  which  the  events  of  the  era  immediately  pre- 
ceding were  commemorated.  In  this  manner  a  lofty  pile  of  chronicles 
is  at  length  accumulated ;  and  they  are  so  arranged  as  to  indicate,  by 
their  position  alone,  the  order  in  which  the  events  recorded  in  them  have 
occurred. 

In  regard  to  the  crust  of  the  earth,  however,  there  are  some  regions 
where,  as  the  student  has  already  been  informed,  the  beds  have  been  dis- 
turbed, and  sometimes  extensively  thrown  over  and  turned  upside  down. 
(See  pp.  58,  59.)  But  an  experienced  geologist  can  rarely  be  deceived 
by  these  exceptional  cases.  When  he  finds  that  the  strata  are  fractured, 
curved,  inclined,  or  vertical,  he  knows  that  the  original  order  of  superpo- 
sition must  be  doubtful,  and  he  then  endeavors  to  find  sections  in  some 
neighboring  district  where  the  strata  are  horizontal,  or  only  slightly  in- 
clined. Here  the  true  order  of  sequence  of  the  entire  series  of  deposits 
being  ascertained,  a  key  is  furnished  for  settling  the  chronology  of  those 
strata  where  the  displacement  is  extreme. 

Mineral  character. — The  same  rocks  may  often  be  observed  to  retain  for 
miles,  or  even  hundreds  of  miles,  the  same  mineral  peculiarities,  if  we  fol- 
low the  planes  of  stratification,  or  trace  the  beds,  if  they  be  undisturbed,  in 
a  horizontal  direction.  But  if  we  pursue  them  vertically,  or  in  any  direc- 
tion transverse  to  the  planes  of  stratification,  this  uniformity  ceases  almost 
immediately.  In  that  case  we  can  scarcely  ever  penetrate  a  stratified  mass 
for  a  few  hundred  yards  without  beholding  a  succession  of  extremely  dis- 
similar rocks,  some  of  fine,  others  of  coarse  grain,  some  of  mechanical,  others 
of  chemical  origin ;  some  calcareous,  others  argillaceous,  and  others  silice- 
ous. These  phenomena  lead  to  the  conclusion,  that  rivers  and  currents 
have  dispersed  the  same  sediment  over  wide  areas  at  one  period,  but  at 
successive  periods  have  been  charged,  in  the  same  region,  with  very  differ- 
ent kinds  of  matter.  The  first  observers  were  so  astonished  at  the  vast 
spaces  over  which  they  were  able  to  follow  the  same  homogeneous  rocks 
in  a  horizontal  direction,  that  they  came  hastily  to  the  opinion,  that  the 
whole  globe  had  been  environed  by  a  succession  of  distinct  aqueous  forma- 
tions, disposed  round  the  nucleus  of  the  planet,  like  the  concentric  coats  of 
an  onion.  But  although,  in  fact,  some  formations  may  be  continuous  over 
districts  as  large  as  half  of  Europe,  or  even  more,  yet  most  of  them  either 
terminate  wholly  within  narrower  limits,  or  soon  change  their  lithological 
character.  Sometimes  they  thin  out  gradually,  as  if  the  supply  of  sedi- 
ment had  failed  in  that  direction,  or  they  come  abruptly  to  an  end,  as  if 
we  had  arrived  at  the  borders  of  the  ancient  sea  or  lake  which  served  as 
their  receptacle.  It  no  less  frequently  happens  that  they  vary  in  mineral 
aspect  and  composition,  as  we  pursue  them  horizontally.  For  example, 
we  trace  a  limestone  for  a  hundred  miles,  until  it  becomes  more  arena- 
ceous, and  finally  passes  into  sand,  or  sandstone.  We  may  then  follow  this 
sandstone,  already  proved  by  its  continuity  to  be  of  the  same  age,  through- 
out another  district  a  hundred  miles  or  more  ia  length. 

Organic  remains. — This  character  must  be  used  as  a  criterion  of  the 


98  TESTS  OF  THE  DIFFERENT  AGES        [On.  IX 

age  of  a  formation,  or  of  the  contemporaneous  origin  of  two  deposits  in 
distant  places,  under  very  much  the  same  restrictions  as  the  test  of  min- 
eral composition. 

First,  the  same  fossils  may  be  traced  over  wide  regions,  if  we  examine 
strata  in  the  direction  of  their  planes,  although  by  no  means  for  indefi- 
nite distances. 

Secondly,  while  the  same  fossils  prevail  in  a  particular  set  of  strata 
for  hundreds  of  miles  in  a  horizontal  direction,  we  seldom  meet  with  the 
same  remains  for  many  fathoms,  and  very  rarely  for  several  hundred 
yards,  in  a  vertical  line,  or  a  line  transverse  to  the  strata.  This  fact  has 
now  been  verified  in  almost  all  parts  of  the  globe,  and  has  led  to  a  con- 
viction, that  at  successive  periods  of  the  past,  the  same  area  of  land  and 
water  has  been  inhabited  by  species  of  animals  and  plants  even  more 
distinct  than  those  which  now  people  the  antipodes,  or  which  now  co- 
exist in  the  arctic,  temperate,  and  tropical  zones.  It  appears,  that  from 
the  remotest  periods  there  has  been  ever  a  coming  in  of  new  organic 
forms,  and  an  extinction  of  those  which  pre-existed  on  the  earth ;  some 
species  having  endured  for  a  longer,  others  for  a  shorter,  time ;  while 
none  have  ever  reappeared  after  once  dying  out.  The  law  which  has 
governed  the  creation  and  extinction  of  species  seems  to  be  expressed  in 
the  verse  of  the  poet, — 

datura  il  fece,  e  poi  ruppe  la  stampa.        ARIOSTO. 
Nature  made  him,  and  then  broke  the  die. 

And  this  circumstance  it  is  which  confers  on  fossils  their  highest  value  as 
chronological  tests,  giving  to  each  of  them,  in  the  eyes  of  the  geologist, 
that  authority  which  belongs  to  contemporary  medals  in  history. 

The  same  cannot  be  said  of  each  peculiar  variety  of  rock  ;  for  some 
of  these,  as  red  marl  and  red  sandstone,  for  example,  may  occur  at  once 
at  the  top,  bottom,  and  middle  of  the  entire  sedimentary  series ;  exhib- 
iting in  each  position  so  perfect  an  identity  of  mineral  aspect  as  to  be 
undistinguishable.  Such  exact  repetitions,  however,  of  the  same  mix- 
tures of  sediment  have  not  often  been  produced,  at  distant  periods,  in 
precisely  the  same  parts  of  the  globe ;  and  even  where  this  has  hap- 
pened, we  are  seldom  in  any  danger  of  confounding  together  the  monu- 
ments of  remote  eras,  when  we  have  studied  their  imbedded  fossils  and 
their  relative  position. 

It  was  remarked  that  the  same  species  of  organic  remains  cannot  be 
traced  horizontally,  or  in  the  direction  of  the  planes  of  stratification  for 
indefinite  distances.  This  might  have  been  expected  from  analogy ;  for 
when  we  inquire  into  the  present  distribution  of  living  beings,  we  find 
that  the  habitable  surface  of  the  sea  and  land  may  be  divided  into  a 
considerable  number  of  distinct  provinces,  each  peopled  by  a  peculiar 
assemblage  of  animals  and  plants.  In  the  Principles  of  Geology,  I  have 
endeavored  to  point  out  the  extent  and  probable  origin  of  these  separate 
divisions ;  and  it  was  shown  that  climate  is  only  one  of  many  causes  on 


CH.  IX.]  OF  AQUEOUS  ROCKS.  99 

which  they  depend,  and  that  difference  of  longitude  as  well  as  latitude  is 
generally  accompanied  by  a  dissimilarity  of  indigenous  species. 

As  different  seas,  therefore,  and  lakes  are  inhabited  at  the  same  period, 
by  different  aquatic  animals  and  plants,  and  as  the  lands  adjoining  these 
may  be  peopled  by  distinct  terrestrial  species,  it  follows  that  distinct  fossils 
will  be  imbedded  in  contemporaneous  deposits.  If  it  were  otherwise — if 
the  same  species  abounded  in  every  climate,  or  in  every  part  of  the  globe 
where,  so  far  as  we  can  discover,  a  corresponding  temperature  and  other 
conditions  favorable  to  their  existence  are  found — the  identification  of 
mineral  masses  of  the  same  age,  by  means  of  their  included  organic 
contents,  would  be  a  matter  of  still  greater  certainty. 

Nevertheless,  the  extent  of  some  single  zoological  provinces,  es- 
pecially those  of  marine  animals,  is  very  great;  and  our  geological 
researches  have  proved  that  the  same  laws  prevailed  at  remote  periods ; 
for  the  fossils  are  often  identical  throughout  wide  spaces,  and  in  de- 
tached deposits,  consisting  of  rocks  varying  entirely  in  their  mineral 
nature. 

The  doctrine  here  laid  down  will  be  more  readily  understood,  if  we 
reflect  on  what  is  now  going  on  in  the  Mediterranean.  That  entire  sea 
may  be  considered  as  one  zoological  province ;  for,  although  certain 
species  of  testacea  and  zoophytes  may  be  very  local,  and  each  region  has 
probably  some  species  peculiar  to  it,  still  a  considerable  number  are  com- 
mon to  the  whole  Mediterranean.  If,  therefore,  at  some  future  period, 
the  bed  of  this  inland  sea  should  be  converted  into  land,  the  geologist 
might  be  enabled,  by  reference  to  organic  remains,  to  prove  the  contem- 
poraneous origin  of  various  mineral  masses  scattered  over  a  space  equal 
in  area  to  half  of  Europe. 

Deposits,  for  example,  are  well  known  to  be  now  in  progress  in  this 
sea  in  the  deltas  of  the  Po,  Rhone,  Nile,  and  other  rivers,  which  differ 
as  greatly  from  each  other  in  the  nature  of  their  sediment  as  does  the 
composition  of  the  mountains  which  they  drain.  There  are  also  other 
quarters  of  the  Mediterranean,  as  off  the  coast  of  Campania,  or  near  the 
base  of  Etna,  in  Sicily,  or  in  the  Grecian  Archipelago,  where  another 
class  of  rocks  is  now  forming ;  where  showers  of  volcanic  ashes  occa- 
sionally fall  into  the  sea,  and  streams  of  lava  overflow  its  bottom  ;  and 
where,  in  the  intervals  between  volcanic  eruptions,  beds  of  sand  and  clay 
are  frequently  derived  from  the  waste  of  cliffs,  or  the  turbid  waters  of 
rivers.  Limestones,  moreover,  such  as  the  Italian  travertins,  are  here 
and  there  precipitated  from  the  waters  of  mineral  springs,  some  of  which 
rise  up  from  the  bottom  of  the  sea.  In  all  these  detached  formations, 
so  diversified  in  their  lithological  characters,  the  remains  of  the  same 
shells,  corals,  Crustacea,  and  fish  are  becoming  inclosed ;  or,  at  least,  a 
sufficient  number  must  be  common  to  the  different  localities  to  enable  the 
zoologist  to  refer  them  all  to  one  contemporaneous  assemblage  of 
species. 

There  are,  however,  certain  combinations  of  geographical  circum- 
stances which  cause  distinct  provinces  of  animals  and  plants  to  be  sepa- 


100  TESTS  OF  THE  DIFFERENT  AGES  [Cn.  IX, 

rated  from  each  other  by  very  narrow  limits ;  and  hence  it  must  happen, 
that  strata  will  be  sometimes  formed  in  contiguous  regions,  differing 
widely  both  in  mineral  contents  and  organic  remains.  Thus,  for  exam- 
ple, the  testacea,  zoophytes,  and  fish  of  the  Red  Sea  are,  as  a  group,  ex- 
tremely distinct  from  those  inhabiting  the  adjoining  parts  of  the  Mediter- 
ranean, although  the  two  seas  are  separated  only  by  the  narrow  isthmus 
of  Suez.  Of  the  bivalve  shells,  according  to  Philippi,  not  more  than  -a 
fifth  are  common  to  the  Red  Sea  and  the  sea  around  Sicily,  while  the 
proportion  of  univalves  (or  Gasteropoda)  is  still  smaller,  not  exceeding 
eighteen  in  a  hundred.  Calcareous  formations  have  accumulated  on  a 
great  scale  in  the  Red  Sea  in  modern  times,  and  fossil  shells  of  existing 
species  are  well  preserved  therein  ;  and  we  know  that  at  the  mouth  of 
the  Nile  large  deposits  of  mud  are  amassed,  including  the  remains  of 
Mediterranean  species.  It  follows,  therefore,  that  if  at  some  future  pe- 
riod the  bed  of  the  Red  Sea  should  be  laid  dry,  the  geologist  might  ex- 
perience great  difficulties  in  endeavoring  to  ascertain  the  relative  age  of 
these  formations,  which,  although  dissimilar  both  in  organic  and  mineral 
characters,  were  of  synchronous  origin. 

But,  on  the  other  hand,  we  must  not  forget  that  the  northwestern 
shores  of  the  Arabian  Gulf,  the  plains  of  Egypt,  and  the  isthmus  of 
Suez,  are  all  parts  of  one  province  of  terrestrial  species.  Small  streams, 
therefore,  occasional  land-floods,  and  those  winds  which  drift  clouds  of 
sand  along  the  deserts,  might  carry  down  into  the  Red  Sea  the  same 
shells  of  fluviatile  and  land  testacea  which  the  Nile  is  sweeping  into  its 
delta,  together  with  some  remains  of  terrestrial  plants  and  the  bones  of 
quadrupeds,  whereby  the  groups  of  strata,  before  alluded  to,  might,  not- 
withstanding the  discrepancy  of  their  mineral  composition  and  marine 
organic  fossils,  be  shown  to  have  belonged  to  the  same  epoch. 

Yet  while  rivers  may  thus  carry  down  the  same  fluviatile  and  ter- 
restrial spoils  into  two  or  more  seas  inhabited  by  different  marine  species, 
it  will  much  more  frequently  happen,  that  the  coexistence  of  terrestrial 
species  of  distinct  zoological  and  botanical  provinces  will  be  proved  by 
the  identity  of  the  marine  beings  which  inhabited  the  intervening  space. 
Thus,  for  example,  the  land  quadrupeds  and  shells  of  the  south  of  Eu- 
rope, north  of  Africa,  and  northwest  of  Asia,  differ  considerably,  yet  their 
remains  are  all  washed  down  by  rivers  flowing  from  these  three  countries 
into  the  Mediterranean. 

In  some  parts  of  the  globe,  at  the  present  period,  the  line  of  demarca- 
tion between  distinct  provinces  of  animals  and  plants  is  not  very  strongly 
marked,  especially  where  the  change  is  determined  by  temperature,  as  it 
is  in  seas  extending  from  the  temperate  to  the  tropical  zone,  or  from  the 
temperate  to  the  arctic  regions.  Here  a  gradual  passage  takes  place 
from  one  set  of  species  to  another.  In  like  manner  the  geologist,  in 
studying  particular  formations  of  remote  periods,  has  sometimes  been 
able  to  trace  the  gradation  from  one  ancient  province  to  another,  by  ob- 
serving carefully  the  fossils  of  all  the  intermediate  places.  His  success 
in  thus  acquiring  a  knowledge  of  the  zoological  or  botanical  geography 


CH.  IX.] 


OF  AQUEOUS  KOCKS. 


101 


of  very  distant  eras  has  been  mainly  owing  to*tld?;'Cirdum3tancer*th*t  •  * 
the  mineral  character  has  no  tendency  to  be  affected'  by  climate. "  A 
large  river  may  convey  yellow  or  red  mud  into  some  part  of  ttel  oc4tn, : 
where  it  may  be  dispersed  by  a  current  ovej  ah  area  'severa?  hundred 
leagues  in  length,  so  as  to  pass  from  the  tropics  into  the  temperate  zone. 
If  the  bottom  of  the  sea  be  afterwards  upraised,  the  organic  remains 
imbedded  in  such  yellow  or  red  strata  may  indicate  the  different  animals 
or  plants  which  once  inhabited  at  the  same  time  the  temperate  and 
equatorial  regions. 

It  may  be  true,  as  a  general  rule,  that  groups  of  the  same  species  of 
animals  and  plants  may  extend  over  wider  areas  than  deposits  of  homo- 
geneous composition ;  and  if  so,  palaeontological  characters  will  be  of 
more  importance  in  geological  classification  than  the  test  of  mineral  com- 
position ;  but  it  is  idle  to  discuss  the  relative  ^alue  of  these  tests,  as  the 
aid  of  both  is  indispensable,  and  it  fortunately  happens,  that  where  the 
one  criterion  fails,  we  can  often  avail  ourselves  of  the  other. 

Test  by  included  fragments  of  older  rocks. — It  was  stated,  that  inde- 
pendent proof  may  sometimes  be  obtained  of  the  relative  date  of  two 
formations,  by  fragments  of  an  older  rock  being  included  in  a  newer  one. 
This  evidence  may  sometimes  be  of  great  use,  where  a  geologist  is  at  a 
loss  to  determine  the  relative  age  of  two  formations  from  want  of  clear 
sections  exhibiting  their  true  order  of  position,  or  because  the  strata  of 
each  group  are  vertical.  In  such  cases  we  sometimes  discover  that  the 
more  modern  rock  has  been  in  part  derived  from  the  degradation  of  the 
older.  Thus,  for  example,  we  may  find  chalk  with  flints  in  one  part  of  a 
country ;  and,  in  another,  a  distinct  formation,  consisting  of  alternations 
of  clay,  sand,  and  pebbles.  If  some  of  these  pebbles  consist  of  similar 
flint,  including  fossil  shells,  sponges,  and  forarniniferae,  of  the  same  species 
as  those  in  the  chalk,  we  may  confidently  infer  that  the  chalk  is  the  oldest 
of  the  two  formations. 

Chronological  groups. — The  number  of  groups  into  which  the  fossil- 
iferous  strata  may  be  separated  are  more  or  less  numerous,  according  to 
the  views  of  classification  which  different  geologists  entertain  ;  but  when* 
we  have  adopted  a  certain  system  of  arrangement,  we  immediately  find 
that  a  few  only  of  the  entire  series  of  groups  occur  one  upon  the  other 
in  any  single  section  or  district. 

The  thinning  out  of  individual  strata  was  before  described  (p.  16). 


Fig.  104. 


But  let  the  annexed  diagram  represent  seven  fossiliferous  groups,  instead 
of  as  many  strata.  It  will  then  be  seen  that  in  the  middle  all  the  super- 
imposed formations  are  present ;  but  in  consequence  of  some  of  them 


102 


CHRONOLOGICAL  ARRANGEMENT 


[CH.  IX. 


,t  v  _    0       .,  .  _c ...  No.  5  are  absent  at  one  extremity  of  the  sec- 

tic-X  and°Nt>.  4  a't  ihfe*  other. 

i  *Iojl2i«r'  *^tifi^xed  diagram,  fig.  105,  a  real  section  of  the  geological 
formtitioife"  in0^1- neighborhood  of  Bristol  and  the  Mendip  Hills,  is  pre- 
sented to  the  reader  as  laid  down  on  a  true  scale  by  Professor  Ramsay, 
where  the  newer  groups  1,  2,  3,  4  rest  unconforaiably  on  the  formations 

Fig.  105. 
Duudry  Hill. 


Section  South  of  Bristol.  A.  C.  Eamsay, 

Length  of  section  4  miles.       a,  5.  Level  of  the  sea. 

1.  Inferior  oolite.  5.  Coal  measure. 

2.  Lias.  6.  Carboniferous  limestone. 

3.  New  red  sandstone.  7.  Old  red  sandstone. 

4.  Magnesian  conglomerate. 

5  and  6.  Here  at  the  southern  end  of  the  line  of  section  we  meet  with 
the  beds  No.  3  (the  New  Red  Sandstone)  resting  immediately  on  No.  6, 
while  farther  north,  as  at  Dundry  Hill,  we  behold  six  groups  superim- 
posed one  upon  the  other,  comprising  all  the  strata  from  the  inferior 
oolite  to  the  coal  and  carboniferous  limestone.  The  limited  extension  of 
the  groups  1  and  2  is  owing  to  denudation,  as  these  formations  end  ab- 
ruptly, and  have  left  outlying  patches  to  attest  the  fact  of  their  having 
originally  covered  a  much  wider  area. 

In  many  instances,  however,  the  entire  absence  of  one  or  more  forma- 
tions of  intervening  periods  between  two  groups,  such  as  3  and  5  in  the 
same  section,  arises,  not  from  the  destruction  of  what  once  existed,  but 
because  no  strata  of  an  intermediate  age  were  ever  deposited  on  the  in- 
ferior rock.  They  were  not  formed  at  that  place,  either  because  the 
region  was  dry  land  during  the  interval,  or  because  it  was  part  of  a  sea 
or  lake  to  which  no  sediment  was  carried. 

In  order,  therefore,  to  establish  a  chronological  succession  of  fossilifer- 
ous  groups,  a  geologist  must  begin  with  a  single  section,  in  which  sev- 
eral sets  of  strata  lie  one  upon  the  other.  He  must  then  trace  these 
formations,  by  attention  to  their  mineral  character  and  fossils,  continu- 
ously, as  far  as  possible,  from  the  starting  point.  As  often  as  he  meets 
with  new  groups,  he  must  ascertain  by  superposition  their  age  relatively 
to  those  first  examined,  and  thus  learn  how  to  intercalate  them  in  a  tab- 
ular arrangement  of  the  whole. 

By  this  means  the  German,  French,  and  English  geologists  have  de- 
termined the  succession  of  strata  throughout  a  great  part  of  Europe,  and 
have  adopted  pretty  generally  the  following  groups,  almost  all  of  which 
have  their  representatives  in  the  British  Islands. 


CH.  IX.] 


OF  AQUEOUS  ROCKS. 


103 


Groups  of  Fossiliferous  Strata  observed  in  Western  Europe,  arranged 
in  what  is  termed  a  descending  Series,  or  beginning  with  the  newest. 
(See  a  more  detailed  Tabular  view,  pp.  104-108.) 


1.  Post-Pliocene,  including  those   of  the 

Recent,  or  human  period. 

2.  Newer  Pliocene,  or  Pleistocene.  1 

3.  Older  Pliocene.  I  Tertiary,  Supracretaceous,*  or 

4.  Miocene.  j       Cainozoic.f 

5.  Eocene.  J 

6.  Chalk. 

7.  Greensand  and  "Wealden. 

8.  Upper  Oolite,  including  the  Purbeck. 

9.  Middle  Oolite. 

10.  Lower  Oolite. 

11.  Lias. 

12.  Trias. 

13.  Permian. 

14.  Coal. 

15.  Old  Red  sandstone,  or  Devonian. 

16.  Upper  Silurian. 

1 7.  Lower  Silurian. 

]  S.  Cambrian  and  older  fossiliferous  strata. 


Secondary,  or  Mesozoic. 


Primary  fossiliferous,  or  palei* 
zoic. 


It  is  not  pretended  that  the  three  principal  sections  in  the  above  table, 
called  primary,  secondary,  and  tertiary,  are  of  equivalent  importance,  or 
that  the  eighteen  subordinate  groups  comprise  monuments  relating  to 
equal  portions  of  past  time,  or  of  the  earth's  history.  But  we  can  assert 
that  they  each  relate  to  successive  periods,  during  which  certain  animals 
and  plants,  for  the  most  part  peculiar  to  their  respective  eras,  have  flour- 
ished, and  during  which  different  kinds  of  sediment  were  deposited  in  the 
space  now  occupied  by  Europe. 

If  we  were  disposed,  on  palaeontological  grounds,};  to  divide  the  entire 
fossiliferous  series  into  a  few  groups  less  numerous  than  those  in  the  above 
table,  and  more  nearly  co-ordinate  in  value  than  the  sections  called  pri- 
mary, secondary,  and  tertiary,  we  might,  perhaps,  adopt  the  six  groups  or 
periods  given  in  the  next  table. 

At  the  same  time,  I  may  observe,  that,  in  the  present  state  of  the 
science,  when  we  have  not  yet  compared  the  evidence  derivable  from  all 
classes  of  fossils,  not  even  those  most  generally  distributed,  such  as 
shells,  corals,  and  fish,  such  generalizations  are  premature,  and  can  only 
be  regarded  as  conjectural  or  provisional  schemes  for  the  founding  of 
large  natural  groups. 


*  For  tertiary,  Sir  H.  De  la  Beche  has  used  the  term  "  supracretaceous," 
a  name  implying  that  the  strata  so  called  are  superior  in  position  to  the 
chalk. 

f  For  an  explanation  of  Cainozoic,  see  p.  95. 

J  Palaeontology  is  the  science  which  treats  of  fossil  remains,  both  animal  and 
vegetable.  Etym.  va\atog,  palaios,  ancient,  ovra,  onto,  beings,  and  Aoyoj,  logos,  a 
discourse. 


104 


TABULAR  VIEW   OF   FOSSILIFEROUS   STRATA.       [CH. 


Fossiliferous  Strata  of  Western  Europe  divided  into  Six  Groups. 


1.  Post-Pliocene       and 

Tertiary 

2.  Cretaceous 

3.  Oolitic     - 

4.  Triassic   - 

5.  Permian,  Carbonifer- 

ous, and  Devonian 

6.  Silurian    and    Cam- 

brian   - 


V  from  the  Post-Pliocene  to  the  Eocene  inclusive. 

-  from  the  Maestricht  Chalk  to  the  Wealden  inclusive. 

-  from  the  Purbeck  to  the  Lias  inclusive. 

_  j  including  the  Keuper,  Muschelkalk,  and  Bunter  Sand- 
stein  of  the  Germans. 

including  Magnesian  Limestone  (Zechstein),  Coal,  Moun- 
tain Limestone,  and  Old  Red  Sandstone. 

from  the  Upper  Silurian  to  the  oldest  fossiliferous  rocks 
inclusive. 


But  the  following  more  detailed  list  of  fossiliferous  strata,  divided  into 
thirty -five  sections,  will  be  required  by  the  reader  when  he  is  studying 
our  descriptions  of  the  sedimentary  formations  given  in  the  next  18 
chapters. 


TABULAE   YIEW 


OF   THE 


FOSSILIFEROUS  STRATA, 

Showing  the   Order  of  Superposition  or  Chronological  Succession  of 
the  principal  Groups. 


Periods  and  Groups. 

I.  POST-TERTIARY. 
A.  POST-PLIOCENE. 


RECENT. 


POST-PLIOCENE, 


British  Examples.  Foreign  Equivalents  and  Synonyms. 

I.  TERRAINS  CONTEMPORAINES, 

ET  QUATERNAIRES. 


Peat  of  Great  Britain  and  Ireland, 
•with  human  remains.  (Princi- 
ples of  Geology,  ch.  45.) 

Alluvial  plains  of  the  Thames, 
Mersey,  and  Rother,  with  bnried 
ships,  p.  120,  and  Principles, 
ch.  48. 


Ancient  raised  beach  of  Brighton. 
b.  fig.  331,  p.  287. 

Alluvium,  gravel,  brick-earth, 
Ac.  with  fossil  shells  of  living 
species,  but  sometimes  locally 
extinct,  and  with  bones  of  land 
animals,  partly  of  extinct  spe- 
cies ;  no  human  remains. 


Part  of  the  Terrain  quaternaire 

of  French  authors. 
Modern  part  of  deltas  of  Rhine 

Nile,  Ganges,  Mississippi,  Ac. 
Modern  part  of  coral-reef's  of  Red 

Sea  and  Pacific. 
Marine  strata  inclosing  temple  of 

Serapis  at  Puzzuoli.   Principles. 

ch.  29. 

Freshwater  strata  inclosing  Tem- 
ple in  Cashmere.  Ibid.  9th  ed. 

p.  7C2. 

Part  of  Terrain  quaternaire  of 
French  authors. 

Volcanic  tuff  of  Ischia,  with  liv 
ing  species  of  marine  shells 
and  without  human  remains  or 
•works  of  art,  p.  118. 

Loess  of  the  Rhine,  with  recent 
freshwater  shells,  and  mam- 
moth bones,  p.  121. 

Newer  part  of  boulder-formation 
in  Sweden,  p.  129.  Bluffs  of 
Mississippi,  p.  121. 


II.  TERTIARY. 
B.  PLIOCENE. 

NEWER 
PLIOCENE, 

or 
Pleistocene. 


Glacial  drift  or  boulder-formation 
of  Norfolk,  p.  132,  of  the  Clyde 
in  Scotland,  p.  130,  of  North 
Wales,  p.  136.  Norwich  Crag, 
p.  154  —Cave-deposits  of  Kirk- 
dale,  Ac.,  with  bones  of  extinct 
and  living  quadrupeds,  p.  160. 


II.   TERRAINS  TERTIAIRES. 


Terrain  quaternaire,  diluvium. 

Terrains  tertiaires  sup6rieurs,  p. 
139. 

Glacial  drift  of  Northern  Europe, 
p.  128;  and  of  Northern  United 
States,  p.  139  ;  and  Alpine  er- 
ratics, p.  148. 

Limestone  of  Girgenti,  p.  159. 

Australian  cave-breccias,  p.  161. 


Ca  IX.]       TABULAR  VIEW   OF   FOSSILIFEROUS   STRATA.  105 

Periods  and  Groups.  British  Examples  Foreign  Equivalents  and  Synonym*. 

f  Snbapennine  strata,  p.  173. 


4.  OLDER  C  Red  Crag  of  Suffolk,  pp.  168-170.  I  Hills  of  Rome,  Monte  Mario,  Ac. 

PLIOCENE.  j  Coralline  cragof  Suffolk,  pp.  168-      ^V-d^Smandy  cra«,  p. 


I  Aralo-Caspian  deposits,  p.  175. 


C.  MIOCENE. 


5.          MIOCENE. 


D.  EOCENE, 


6.  TIPPER  EOCENE 
(Lower  Miocene  of 

many  authors). 


{Marine  strata  of  this  age  wanting 
in  the  British  Isles. 
Leaf-bed  of  Mull  in  the  Hebrides  T 
p.  179. 
Lignite  of  Antrim?,  p.  180. 


IHempstead  beds,  near  Yarmouth, 
Isle  of  Wight,  p.  192. 


7.  MIDDLE  EOCENE, 


e 

8. 


1.  Bembridge,  or  Binstead  Beds, 
Isle  of  Wight,  p.  208. 

2.  Osborne  or  St.  Helen's  Series, 
p.  210. 

3.  Headon  Series.    Ibid. 

4.  Headon  Hill  Sands,  and  Bar- 
ton  Clay,  p.  212. 

5.  Bagshot     and     Bracklesham 
Beds,  p.  213. 

6.  Wanting?    Seep.  222. 


f  1.  London  Clay  and  Bognor  Beds, 

1  2.PPlast'ic  and  Mottled  Clays  and 
<      Sands,  and  Woolwich  Beds,  p. 

219. 
I  3.  Thanet  Sands,  p.  221. 


III.  SECONDARY. 
E.  CRETACEOUS. 
§  UPPER  CRETACEOUS. 

r 

9.     MAESTRICHT  j  Wanting  in  England. 

BEDS. 


10.  UPPER  j  White  Chalk  with  Flints,  of  Xorth 

WHITE  CHALK.          I      and  S0^  Downs,  p.  240. 


11.  LOWER 

WHITE  CHALK. 


13.  TIPPER 

GREENSAND. 


Chalk  without  Flints,  and  Chalk 

Marl,  p.  239. 
Chalk  Marl.    Ibid. 


f  Loose  sand   with   bright   green 

I1      grains,  p.  260. 
Firestone  of  Merstham,  Surrey,  J 
Marly  Stone  with  Chert,  Isle  of 
Wight.  I 


C.  TERRAINS  TERTIAIEES  MOT- 

EJfS,    PARIIE  SCFEK1EURE  J   OR 
FALCHS. 

Falunien  snpe'rieur,  D'Orbigny. 
Faluns  of  Touraine,  p.  175. 
Part  of  Bourdeaux  beds,  p.  178. 
Bolderberg  strata  in  Belgium,  p. 

Part  of  Vienna  basin,  p.  179. 

Part  of  Molasse,  Switzerland,  p. 
179. 

Sands  of  James  River,  and  Rich- 
mond, \  irginia,  United  States, 
.  p.  181. 

Lower  part  of  Terrain  Tertiairo 

Moyen. 
Calcaire  Lacustre  Snpgrieur  and 

Ores  de  Fontaineblean,  p.  194. 
Part  of  the  Lacustrine  strata  of 

Anvergne,  p.  194. 
Kleyu  Spawen  or  Limbnrg  beds, 

Belgium— Rupelian  and  Tong- 

rian  systems  of  Dumont,  p.  188. 
Mayence  basin,  p.  190. 
Part  of  brown-coal  of  Germany, 

pp.  191,  540. 
Hermsdorf  tile-clay  near  Berlin, 

p.  189. 
1.  Gypseous  Series  of  Montmartre, 

and  Calcaire  lacustre  superieur, 

p.  223. 

2  &  3.  Calcaire  Siliceux,  p.  225. 
2  <fc  3.  Ores  de  Beanchamp,  or 

Sables  Moyens,  p.  226.  Laecken 

beds,  Belgium. 

4  &  5.  Upper  and  Middle  Calcaire 
Grossier,  p.  226. 

5.  Bruxellien,  or  Brussels  beds  of 

Dumont. 
5.   Lower  Calcaire  Grossier,   or 

Glanconie  Grossiere,  p.  228. 

5.  Claibome     beds,     Alabama, 
United  States,  p.  232. 

5  <fc  6.  Nummnlitic  formation  oi 
Europe,  Asia.  <fec.,  p.  229. 

6.  Soissonnais  Sands,  or  Lits  Co- 
quilliers,  p.  228. 

:1.  Wanting  in  Paris  basin,  occurs 
at  Cassel,  in  French  Flanders. 
2.  Argile  Plasticine  et  Lignite,  p. 
229. 
3.  Lower  Landenian  of  Belgium 
in  part  ?,  p.  235. 

III.  TERRAINS  SECONDAIRES. 
£.  TERRAINS  CRETACEES. 


9.  Danien  of  P'OrLigny. 
Calcaire  pisolitique,  near  Paris, 

p.  235. 

Maestricht  Beds,  p.  237. 
Coralline  Limestone  of  Faxoe  in 

Denmark,  p.  238. 
10.  Senonien,  D'Orbigny. 
Craie  blanche  avec  si  lex. 
Obere  Kreide  of  the  Germans. 
Upper  Quadersandstein  r   of  the 

same. 

La  Scaglia  of  the  Italians, 
f  Calcaire  a  hippurites,  Pyrenees. 

Turonien,  D'Orbigny,  or,   Cnue 
!      tnfeau  of  Touraine. 
1  Craie  argilense  of  some  French 

[  Uppcr^Wnerkalk  of  Saxony, 
f  Gres  vert  sup6rieur. 
1  Glauconie  crayeuse. 

Craie  chlorit^e. 

Cenomanien,  D'Orbigny. 

Lower    Quadersandstein   of    the 
Germans. 


106 


TABULAR  VIEW  OF  FOSSILIFEROUS  STRATA.     [CH.  ix. 


Periods  and  Groups 
13.  GAULT. 


British  Examples. 
Dark  Blue  Marl,  Kent,  p.  250. 
Folkestone  Marl  or  Clay. 
Blackdown  Beds,  green  sand  an 
(.     chert,  Devonshire,  p.  251. 


Foreign  Equivalents  and  Synonym*, 


Ores  vert  superieur 


f  Ores 

j  Glaue 

d  1  Albie 

(.  Lowe 


come  crayeu 
bien,  D'Orbigny. 
wer  Planer  of  Saxc 


in  part. 


LOWER  CRETACEOUS,  OR  NEOCOMIAN. 


LOWER 
GREENLAND, 


15.       WEALDEX 
(Weald  Clay  and 
Hastings  Sand). 


F.  OOLITE. 

§  UPPER  OOLITE. 

16.  PURBECK  BEDS. 

17.  PORTLAND 

BEDS. 


18.     KIMMERIDGE 
CLAY. 


Sand  with  green  matter,  Weald 

of  Kent  and  Sussex,  p.  257. 
Limestone  (Kentish  Rag,)  p.  257. 
Sands  and  clay  with  calcareous 

concretions  and  chert. 
Atherfield,  Isle  of  Wight,  p.  257. 

Speeton  Clay,  Yorkshire.  (. 

Clay  with  occasional   bands    of  f 
limestone. -Weald  of  Kent,  Sur- 
rey, and  Sussex,  p.  260.  j  Formation  Waldienne 

Sand  with  calcareous  grit    and  1  NSocomien  inferieur. 


Gres  vert  infe'rieur. 
Nfiocomien  supSrieur. 
Aptien,  D'Orbigny. 
Hils-conglomerat  of  Germany. 

Hils-thon  of  Brunswick. 


clay,  —  Hastings, 
Sussex,  p.  262. 


Cuckfield,  ! 
I 


F.  TERRAINS  JURASSIQUES, 
in  part. 


C  Upper,  Middle,  and  Lower  Pnr-  C  Serpulitenkalk  of  Dunker,  and 
<  beck,  Dorsetshire  and  Wilts,  <  associated  beds  of  the  North 
(  pp.  293-296. 


§§  MIDDLE  OOLITE. 


19.     CORAL-RAG. 


30.  OXFORD  CLAY. 


Portland  stone  and  Portland  sand, 
p.  300. 


Clay    of    Kimmeridge,    Dorset- 
shire, p.  300. 


Calcareous  grit. 


(      German  Walderformation. 
Groupe  Portlandien  of  Beudant. 

Kimmeridgien,  D'Orbigny. 

Calcaire  a  gryph6es  virgules,  of 
Thirria. 

Argiles  de  Honfleur,  E.  de  Beau- 
mont et  Dufresnoy. 


Groupe  corallien  de  Beudant. 


1.  Dark  blue  clay,    Oxfordshire 
and  Midland  counties,  p.  304. 

2.  Calcareous  concretionary  lime- 
stone with  shells,  called  Kel- 
loway  Rock,  p.  34. 


§§§  LOWER  OOLITE. 


31.  GREAT  or  BATH 
OOLITE, 


INFERIOR 
OOLITE. 


G.  LIAS. 


1.  Cornbrash  and  Forest  Marble, 
Wiltshire,  p.  305. 

Oolite  and    Stonesfleld 
-Bath,   Stonesfleld,    pp. 


4  2.  Great  C 

Slate,— I 

I     305-309. 


33. 


LIAS. 


Fuller's  Earth,  near  Bath,  p.  314. 

Calcareous  freestone,  and  yellow 
sands  of  Cetteswold  Hills, 
Gloucestershire,  p.  314. 

Dundry  Hill,  near  Bristol,  pp. 
102,  314. 


1.  Upper  Lias,  p.  318. 

2.  Marl-stone,  ibid. 

3.  Lower  Lias,  ibid. 


1.  Oxfordien     snpSrieur,    Thur- 
mann. 

2.  Oxfordien  inferieur,  or  Callo- 
vien,  D'Orbigny. 


Bathonien  of  Omalius  D'Hallov. 
Grand  Oolithe. 
Calcaire  de  Caen. 


Oolithe  Inferieur. 

Oolithe  ferrugineux  of  Normandy. 

Oolithe  de  Bayeux. 

Bajocien  of  D'Orbigny. 

G.  TERRAINS  JURASSIQUES, 
in  part. 


1.  Eiage     sup6rieur     du 
Thirria. 

Toarcien  D'Orbigny. 

2.  Lias  moye 

>n 


Lias, 


3.  Calcaire  a  gryphge  arqu£e. 


Liasien,  D'Orbigny. 
gryphg 

Sin6murien,  D'Orbigny. 
Coal-field  near  Richmond,  Vir- 
ginia, p.  30. 


H.  TRIAS. 

(Upper  New  Red  Sandstone.) 


ZT.  NOUTEAU  GRES  ROUGE. 


3£.  UPPER  TRIAS. 

35.  MIDDLE  TRIAS 

or 
Muscliclkalk. 

36.  LOWER  TRIAS. 


f  Saliferous    and  Gypseous    sand-  f 

stones  and  shales  of  Cheshire,      Keuper  of  the  Germans. 
\      pp.  333-336.  \  Marnes  irisees  of  the  French. 

Bone-bed  of  Axmouth,  Devon,  p.   I  Saliferien,  D'Orbigny. 

f  f  Muschelkalk  of  the  Germans. 

\  Wanting  in  England.  \  ™$»  ™g*$»*  grcmgjart 

I  I  Conchylien,  D'Orbigny  (in  part). 

C  Red  and  white  sandstone  of  Lan-  C  Bunter-Sandstein  of  the  Germans. 
<      cashire  and  Cheshire,  pp.  336,  <  Gres  bigarr6  of  the  French. 
(     337.  (  Conchylien,  D'Orbigny  (in  part). 


CH.  IX.]       TABULAE  VIEW  OF  FOSSILIFEROUS  STRATA. 


107 


Periods  and  Group*.  British  Examples. 

IV.  PRIMARY. 

I.  PERMIAN, 
OR  MAGXESIAX  IJMESTONE. 


87. 


Foreign  Equivalents  and  Synonym*. 
IV.  TERRAINS  DK  TRANSITION. 
TERRAINS  PALEOZOIQUES. 

L  CALCAIRE  MAGNESIJBN. 


(Lower  New  lied.) 


PERMIAN, 

or 

MAGNESIAN 
LIMESTONE. 


1.  Concretionary     limestone     of 
Durham  and  Yorkshire,  p.  351. 

2.  Brecciated  limestone,  ibid. 

3.  Fossiliferous  limestone,  p.  352. 

4.  Compact  limestone,  ibid. 

5.  Marl-Slate  of  Durham,  p.  353. 

6.  Inferior  sandstones  of  various 
colors,— N.  of  England,  p.  354. 

Dolomitic    conglomerate,— Bris- 
tol, p.  354. 


1.  StinksteinofThnringia. 

2.  Rauchwacke,  ibid. 

3.  Dolomit  or  Upper  Zechstein. 

4.  Zechstein,  p.  350. 

5.  Mergel  or  Knpfer-schiefer. 

6.  Rothliegendes  of  Thuringia. 

Permian  of  Russia,  p.  355. 
Ores  des  Vosges  of  the  French 
(in  part). 


K.  CARBONIFEROUS. 


28.  UPPER 

CARBONIFEROUS 


{1.  Coal-measures, 
shale   with   sea 
West  of  Englan 
Chapters  24  and 
2.  Millstone  Grit, 


29.  LOWER 

CARBONIFEROUS. 


Coal-measures,  sandstone  and 
seams    of    coal,— 
of  England  and  Ireland, 
-»nd  25. 

pp.  358,  359. 


1.  Mountain     or     Carboniferous 
limestone,  p.  403,  tt  sea. 

2.  Lower  limestone  shale,— Men- 
dips.      Carboniferous    slate,— 
Ireland. 

Carbonaceous  schist  with  Possi- 
douomya  Becheri,  p.  409. 


K.  TERRAIN  HOUILLIER. 


Coal-fields  of  the  United  States,  p. 
387. 


1.  Calcaire    carbonifere    of   the 

French. 
1.  Bergkalk   or    Kohlenkalk    of 

the  Germans. 
1.  Pentremite  limestone,  United 

States,  p.  410. 

Eiesel-schiefer  and  Jungere 
Grauwacke  of  the  Germans,  p. 
409. 

Gypseous  beds  and  Encrinital 
limestone  of  Nova  Scotia,  p. 


L.  DEVONIAN, 
or  OLD  RED  SANDSTONE. 


30. 


31. 


UPPER 
DEVONIAN. 


LOWER 
DEVONIAN, 


Yellow  sandstone  of  Dura  Den, 

Fife.  p.  412. 
White  sandstone  of  Elgin,  with 

Telerpeton,  ibid. 
Red  sandstone  and  conglomerate, 

p.  414. 
Upper  and  middle  Devonian  of 

N.  Devon,  including  Plymouth 

limestone,  pp.  420,  *-lfe>- 

Lower  Devonian  of  N.  Devon, 
North  Foreland,  p.  424. 

Arbroath  paving-stone,  pp.  412- 
415. 

Bituminous  schists  of  Caithness, 
.  p.  418. 


TERRAIN  DEVONIEN. 

VlEUX  GRE3  ROUGE. 


Russian  Devonian,  Upper  part,  p. 

425. 
Catskill  Group,  United  States,  p. 

426. 

Eifel  Limestone,  p.  424. 
Limestone  of  Villmar,  Ac.,  Nas- 


1.  Spirifer  Sandstone  and  Slate  of 

Sandberger.  p.  424. 
Older    Rhenish    Greywacke    of 

Roemer,  ibid. 
Russian  Devonian,  Lower  part, 

p.  425. 


jr.  SILURIAN. 

33.  UPPER 

SILURIAN. 


32  a.  MIDDLE  SILURIAN. 
(Beds  of  passage  between 
Upper  and  Lower  Silurian.) 


1.  Upper  Ludlow,  p.  430. 

2.  Aymestry  Limestone,  p.  434. 

3.  Lower  Lndlow,  ibid. 

4.  Wenlock  Limestone,  p.  435. 

5.  Wenlock  shale,  p.  437. 

'  Caradoc  or  May  Hill  Sandstone,  f 


if.  TERRAIN  SILURIEN. 

New  York  division  from  the  Up- 
per  Pentamerus  to  the  Niagara 
Group  inclusive,  p.  444. 

Etages  E.  to  H.  of  Barrande, 
Bohemia. 


p.  437. 


I 


elusive,  p.  444. ' 


33. 


LOWER 
SILURIAN. 


ILlandeilo  Flags  and  shale,  p.  439.  f  New  York  groups  from  the  Hud- 

Bala  Limestone  and  black  slate,  I      son-River  beds  to  the  Calcifer- 

p.  441.  !      ous  sandstone  inclusive,  p.  444. 

Graptolite  Schists,  S.  of  Scotland.  !  Etages   and  D.  (Barrande),  Bo- 

Limestoue,  Chair  of  Kildare,  Ire-  j     hernia, 

land.  L  Slates  of  Angers,  Franee. 


N.  CAMBRIAN. 


UPPER 
CAMBRIAN. 


35.  LOWER 

CAMBRIAN. 


Lingula  Flags,  North  Wales,  p. 

448. 
Stiper  Stones,  Shropshire. 


Lowest     fossiliferous    rocks     of 
Wicklow,  in  Ireland,  p.  419. 


Primordial  zone  of  Barrande  in 

Bohemia,  p.  450. 
Alum  Schists  of  Sweden,  p.  451. 
Potsdam    Sandstone    of    United 

States  and  Canada,  p.  451. 
Wisconsin  and  Minnesota  lowest 

fossiliferous  rocks,  p.  452. 


1 08          ABEIDGED   TABLE  OF   FOSSILIFEROUS  STEATA.        [Cn.  IX. 


ABRIDGED  TABLE  OF  FOSSILIFEROUS  STRATA. 


1.  RECENT. 

2.  POST-PLIOCENE. 

3.  NEWER  PLIOCENE. 

4.  OLDER  PLIOCENE. 

5.  MIOCENE. 

6.  UPPER  EOCENE. 

7.  MIDDLE  EOCENE. 

8.  LOWER  EOCENE. 

9.  MAESTRICHT  BEDS. 

10.  UPPER  WHITE  CHALK. 

11.  LOWER  WHITE  CHALK. 

12.  UPPER  GREENSAND. 

13.  GAULT. 

14.  LOWER  GREENSAND. 

15.  WEALDEN. 

16.  PURBECK  BEDS. 

17.  PORTLAND  STONE. 

18.  KIMMERIDGE  CLAY. 

19.  CORAL  RAG. 

20.  OXFORD  CLAY. 

21.  GREAT  OB  BATH  OOLITE. 

22.  INFERIOR  OOLITE. 

23.  LIAS. 

24.  UPPER  TRIAS. 

25.  MIDDLE  TRIAS,  or 
MUSCHELKALK. 

26.  LOWER  TRIAS. 


POST-TERTIARY. 


PLIOCENE. 


MIOCENE. 


EOCENE. 


CRETACEOUS. 


JURASSIC. 


*  a 

» 

9    o 

JH 

E-I  o 

Q 

HH 

O 

N3 

i  ^ 

O 
H 
& 

§  i 

W   gj  ^q 

fr   OQ 
O        C/2 

1    i.j 

TRIASSIC. 


27.  PERMIAN,  or 
MAGNESIAN  LIMESTONE. 

28.  COAL-MEASURES. 

29.  CARBONIFEROUS 

LIMESTONE. 


30.  UPPER  j 

31.  LOWER  j 

32.  UPPER  J 

33.  LOWER  ] 

34.  UPPER  ; 

35.  LOWER ' 


DEVONIAN. 


SILURIAN. 


CAMBRIAN. 


PERMIAN. 


C  ARBONIPEROUS . 


DEVONIAN. 


SILURIAN. 


CAMBRIAN. 


Oz.  X.]  PRINCIPLES  OF  CLASSIFICATION.  109 


CHAPTER  X. 

CLASSIFICATION    OF    TERTIARY    FORMATIONS — POST-PLIOCENE    GROUP. 

General  principles  of  classification  of  tertiary  strata — Detached  formations  scat- 
tered over  Europe — Strata  of  Paris  and  London— More  modern  groups — 
Peculiar  difficulties  in  determining  the  chronology  of  tertiary  formations — In- 
creasing proportion  of  living  species  of  shells  in  strata  of  newer  -rigin — Terms 
Eocene,  Miocene,  and  Pliocene — Post-Pliocene  strata — Recent  or  human  period 
— Older  Post-Pliocene  formations  of  Naples,  Uddevalla,  and  Norway — Ancient 
upraised  delta  of  the  Mississippi — Loess  of  the  Rhine. 

BEFOR.E  describing  the  most  modern  of  the  sets  of  strata  enumerated 
in  the  tables  given  at  the  end  of  the  last  chapter,  it  will  be  necessary  to 
say  something  generally  of  the  mode  of  classifying  the  formations  called 
tertiary. 

The  name  of  tertiary  has  been  given  to  them,  because  they  are  all 
posterior  in  date  to  the  rocks  termed  "  secondary,"  of  which  the  chalk 
constitutes  the  newest  group.  These  tertiary  strata  were  at  first  con- 
founded, as  before  stated,  p.  91,  with  the  superficial  alluviums  of  Europe ; 
and  it  was  long  before  their  real  extent  and  thickness,  and  the  various 
ages  to  which  they  belong,  were  fully  recognized.  They  were  observed 
to  occur  in  patches,  some  of  freshwater,  others  of  marine  origin,  their 
geographical  area  being  usually  small  as  compared  to  the  secondary 
formations,  and  their  position  often  suggesting  tie  idea  of  their  having 
been  deposited  in  different  bays,  lakes,  estuaries,  or  inland  seas,  after  a 
large  portion  of  the  space  now  occupied  by  Europe  had  already  been 
converted  into  dry  land. 

The  first  deposits  of  this  class,  of  which  the  characters  were  accurately 
determined,  were  those  occurring  in  the  neighborhood  of  Paris,  described 
in  1810  by  MM.  Cuvier  and  Brongniart.  They  were  ascertained  to  con- 
sist of  successive  sets  of  strata,  some  of  marine,  others  of  freshwater 
origin,  lying  one  upon  the  other.  The  fossil  shells  and  corals  were  per- 
ceived to  be  almost  all  of  unknown  species,  and  to  have  in  general  a 
near  affinity  to  those  now  inhabiting  warmer  seas.  The  bones  and  skel- 
etons of  land  animals,  some  of  them  of  large  size,  and  belonging  to  more 
than  forty  distinct  species,  were  examined  by  Cuvier,  and  declared  by  him 
not  to  agree  specifically,  nor  even  for  the  most  part  generically,  with  any 
hitherto  observed  in  the  living  creation. 

Strata  were  soon  afterwards  brought  to  light  in  the  vicinity  of  London, 
and  in  Hampshire,  which  although  dissimilar  in  mineral  composition, 
were  justly  inferred  by  Mr.  T.  Webster  to  be  of  the  same  age  as  those  of 


110  PRINCIPLES  OF   CLASSIFICATION.  [Cir.  X, 

Paris,  because  the  greater  number  of  the  fossil  shells  were  specifically 
identical.  For  the  same  reason  rocks  found  on  the  Gironde,  in  the  South 
of  France,  and  at  certain  points  in  the  North  of  Italy,  were  suspected  to 
be  of  contemporaneous  origin. 

A  variety  of  deposits  were  afterwards  found  in  other  parts  of  Europe, 
all  reposing  immediately  on  rocks  as  old  or  older  than  the  chalk, 
and  which  exhibited  certain  .general  characters  of  resemblance  in  their 
organic  remains  to  those  previously  observed  near  Paris  and  London. 
An  attempt  was  therefore  made  at  first  to  refer  the  whole  to  one  pe- 
riod ;  and  when  at  length  this  seemed  impracticable,  it  was  contended 
that  as  in  the  Parisian  series  there  were  many  subordinate  formations 
of  considerable  thickness  which  must  have  accumulated  one  after  the 
other,  during  a  great  lapse  of  time,  so  the  various  patches  of  tertiary 
strata  scattered  over  Europe  might  correspond  in  age,  some  of  them 
to  the  older,  and  others  to  the  newer,  subdivisions  of  the  Parisian 
series. 

This  error,  though  almost  unavoidable  on  the '  part  of  those  who 
made  the  first  generalizations  in  this  branch  of  Geology,  retarded  se- 
riously for  some  years  the  progress  of  classification.  A  more  scrupu- 
lous attention  to  specific  distinctions,  aided  by  a  careful  regard  to  the 
relative  position  of  the  strata  containing  them,  led  at  length  to  the  con- 
viction that  there  were  formations  both  marine  and  freshwater  of  various 
ages,  and  all  newer  than  the  strata  of  the  neighborhood  of  Paris  and 
London. 

One  of  the  first  steps  in  this  chronological  reform  was  made  in  1811, 
by  an  English  naturalist,  Mr.  Parkinson,  who  pointed  out  the  fact  that 
certain  shelly  strata,  provincially  termed  "  Crag"  in  Suffolk,  lie  decidedly 
over  a  deposit  which  was  the  continuation  of  the  blue  clay  of  London. 
At  the  same  time  he  remarked  that  the  fossil  testacea  in  these  newer 
beds  were  distinct  from  those  of  the  blue  clay,  and  that  while  some  ot 
them  were  of  unknown  species,  others  were  identical  with  species  now 
inhabiting  the  British  seas. 

Another  important  discovery  was  soon  afterwards  made  by  Brocchi  in 
Italy,  who  investigated  the  argillaceous  and  sandy  deposits  replete  with 
shells  which  form  a  low  range  of  hills,  flanking  the  Apennines  on  both 
sides,  from  the  plains  of  the  Po  to  Calabria.  These  lower  hills  were 
called  by  him  the  Subapennines,  and  were  formed  of  strata  chiefly  marine, 
and  newer  than  those  of  Paris  and  London. 

Another  tertiary  group  occurring  in  the  neighborhood  of  Bourdeaux 
and  Dax,  in  the  south  of  France,  was  examined  by  M.  de  Basterot  in 
1825,  who  described  and  figured  several  hundred  species  of  shells,  which 
differed  for  the  most  part  both  from  the  Parisian  series  and  those  of  the 
Subapennine  hills.  It  was  soon,  therefore,  suspected  that  this  fauna 
might  belong  to  a  period  intermediate  between  that  of  the  Parisian  and 
Subapennine  strata,  and  it  was  not  long  before  the  evidence  of  super- 
position was  brought  to  bear  in  support  of  this  opinion  ;  for  other  strata, 
contemporaneous  with  those  of  Bourdeaux,  were  observed  in  one  district 


CH.  X.]  OF  TERTIARY  FORMATIONS.  Ill 

(the  Valley  of  the  Loire),  to  overlie  the  Parisian  formation,  and  in  an- 
other (in  Piedmont)  to  underlie  the  Subapennine  beds.  The  first  exam- 
ple of  these  was  pointed  out  in  1829  by  M.  Desnoyers,  who  ascertained 
that  the  sand  and  marl  of  marine  origin  called  Faluns,  near  Tours,  in 
the  basin  of  the  Loire,  full  of  sea-shells  and  corals,  rested  upon  a  lacus- 
trine formation,  which  constitutes  the  uppermost  subdivision  of  the 
Parisian  group,  extending  continuously  throughout  a  great  table-land 
intervening  between  the  basin  of  the  Seine  and  that  of  the  Loire.  The 
other  example  occurs  in  Italy,  "where  strata,  containing  many  fossils  sim- 
ilar to  those  of  Bourdeaux,  were  observed  by  Bonelli  and  others  in  the 
environs  of  Turin,  subjacent  to  -strata  belonging  to  the  Subapennine 
group  of  Brocchi. 

Without  pretending  to  give  a  complete  sketch  of  the  progress  of  dis- 
covery, I  may  refer  to  the  facts  above  enumerated,  as  illustrating  the 
course  usually  pursued  by  geologists  when  they  attempt  to  found  new 
chronological  divisions.  The  method  bears  some  analogy  to  that  pur- 
sued by  the  naturalist  in  the  construction  of  genera,  when  he  selects  a 
typical  species,  and  then  classes  as  congeners  all  other  species  of  animals 
and  plants  which  agree  with  this  standard  within  certain  limits.  The 
genera  A  and  C  having  been  founded  on  these  principles,  a  new  species 
is  afterwards  met  with,  departing  widely  both  from  A  and  C,  but  in 
many  respects  of  an  intermediate  character.  For  this  new  type  it  be- 
comes necessary  to  institute  the  new  genus  B,  in  which  are  included  all 
species  afterwards  brought  to  light,  which  agree  more  nearly  with  B  than 
with  the  types  of  A  or  C.  In  like  manner  a  new  formation  is  met  with 
in  geology,  and  the  characters  of  its  fossil  fauna  and  flora  investigated. 
From  that  moment  it  is  considered  as  a  record  of  a  certain  period  of  the 
earth's  history,  and  a  standard  to  which  other  deposits  may  be  com- 
pared. If  any  are  found  containing  the  same  or  nearly  the  same  organic 
remains,  and  occupying  the  same  relative  position,  they  are  regarded  in 
the  light  of  contemporary  annals.  All  such  monuments  are  said  to  re- 
late to  one  period,  during  which  certain  events  occurred,  such  as  the 
formation  of  particular  rocks  by  aqueous  or  volcanic  agency,  or  the  con- 
tinued existence  and  fossilization  of  certain  tribes  of  animals  and  plants. 
When  several  of  these  periods  have  had  their  true  places  assigned  to 
them  in  a  chronological  series,  others  are  discovered  which  it  becomes 
necessary  to  intercalate  between  those  first  known ;  and  the  difficulty  of 
assigning  clear  lines  of  separation  must  unavoidably  increase  in  propor- 
tion as  chasms  in  the  past  history  of  the  globe  are  filled  up. 

Every  zoologist  and  botanist  is  aware  that  it  is  a  comparatively  easy 
task  to  establish  genera  in  departments  which  have  been  enriched  with 
only  a  small  number  of  species,  and  where  there  is  as  yet  no  tendency 
in  one  set  of  characters  to  pass  almost  insensibly,  by  a  multitude  of  con- 
necting links,  into  another.  They  also  know  that  the  difficulty  of  classi- 
fication augments,  and  that  the  artificial  nature  of  their  divisions  becomes 
more  apparent,  in  proportion  to  the  increased  number  of  objects  brought 
to  light  But  in  separating  families  and  genera,  they  have  no  other  al- 


112  PRINCIPLES  OF  CLASSIFICATION  [Cn.  X. 

ternative  than  to  avail  themselves  of  such  breaks  as  still  remain,  or  of 
every  hiatus  in  the  chain  of  animated  beings  which  is  not  yet  filled  up. 
So  in  geology,  we  may  be  eventually  compelled  to  resort  to  sections  of 
time  as  arbitrary,  and  as  purely  conventional,  as  those  which  divide  the 
history  of  human  events  into  centuries.  But  in  the  present  state  of  our 
knowledge,  it  is  more  convenient  to  use  the  interruptions  which  still 
occur  in  the  regular  sequence  of  geological  monuments,  as  boundary 
lines  between  our  principal  groups  or  periods,  even  though  the  groups 
thus  established  are  of  very  unequal  value. 

The  isolated  position  of  distinct  tertiary  deposits  in  different  parts  of 
Europe  has  been  already  alluded  to.  In  addition  to  the  difficulty  pre- 
sented by  this  want  of  continuity  when  we  endeavor  to  settle  the  chrono- 
logical relations  of  these  deposits,  another  arises  from  the  frequent 
dissimilarity  in  mineral  character  of  strata  of  contemporaneous  date, 
such,  for  example,  as  those  of  London  and  Paris  before  mentioned.  The 
identity  or  non-identity  of  species  is  also  a  criterion  which  often  fails  us. 
For  this  we  might  have  been  prepared,  for  we  have  already  seen,  that 
the  Mediterranean  and  Red  Sea,  although  within  70  miles  of  each  other, 
on  each  side  of  the  Isthmus  of  Suez,  have  each  their  peculiar  fauna ; 
and  a  marked  difference  is  found  in  the  four  groups  of  testacea  now 
living  in  the  Baltic,  English  Channel,  Black  Sea,  and  Mediterranean,  al- 
though all  these  seas  have  many  species  in  common.  In  like  manner  a 
considerable  diversity  in  the  fossils  of  different  tertiary  formations,  which 
have  been  thrown  down  in  distinct  seas,  estuaries,  bays,  and  lakes,  does 
not  always  imply  a  distinctness  in  the  times  when  they  were  pro- 
duced, but  may  have  arisen  from  climate  and  conditions  of  physical 
geography  wholly  independent  of  time.  On  the  other  hand,  it  is  now 
abundantly  clear,  as  the  result  of  geological  investigation,  that  different 
sets  of  tertiary  strata,  immediately  superimposed  upon  each  other,  con- 
tain distinct  imbedded  species  of  fossils,  in  consequence  of  fluctuations 
which  have  been  going  on  in  the  animate  creation,  and  by  which  in  the 
course  of  ages  one  state  of  things  in  the  organic  world  has  been  substi- 
tuted for  another  wholly  dissimilar.  It  has  also  been  shown  that  in 
proportion  as  the  age  of  a  tertiary  deposit  is  more  modern,  so  is  its 
fauna  more  analogous  to  that  now  in  being  in  the  neighboring  seas.  It 
is  this  law  of  a  nearer  agreement  of  the  fossil  testacea  with  the  species 
now  living,  which  may  often  furnish  us  with  a  clue  for  the  chronological 
arrangement  of  scattered  deposits,  where  we  cannot  avail  ourselves  of 
any  one  of  the  three  ordinary  chronological  tests ;  namely,  superposition, 
mineral  character,  and  the  specific  identity  of  the  fossils. 

Thus,  for  example,  on  the  African  border  of  the  Red  Sea,  at  the 
height  of  40  feet,  and  sometimes  more,  above  its  level,  a  white  calcare- 
ous formation  has  been  observed,  containing  several  hundred  species  of 
shells  differing  from  those  found  in  the  clay  and  volcanic  tuff  of  the 
country  round  Naples,  and  of  the  contiguous  island  of  Ischia.  Another 
deposit  has  been  found  at  Uddevalla,  in  Sweden,  in  which  the  shells  do 
not  agree  with  those  found  near  Naples.  But  although  in  these  three 


Ca  X.]  OF   TERTIARY   FORMATIONS.  113 

cases  there  may  be  scarcely  a  single  shell  common  to  the  three  different 
deposits,  we  do  not  hesitate  to  refer  them  all  to  one  period  (the  Post- 
Pliocene),  because  of  the  very  close  agreement  of  the  fossil  species  in 
every  instance  with  those  now  living  in  the  contiguous  seas. 

To  take  another  example,  where  the  fossil  fauna  recedes  a  few  steps 
farther  back  from  our  own  times.  We  may  compare,  first,  the  beds  of 
loam  and  clay  bordering  the  Clyde  in  Scotland  (called  glacial  by  some 
geologists),  secondly,  others  of  fluvio-marine  origin  near  Norwich,  and, 
lastly,  a  third  set  often  rising  to  considerable  heights  in  Sicily,  and  we 
discover  that  in  every  case  more  than  three-fourths  of  the  shells  agree 
with  species  still  living,  while  the  remainder  are  extinct.  Hence  we  may 
conclude  that  all  these,  greatly  diversified  as  are  their  organic  remains, 
belong  to  one  and  the  same  era,  or  to  a  period  immediately  antecedent 
to  the  Post-Pliocene,  because  there  has  been  time  in  each  of  the  areas 
alluded  to  for  an  equal  or  nearly  equal  amount  of  change  in  the  marine 
testaceous  fauna.  Contemporaneousness  of  origin  is  inferred  in  these 
cases,  in  spite  of  the  most  marked  differences  of  mineral  character  or 
organic  contents,  from  a  similar  degree  of  divergence  in  the  shells  from 
those  now  living  in  the  adjoining  seas.  The  advantage  of  such  a  test 
consists  in  supplying  us  with  a  common  point  of  departure  in  all  coun- 
tries, however  remote. 

But  the  farther  we  recede  from  the  present  times,  and  the  smaller  the 
relative  number  of  recent  as  compared  with  extinct  species  in  the  ter- 
tiary deposits,  the  less  confidence  can  we  place  in  the  exact  value  of  such 
a  test,  especially  when  comparing  the  strata  of  very  distant  regions ;  for 
we  cannot  presume  that  the  rate  of  former  alterations  in  the  animate 
world,  or  the  continual  going  out  and  coming  in  of  species,  has  been 
everywhere  exactly  equal  in  equal  quantities  of  time.  The  form  of  the 
land  and  sea,  and  the  climate,  may  have  changed  more  in  one  region 
than  in  another  ;  and  consequently  there  may  have  been  a  more  rapid 
destruction  and  renovation  of  species  in  one  part  of  the  globe  than 
elsewhere.  Considerations  of  this  kind  should  undoubtedly  put  us  on 
our  guard  against  relying  too  implicitly  on  the  accuracy  of  this  test ; 
ye:  it  can  never  fail  to  throw  great  light  on  the  chronological  re- 
lations of  tertiary  groups  with  each  other,  and  with  the  Post-Pliocene 
period. 

We  may  derive  a  conviction  of  this  truth  not  only  from  a  study  of 
geological  monuments  of  all  ages,  but  also  by  reflecting  on  the  tendency 
which  prevails  in  the  present  state  of  nature  to  a  uniform  rate  of  simul- 
taneous fluctuation  in  the  flora  and  fauna  of  the  whole  globe.  The 
grounds  of  such  a  doctrine  cannot  be  discussed  here,  and  I  have  ex- 
plained them  at  some  length  in  the  third  Book  of  the  Principles  of 
Geology,  where  the  causes  of  the  successive  extinction  of  species  are 
considered.  It  will  be  there  seen  that  each  local  change  in  climate  and 
physical  geography  is  attended  with  the  immediate  increase  of  certain 
species,  and  the  limitation  of  the  range  of  others.  A  revolution  thus 
?ffected  is  rarely,  if  ever,  confined  to  a  limited  space,  or  to  one  geograph- 


114  FOSSIL   SHELLS.  [On.  JL 

ical  province  of  animals  or  plants,  but  affects  several  other  surrounding 
and  contiguous  provinces.  In  each  of  these,  moreover,  analogous  alter- 
ations of  the  stations  and  habitations  of  species  are  simultaneously  in 
progress,  reacting  in  the  manner  already  alluded  to  on  the  first  province. 
Hence,  long  before  the  geography  of  any  particular  district  can  be  essen- 
tially altered,  the  flora  and  fauna  throughout  the  world  will  have  been 
materially  modified  by  countless  disturbances  in  the  mutual  relation  of 
the  various  members  of  the  organic  creation  to  each  other.  To  assume 
that  in  one  large  area  inhabited  exclusively  by  a  single  assemblage  of 
species  any  important  revolution  in  physical  geography  can  be  brought 
about,  while  other  areas  remain  stationary  in  regard  to  the  position  of 
land  and  sea,  the  height  of  mountains,  and  so  forth,  is  a  most  improba- 
ble hypothesis,  wholly  opposed  to  what  we  know  of  the  laws  now 
governing  the  aqueous  and  igneous  causes.  On  the  other  hand,  even 
were  this  conceivable,  the  communication  of  heat  and  cold  between  dif- 
ferent parts  of  the  atmosphere  and  ocean  is  so  free  and  rapid,  that  the 
temperature  of  certain  zones  cannot  be  materially  raised  or  lowered 
without  others  being  immediately  affected ;  and  the  elevation  or  dimi- 
nution in  height  of  an  important  chain  of  mountains  or  the  submergence 
of  a  wide  tract  of  land  would  modify  the  climate  even  of  the  antipodes. 

It  will  be  observed  that  in  the  foregoing  allusions  to  organic  remains, 
the  testacea  or  the  shell-bearing  mollusca  are  selected  as  the  most  useful 
and  convenient  class  for  the  purposes  of  general  classification.  In  the 
first  place,  they  are  more  universally  distributed  through  strata  of  every 
age  than  any  other  organic  bodies.  Those  families  of  fossils  which  are 
of  rare  and  casual  occurrence  are  absolutely  of  no  avail  in  establishing 
a  chronological  arrangement.  If  we  have  plants  alone  in  one  group  of 
strata  and  the  bones  of  mammalia  in  another,  we  can  draw  no  conclusion 
respecting  the  affinity  or  discordance  of'  the  organic  beings  of  the  two 
epochs  compared ;  and  the  same  may  be  said  if  we  have  plants  and 
vertebrated  animals  in  one  series  and  only  shells  in  another.  Although 
corals  are  more  abundant,  in  a  fossil  state,  than  plants,  reptiles,  or  fish, 
they  are  still  rare  when  contrasted  with  shells,  especially  in  the  European 
tertiary  formations.  The  utility  of  the  testacea  is,  moreover,  enhanced 
by  the  circumstance  that  some  forms  are  proper  to  the  sea,  others  to  the 
land,  and  others  to  freshwater.  Rivers  scarcely  ever  fail  to  carry  down 
into  their  deltas  some  land  shells,  together  with  species  which  are  at 
once  fluviatile  and  lacustrine.  By  this  means  we  learn  what  terrestrial, 
freshwater,  and  marine  species  coexisted  at  particular  eras  of  the  past ; 
and  having  thus  identified  strata  formed  in  seas  with  others  which  origi- 
nated contemporaneously  in  inland  lakes,  we  are  then  enabled  to  advance 
a  step  farther,  and  show  that  certain  quadrupeds  or  aquatic  plants,  found 
fossil  in  lacustrine  formations,  inhabited  the  globe  at  the  same  period 
when  certain  fish,  reptiles,  and  zoophytes  lived  in  the  ocean. 

Among  other  characters  of  the  molluscous  animals,  which  render 
them  extremely  valuable  in  settling  chronological  questions  in  geology, 
may  be  mentioned,  first,  the  wide  geographical  range  of  many  species  * 


CH.  X.]  FOSSIL   SHELLS.  115 

and,  secondly,  what  is  probably  a  consequence  of  the  former,  the  great 
duration  of  species  in  this  class,  for  they  appear  to  have  surpassed  in 
longevity  the  greater  number  of  the  mammalia  and  fish.  Had  each 
species  inhabited  a  very  limited  space,  it  could  never,  when  imbedded  in 
strata,  have  enabled  the  geologist  to  identify  deposits  at  distant  points  ; 
or  had  they  each  lasted  but  for  a  brief  period,  they  could  have  thrown 
no  light  on  the  connection  of  rocks  placed  far  from  each  other  in  the 
chronological,  or,  as  it  is  often  termed,  vertical  series. 

Many  authors  have  divided  the  European  tertiary  strata  into  three 
groups — lower,  middle,  and  upper;  the  lower  comprising  the  oldest 
formations  of  Paris  and  London  before-mentioned  ;  the  middle  those  of 
Bourdeaux  and  Touraine  ;  and  the  upper  all  those  newer  than  the  mid- 
dle group. 

When  engaged  in  1828  in  preparing  my  work  on  the  Principles  of 
Geology,  I  conceived  the  idea  of  classing  the  whole  series  of  tertiary 
strata  in  four  groups,  and  endeavoring  to  find  characters  for  each,  ex- 
pressive of  their  different  degrees  of  affinity  to  the  living  fauna.  With 
this  view,  I  obtained  information  respecting  the  specific  identity  of  many 
tertiary  and  recent  shells  from  several  Italian  naturalists,  and  among 
others  from  Professors  Bonelli,  Guidotti,  and  Costa.  Having  in  1829 
become  acquainted  with  M.  Deshayes,  of  Paris,  already  well  known  by 
his  conchological  works,  I  learnt  from  him  that  he  had  arrived,  by  inde- 
pendent researches,  and  by  the  study  of  a  large  collection  of  fossil  and 
recent  shells,  at  very  similar  views  respecting  the  arrangement  of  tertiary 
formations.  At  my  request  he  drew  up,  in  a  tabular  form,  lists  of  all 
the  shells  known  to  him  to  occur  both  in  some  tertiary  formation  and  in 
a  living  state,  for  the  express  purpose  of  ascertaining  the  proportional 
number  of  fossil  species  identical  with  the  recent  which  characterized 
successive  groups ;  and  this  table,  planned  by  us  in  common,  was  pub- 
lished by  me  in  1833.*  The  number  of  tertiary  fossil  shells  examined 
by  M.  Deshayes  was  about  3000 ;  and  the  recent  species  with  which  they 
had  been  compared  about  5000.  The  result  then  arrived  at  was,  that 
in  the  lower  tertiary  strata,  or  those  of  London  and  Paris,  there  were 
about  3i  per  cent  of  species  identical  with  recent ;  in  the  middle  ter- 
tiary of  the  Loire  and  Gironde  about  17  per  cent.;  and  in  the  upper 
tertiary  or  Subapennine  beds,  from  35  to  50  per  cent.  In  formations 
still  more  modern,  some  of  which  I  had  particularly  studied  in  Sicily, 
where  they  attain  a  vast  thickness  and  elevation  above  the  sea,  the  num- 
ber of  species  identical  with  those  now  living  was  believed  to  be  from 
90  to  95  per  cent.  For  the  sake  of  clearness  and  brevity,  I  proposed 
to  give  short  technical  names  to  these  four  groups,  or  the  periods  to 
which  they  respectively  belonged.  I  called  the  first  or  oldest  of  them 
Eocene,  the  second  Miocene,  the  third  Older  Pliocene,  and  the  last  or 
fourth  Xewer  Pliocene.  The  first  of  the  above  terms,  Eocene,  is  derived 
from  iju£,  eos,  dawn,  and  xaivos,  cainos,  recent,  because  the  fossil  shells  of 

*  See  Pr-inc.  of  Geol.  vol.  iii.  1st  ed. 


116      FOURFOLD   DIVISION   OF  TERTIARY   FORMATIONS.       [On.  X, 

this  period  contain  an  extremely  small  proportion  of  living  species,  which 
may  be  looked  upon  as  indicating  the  dawn  of  the  existing  state  of  tha 
testaceous  fauna,  no  recent  species  having  been  detected  in  the  older  or 
secondary  rocks. 

The  term  Miocene  (from  |ut.£iov,  meion,  less,  and  xajvoj,  cainos,  recent) 
is  intended  to  express  a  minor  proportion  of  recent  species  (of  testacea), 
the  term  Pliocene  (from  wXsfov,  pleion,  more,  and  xaivo£,  cainos,  recent)  a 
comparative  plurality  of  the  same.  It  may  assist  the  memory  of  stu- 
dents to  remind  them,  that  the  J/wcene  contain  a  wmor  proportion,  and 
Pliocene  a  comparative  ^/urality  of  recent  species ;  and  that  the  greater 
number  of  recent  species  always  implies  the  more  modern  origin  of  the 
strata. 

It  has  sometimes  been  objected  to  this  nomenclature  that  certain  spe- 
cies of  infusoria  found  in  the  chalk  are  still  existing,  and,  on  the  other 
hand,  the  Miocene  and  Older  Pliocene  deposits  often  contain  the  remains 
of  mammalia,  reptiles,  and  fish,  exclusively  of  extinct  species.  But  the 
reader  must  bear  in  mind  that  the  terms  Eocene,  Miocene,  and  Pliocene 
were  originally  invented  with  reference  purely  to  conchological  data,  and 
in  that  sense  have  always  been  and  are  still  used  by  me. 

The  distribution  of  the  fossil  species  from  which  the  results  before  men- 
tioned were  obtained  in  1830  by  M.  Deshayes  was  as  follows  : — 

In  the  formations  of  the  Pliocene  periods,  older  and  newer  -      777 
In  the  Miocene  -     1021 

In  the  Eocene  -     123S 

3036 


Since  the  year  1830,  the  number  of  new  living  species  obtained 
from  different  parts  of  the  globe  has  been  exceedingly  great,  supplying 
fresh  data  for  comparison,  and  enabling  the  paleontologist  to  correct 
many  erroneous  identifications  of  fossil  and  recent  forms.  New  spe- 
cies also  have  been  collected  in  abundance  from  tertiary  formations  of 
every  age,  while  newly  discovered  groups  of  strata  have  filled  up  gaps 
in  the  previously  known  series.  Hence  modifications  and  reforms  have 
been  called  for  in  the  classification  first  proposed.  The  Eocene,  Miocene, 
and  Pliftcene  periods  have  been  made  to  comprehend  certain  sets  of 
strata  of  which  the  fossils  do  not  always  conform  strictly  in  the  propor- 
tion of  recent  to  extinct  species  with  the  definitions  first  given  by  me,  or 
which  are  implied  in  the  etymology  of  those  terms.  Of  these  and  other 
innovations  I  shall  treat  more  fully  in  the  14th  and  15th  chapters. 

POST-PLIOCENE  FORMATIONS. 

I  have  adopted  the  term  Post-Pliocene  for  those  strata  which  are 
sometimes  called  post-tertiary  or  modern,  and  which  are  characterized 


Ca  X.]  POST-PLIOCEXE  FORMATIONS.  117 

by  having  all  the  imbedded  fossil  shells  identical  with  species  now  living, 
whereas  even  the  Newer  Pliocene,  or  newest  of  the  tertiary  deposits 
above  alluded  to,  contain  always  some  small  proportion  of  shells  of  ex- 
tinct species. 

These  modern  formations,  thus  defined,  comprehend  not  only  those 
strata  which  can  be  shown  to  have  originated  since  the  earth  was  inhab- 
ited by  man,  but  also  deposits  of  far  greater  extent  and  thickness,  in 
which  no  signs  of  man  or  his  works  can  be  detected.  In  some  of  these, 
of  a  date  long  anterior  to  the  times  of  history  and  tradition,  the  bones 
of  extinct  quadrupeds  have  been  met  with  of  species  which  probably 
never  co-existed  with  the  human  race,  as,  for  example,  the  mammoth, 
mastodon,  megatherium,  and  others,  and  yet  the  shells  are  the  same  as 
those  now  living. 

That  portion  of  the  post-pliocene  group  which  belongs  to  the  human 
epoch,  and  which  is  sometimes  called  Recent,  forms  a  very  unimportant 
feature  in  the  geological  structure  of  the  earth's  crust.  I  have  shown, 
however,  in  "  The  Principles,"  where  the  recent  changes  of  the  earth 
illustrative  of  geology  are  described  at  length,  that  the  deposits  accumu- 
lated at  the  bottom  of  lakes  and  seas  within  the  last  4000  or  5000  years 
can  neither  be  insignificant  in  volume  or  extent.  They  lie  hidden,  for 
the  most  part,  from  our  sight ;  but  we  have  opportunities  of  examining 
them  at  certain  points  where  newly  gained  land  in  the  deltas  of  rivers 
has  been  cut  through  during  floods,  or  where  coral  reefs  are  growing 
rapidly,  or  where  the  bed  of  a  sea  or  lake  has  been  heaved  up  by  sub- 
terranean movements  and  laid  dry.  Their  age  may  be  recognized  either 
by  our  finding  in  them  the  bones  of  man  in  a  fossil  state,  that  is  to  say, 
imbedded  in  them  by  natural  causes,  or  by  their  containing  articles  fab- 
ricated by  the  hands  of  man. 

Thus  at  Puzzuoli,  near  Naples,  marine  strata  are  seen  containing  frag- 
ments of  sculpture,  pottery,  and  the  remains  of  buildings,  together  with 
innumerable  shells  retaining  in  part  their  color,  and  of  the  same  species 
as  those  now  inhabiting  the  Bay  of  Baiae.  The  uppermost  of  these 
beds  is  about  20  feet  above  the  level  of  the  sea.  Their  emergence  can 
be  proved  to  have  taken  place  since  the  beginning  of  the  sixteenth  cen- 
tury.* Now  here,  as  in  almost  every  instance  where  any  alterations  of 
level  have  been  going  on  in  historical  periods,  it  is  found  that  rocks  contain- 
ing shells,  all,  or  nearly  all,  of  which  still  inhabit  the  neighboring  sea,  may 
be  traced  for  some  distance  into  the  interior,  and  often  to  a  considerable 
elevation  above  the  level  of  the  sea.  Thus,  in  the  country  round  Na- 
ples, the  post-pliocene  strata,  consisting  of  clay  and  horizontal  beds  of 
volcanic  tuff,  rise  at  certain  points  to  the  height  of  1500  feet.  Although 
the  marine  shells  are  exclusively  of  living  species,  they  are  not  accom- 
panied like  those  on  the  coast  at  Puzzuoli  by  any  traces  of  man  or  his 
works.  Had  any  such  been  discovered,  it  would  have  afforded  to  the 
antiquary  and  geologist  matter  of  great  surprise,  since  it  would  have 

*  See  Principles,  Index,  "  Serapis." 


118  POST-PLIOCENE  FORMATIONS.  [On.  X. 

shown  that  man  was  an  inhabitant  of  that  part  of  the  globe,  while  the 
materials  composing  the  present  hills  and  plains  of  Campania  were  still 
in  the  progress  of  deposition  at  the  bottom  of  the  sea ;  whereas  wre 
know  that  for  nearly  3000  years,  or  from  the  times  of  the  earliest  Greek 
colonists,  no  material  revolution  in  the  physical  geography  of  that  part 
of  Italy  has  occurred. 

In  Ischia,  a  small  island  near  Naples,  composed  in  like  manner  or 
marine  and  volcanic  formations,  Dr.  Philippi  collected  in  the  stratified 
tuff  and  clay  ninety-two  species  of  shells  of  existing  species.  In  the 
centre  of  Ischia,  the  lofty  hill  called  Epomeo,  or  San  Nicola,  is  composed 
of  greenish  indurated  tuff,  of  a  prodigious  thickness,  interstratified  in 
some  parts  with  marl,  and  here  and  there  with  great  beds  of  solid  lava. 
Visconti  ascertained  by  trigonometrical  measurement  that  this  mountain 
was  2605  feet  above  the  level  of  the  sea.  Not  far  from  its  summit,  at 
the  height  of  about  2000  feet,  as  also  near  Moropano,  a  village  only  100 
feet  lower,  on  the  southern  declivity  of  the  mountain,  I  collected,  in 
1828,  many  shells  of  species  now  inhabiting  the  neighboring  gulf.  It 
is  clear,  therefore,  that  the  great  mass  of  Epomeo  was  not  only  raised  to 
its  present  height,  but  was  also  formed  beneath  the  waters,  within  the 
post-pliocene  period. 

It  is  a  fact,  however,  of  no  small  interest,  that  the  fossil  shells  from 
these  modern  tuffs  of  the  volcanic  regions  surrounding  the  Bay  of  Baise, 
although  none  of  them  extinct,  indicate  a  slight  want  of  correspondence 
between  the  ancient  fauna  and  that  now  inhabiting  the  Mediterranean. 
Philippi  informs  us  that  when  he  and  M.  Scacchi  had  collected  ninety- 
nine  species  of  them,  he  found  that  only  one,  Pecten  medius,  now  living 
in  the  Red  Sea,  was  absent  from  the  Mediterranean.  Notwithstanding 
this,  he  adds,  "  the  condition  of  the  sea  when  the  tufaceous  beds  were 
deposited  must  have  been  considerably  different  from  its  present  state  ; 
for  Tellina  striata  was  then  common,  and  is  now  rare  ;  Lucina  spinosa 
was  both  more  abundant  and  grew  to  a  larger  size ;  Lucina  fragilis, 
now  rare,  and  hardly  measuring  6  lines,  then  attained  the  enormous 
dimensions  of  14  lines,  and  was  extremely  abundant ;  and  Ostrea  la- 
mellosa,  Broc.,  no  longer  met  with  near  Naples,  existed  at  that  time, 
and  attained  a  size  so  large  that  one  lower  valve  has  been  known  to 
measure  5  inches  9  lines  in  length,  4  inches  in  breadth,  1^  inch  in  thick 
ness,  "and  weighed  26^  ounces."* 

There  are  other  parts  of  Europe  where  no  volcanic  action  manifests 
itself  at  the  surface,  as  at  Naples,  whether  by  the  eruption  of  lava  or  by 
earthquakes,  and  yet  where  the  land  and  bed  of  the  adjoining  sea  are 
undergoing  upheaval.  The  motion  is  so  gradual  as  to  be  insensible  tc 
the  inhabitants,  being  only  ascertainable  by  careful  scientific  measure- 
ments compared  after  long  intervals.  Such  an  upward  movement  has 
been  proved  to  be  in  progress  in  Norway  and  Sweden  throughout  an 
area  about  1000  miles  N.  and  S.,  and  for  an  unknown  distance  E  and 

*  Geol.  Quart.  Journ.  vol.  il  Memoirs,  p.  15. 


CH.  X.]  RECENT   STRATA   IN   SWEDEN.  119 

W.,  the  amount  of  elevation  always  increasing  as  we  proceed  toward? 
the  North  Cape,  where  it  may  equal  5  feet  in  a  century.  If  we  could 
assume  that  there  had  been  an  average  rise  of  2^  feet  in  each  hundred 
years  for  the  last  fifty  centuries,  this  would  give  an  elevation  of  125  feet 
in  that  period.  In  other  words,  it  would  follow  that  the  shores,  and  a 
considerable  area  of  the  former  bed  of  the  Baltic  and  North  Sea,  had 
been  uplifted  vertically  to  that  amount,  and  converted  into  land  in  the 
course  of  the  last  5000  years.  Accordingly,  we  find  near  Stockholm,  in 
Sweden,  horizontal  beds  of  sand,  loam,  and  marl  containing  the  same 
peculiar  assemblage  of  testacea  which  now  live  in  the  brackish  waters 
of  the  Baltic.  Mingled  with  these,  at  different  depths,  have  been  de- 
tected various  works  of  art  implying  a  rude  state  of  civilization,  and 
some  vessels  built  before  the  introduction  of  iron,  the  whole  marine 
formation  having  been  upraised,  so  that  the  upper  beds  are  now  60  feet 
higher  than  the  surface  of  the  Baltic.  In  the  neighborhood  of  these 
recent  strata,  both  to  the  northwest  and  south  of  Stockholm,  other 
deposits  similar  in  mineral  composition  occur,  which  ascend  to  greater 
heights,  in  which  precisely  the  same  assemblage  of  fossil  shells  is  met 
with,  but  without  any  intermixture  of  human  bones  or  fabricated  articles. 

On  the  opposite  or  western  coast  of  Sweden,  at  Uddevalla,  post-plio- 
cene strata,  containing  recent  shells,  not  of  that  brackish  water  character 
peculiar  to  the  Baltic,  but  such  as  now  live  in  the  northern  ocean,  ascend 
to  the  height  of  200  feet ;  and  beds  of  clay  and  sand  of  the  same  age 
attain  elevations  of  300  and  even  700  feet  in  Norway,  where  they  have 
been  usually  described  as  "  raised  beaches."  They  are,  however,  thick 
deposits  of  submarine  origin,  spreading  far  and  wide,  and  filling  valleys 
in  the  granite  and  gneiss,  just  as  the  tertiary  formations,  in  different 
parts  of  Europe,  cover  or  fill  depressions  in  the  older  rocks. 

It  is  worthy  of  remark,  that  although  the  fossil  fauna  characterizing 
these  upraised  sands  and  clays  consists  exclusively  of  existing  northern 
species  of  testacea,  yet,  according  to  Loven  (an  able  living  naturalist  of 
Norway),  the  species  do  not  constitute  such  an  assemblage  as  now  in- 
habits corresponding  latitudes  in  the  German  Ocean.  On  the  contrary, 
they  decidedly  represent  a  more  arctic  fauna.*  In  order  to  find  the 
same  species  flourishing  in  equal  abundance,  or  in  many  cases  to  find 
them  at  all,  we  must  go  northwards  to  higher  latitudes  than  Uddevalla 
in  Sweden,  or  even  nearer  the  pole  than  Central  Norway. 

Judging  by  the  uniformity  of  climate  now  prevailing  from  century  to 
century,  and  the  insensible  rate  of  variation  in  the  organic  world  in  our 
own  times,  we  may  presume  that  an  extremely  lengthened  period  was 
required  even  for  so  slight  a  modification  of  the  molluscous  fauna,  as 
that  of  which  the  evidence  is  here  brought  to  light.  On  the  other  hand, 
we  have  every  reason  for  inferring  on  independent  grounds  (namely,  the 
rate  of  upheaval  of  land  in  modern  times)  that  the  antiquity  of  the 
deposits  in  question  must  be  very  great.  For  if  we  assume,  as  before 

*  Quart.  GeoL  Journ.  4  Mems.  p.  48 


120  KECENT  AND   POST-PLIOCENE  FORMATIONS.          [Cii.  X 

suggested,  that  the  mean  rate  of  continuous  vertical  elevation  has 
amounted  to  2J  feet  in  a  century  (and  this  is  probably  a  high  average), 
it  would  require  27,500  years  for  the  sea-coast  to  attain  the  height  of 
700  feet,  without  making  allowance  for  any  pauses  such  as  are  now  ex- 
perienced in  a  large  part  of  Norway,  or  for  any  oscillations  of  level. 

In  England,  buried  ships  have  been  found  in  the  ancient  and  now 
deserted  channels  of  the  Rother  in  Sussex,  of  the  Mersey  in  Kent,  and 
the  Thames  near  London.  Canoes  and  stone  hatchets  have  been  dug 
up,  in  almost  all  parts  of  the  kingdom,  from  peat  and  shell-marl ;  but 
there  is  no  evidence,  as  in  Sweden,  Italy,  and  many  other  parts  of  the 
world,  of  the  bed  of  the  sea,  and  the  adjoining  coast,  having  been  up- 
lifted bodily  to  considerable  heights  within  the  human  period.  Recent 
strata  have  been  traced  along  the  coasts  of  Peru  and  Chili,  inclosing 
shells  in  abundance,  all  agreeing  specifically  with  those  now  swarming  in 
the  Pacific.  In  one  bed  of  this  kind,  in  the  island  of  San  Lorenzo,  near 
Lima,  Mr.  Darwin  found,  at  the  altitude  of  85  feet  above  the  sea,  pieces 
of  cotton-thread,  plaited  rush,  and  the  head  of  a  stalk  of  Indian  corn, 
the  whole  of  which  had  evidently  been  imbedded  with  the  shells.  At 
the  same  height  on  the  neighboring  mainland,  he  found  other  signs  cor- 
roborating the  opinion  that  the  ancient  bed  of  the  sea  had  there  also 
been  uplifted  85  feet,  since  the  region  was  first  peopled  by  the  Peruvian 
race.*  But  similar  shelly  masses  are  also  met  with  at  much  higher 
elevations,  at  innumerable  points  between  the  Chilian  and  Peruvian 
Andes  and  the  sea-coast,  in  which  no  human  remains  were  ever,  or  in 
all  probability  ever  will  be,  discovered. 

In  the  West  Indies,  also,  in  the  island  of  Guadaloupe,  a  solid  lime- 
stone occurs,  at  the  level  of  the  sea-beach,  enveloping  human  skeletons. 
The  stone  is  extremely  hard,  and  chiefly  composed  of  comminuted  shell 
and  coral,  with  here  and  there  some  entire  corals  ,and  shells,  of  species 
now  living  in  the  adjacent  ocean.  With  them  are  included  arrow-heads, 
fragments  of  pottery,  and  other  articles  of  human  workmanship.  A 
limestone  with  similar  contents  has  been  formed,  and  is  still  forming,  in 
St.  Domingo.  But  there  are  also  more  ancient  rocks  in  the  West  Indian 
Archipelago,  as  in  Cuba,  near  the  Havana,  and  in  other  islands,  in 
which  af :  shells  identical  with  those  now  living  in  corresponding  lati- 
tudes ;  some  well-preserved,  others  in  the  state  of  casts,  all  referable  to 
the  post-pliocene  period. 

I  have  already  described  in  the  seventh  chapter,  p.  84,  what  would  be 
the  effects  of  oscillations  and  changes  of  level  in  any  region  drained  by 
a  great  river  and  its  tributaries,  supposing  the  area  to  be  first  depressed 
several  hundred  feet,  and  then  re-elevated.  I  believe  that  such  changes 
in  the  relative  level  of  land  and  sea  have  actually  occurred  in  the  post- 
pliocene  era  in  the  hydrographical  basin  of  the  Mississippi  and  in  that 
of  the  Rhine.  The  accumulation  of  fluviatile  matter  in  a  delta  during 
a  slow  subsidence  may  raise  the  newly  gained  land  superficially  at  the 

*  Journal,  p.  451. 


CH.  X.]  PLAIN  OF   THE   MISSISSIPPI.  121 

same  rate  at  which  its  foundations  sink,  so  that  these  may  go  down  hun- 
dreds or  thousands  of  feet  perpendicularly,  and  yet  the  sea  bordering  the 
delta  may  always  be  excluded,  the  whole  deposit  continuing  to  be  terres- 
trial or  freshwater  in  character.  This  appears  to  have  happened  in  the 
deltas  both  of  the  Po  and  Ganges,  for  recent  artesian  borings,  penetrating 
to  the  depth  of  400  feet,  have  there  shown  that  fluviatile  strata,  with 
shells  of  recent  species,  together  with  ancient  surfaces  of  land  supporting 
turf  and  forests,  are  depressed  hundreds  of  feet  below  the  sea  level.* 
Should  these  countries  be  once  more  slowly  upraised,  the  rivers  would 
carve  out  valleys  through  the  horizontal  and  unconsolidated  strata  as  they 
rose,  sweeping  away  the  greater  portion  of  them,  and  leaving  mere  frag- 
ments in  the  shape  of  terraces  skirting  newly-formed  alluvial  plains,  as 
monuments  of  the  former  levels  at  which  the  rivers  ran.  Of  this  nature 
are  "  the  bluffs,"  or  river  cliffs,  now  bounding  the  valley  of  the  Mississippi 
throughout  a  large  portion  of  its  "  course."  The  upper  portions  of  these 
bluffs  which  at  Natchez  and  elsewhere  often  rise  to  the  height  of  200  feet 
above  the  alluvial  plain,  consist  of  loam  containing  land  and  freshwater 
shells  of  the  genera  Helix,  Pupa,  Succinea,  and  Lymnea,  of  the  same 
species  as  those  now  inhabiting  the  neighboring  forests  and  swamps.  In 
the  same  loam  also  are  found  the  bones  of  the  Mastodon,  Elephant,  Mega- 
lonyx,  and  other  extinct  quadrupeds.f 

I  have  endeavored  to  show  that  the  deposits  forming  the  delta  and 
alluvial  plain  of  the  Mississippi  consist  of  sedimentary  matter,  extend- 
ing over  an  area  of  30,000  square  miles,  and  known  in  some  parts  to  be 
several  hundred  feet  deep.  Although  we  cannot  estimate  correctly  how 
many  years  it  may  have  required  for  the  river  to  bring  down  from  the 
upper  country  so  large  a  quantity  of  earthy  matter — the  data  for  such  a 
computation  being  as  yet  incomplete — we  may  still  approximate  to  a 
minimum  of  the  time  which  such  an  operation  must  have  taken,  by  as- 
certaining experimentally  the  annual  discharge  of  water  by  the  Mississippi, 
and  the  mean  annual  amount  of  solid  matter  contained  in  its  waters.  The 
lowest  estimate  of  the  time  required  would  lead  us  to  assign  a  high  an- 
tiquity, amounting  to  many  tens  of  thousands  of  years  to  the  existing 
delta,  the  origin  of  which  is  nevertheless  an  event  of  yesterday  when  con- 
trasted with  the  terraces  formed  of  the  loam  above  mentioned.  The  ma- 
terials of  the  bluffs  were  produced  during  the  first  part  of  a  great  oscilla- 
tion of  level  which  depressed  to  a  depth  of  200  feet  a  larger  area  than  the 
modern  delta  and  plain  of  the  Mississippi,  and  then  restored  the  whole 
region  to  its  former  position.^ 

Loess  of  the  Valley  of  the  Rhine. — A  similar  succession  of  geograph- 
ical changes  attended  by  the  production  of  a  fluviatile  formation,  singu- 
larly resembling  that  which  bounds  the  great  plain  of  the  Mississippi, 
seems  to  have  occurred  in  the  hydrographical  basin  of  the  Rhine,  since 

*  See  Principles,  8th  ed.  pp.  260-268,  9th  ed.  257-280. 

f  See  Principles  of  GeoL  9th  ed.,  and  Lyell's  Second  Visit  to  the  United  States, 
vol.  ii.  p.  257. 

£  Lyell's  Second  Visit  to  the  United  States,  vol.  ii.  chap.  34. 


122  LOESS   OF   THE   VALLEY   OF   THE   KHINE.  [Cn.  X. 

the  time  when  that  basin  had  already  acquired  its  present  outline  of  hill 
and  valley.  I  allude  to  the  deposit  provincially  termed  loess  in  part  of 
Germany,  or  lehm  in  Alsace,  filled  with  land  and  freshwater  shells  of 
existing  species.  It  is  a  finely  comminuted  sand  or  pulverulent  loam  of  a 
yellowish  gray  color,  consisting  chiefly  of  argillaceous  matter  combined 
with  a  sixth  part  of  carbonate  of.  lime,  and  a  sixth  of  quartzose  and 
micaceous  sand.  It  often  contains  calcareous  sandy  concretions  or  nod- 
ules, rarely  exceeding  the  size  of  a  man's  head.  Its  entire  thickness 
amounts,  in  some  places,  to  between  200  and  300  feet;  yet  there  are 
often  no  signs  of  stratification  in  the  mass,  except  here  and  there  at  the 
bottom,  where  there  is  occasionally  a  slight  intermixture  of  drifted  ma- 
terials derived  from  subjacent  rocks.  Unsolidified  as  it  is,  and  of  so 
perishable  a  nature,  that  every  streamlet  flowing  over  it  cuts  out  for 
itself  a  deep  gully,  it  usually  terminates  in  a  vertical  cliff,  from  the  sur- 
face of  which  land-shells  are  seen  here  and  there  to  project  in  relief.  In 
all  these  features  it  presents  a  precise  counterpart  to  the  loess  of  the 
Mississippi.  It  is  so  homogeneous  as  generally  to  exhibit  no  signs  of 
stratification,  owing,  probably,  to  its  materials  having  been  derived  from 
a  common  source,  and  having  been  accumulated  by  a  uniform  action. 
Yet  it  displays  in  some  few  places  decided  marks  of  successive  deposi- 
tion, where  coarser  and  finer  materials  alternate,  especially  near  the  bot- 
tom. Calcareous  concretions,  also  inclosing  land-shells,  are  sometimes 
arranged  in  horizontal  layers.  It  is  a  remarkable  deposit,  from  its  posi- 
tion, wide  extent,  and  thickness,  its  homogeneous  mineral  composition, 
and  freshwater  origin.  Its  distribution  clearly  shows  that  after  the  great 
valley  of  the  Rhine,  from  Schaffhausen  to  Bonn,  had  acquired  its  present 
form,  having  its  bottom  strewed  over  with  coarse  gravel,  a  period  arrived 
when  it  became  filled  up  from  side  to  side  with  fine  mud,  probably  de- 
posited during  river  inundations  ;  and  it  is  also  clear  that  similar  mud 
and  silt  were  thrown  down  contemporaneously  in  the  valleys  of  the  prin- 
cipal tributaries  of  the  Rhine. 

Thus,  for  example,  it  may  be  traced  far  into  Wiirtemberg,  up  the  val- 
ley of  the  Neckar,  and  from  Frankfort,  up  the  valley  of  the  Main,  to 
above  Dettelbach.  I  have  also  seen  it  spreading  over  the  country  of 
Mayence,  Eppelsheim,  and  Worms,  on  the  left  bank  of  the  Rhine,  and 
on  the  opposite  side  on  the  table-land  above  the  Bergstrasse,  between 
Wiesloch  and  Bruchsal,  where  it  attains  a  thickness  of  200  feet.  Near 
Strasburg,  large  masses  of  it  appear  at  the  foot  of  the  Vosges  on  the  left 
bank,  and  at  the  base  of  the  mountains  of  the  Black  Forest  on  the  right 
bank.  The  Kaiserstuhl,  a  volcanic  mountain  which  stands  in  the  middle 
of  the  plane  of  the  Rhine  near  Freiburg,  has  been  covered  almost  every- 
where with  this  loam,  as  have  the  extinct  volcanoes  between  Coblentz 
and  Bonn.  Near  Andernach,  in  the  Kirchweg,  the  loess  containing  the 
usual  shells  alternates  with  volcanic  matter  ;  and  over  the  whole  are 
strewed  layers  of  pumice,  lapilli,  and  volcanic  sand,  from  10  to  15  feet 
thick,  very  much  resembling  the  ejections  under  which  Pompeii  lies 
buried.  There  is  no  passage  at  this  upper  junction  from  the  loess  into 


CH.  X.]  LOESS   OF  THE   RHINE.  123 

the  pumiceous  superstratum ;  and  this  last  follows  the  slope  of  the  hill, 
just  as  it  would  have  done  had  it  fallen  in  showers  from  the  air  on  a 
declivity  partly  formed  of  loess. 

But,  in  general,  the  loess  overlies  all  the  volcanic  products,  even  those 
between  Neuwied  and  Bonn,  which  have  the  most  modern  aspect ;  and 
it  has  filled  up  in  part  the  crater  of  the  Roderberg,  an  extinct  volcano 
near  Bonn.  In  1833  a  well  was  sunk  at  the  bottom  of  this  crater, 
through  70  feet  of  loess,  in  part  of  which  were  the  usual  calcareous  con- 
cretions. 

The  interstratification  above  alluded  to,  of  loess  with  layers  of  pumice 
and  volcanic  ashes,  has  led  to  the  opinion  that  both  during  and  since  its 
deposition  some  of  the  last  volcanic  eruptions  of  the  Lower  Eifel  have 
taken  place.  Should  such  a  conclusion  be  adopted,  we  should  be  called 
upon  to  assign  a  very  modern  date  to  these  eruptions.  This  curious 
point,  therefore,  deserves  to  be  reconsidered ;  since  it  may  possibly  have 
happened  that  the  waters  of  the  Rhine,  swollen  by  the  melting  of  snow 
and  ice,  and  flowing  at  a  great  height  through  a  valley  choked  up  with 
loess,  may  have  swept  away  the  loose  superficial  scoriae  and  pumice  of 
the  Eifel  volcanoes,  and  spread  them  out  occasionally  over  the  yellow 
loam.  Sometimes,  also,  the  melting  of  snow  on  the  slope  of  small  vol- 
canic cones  may  have  given  rise  to  local  floods,  capable  of  sweeping  down 
light  pumice  into  the  adjacent  low  grounds. 

The  first  idea  which  has  occurred  to  most  geologists,  after  examining 
the  loess  between  Mayence  and  Basle,  is  to  imagine  that  a  great  lake 
once  extended  throughout  the  valley  of  the  Rhine  between  those  two 
places.  Such  a  lake  may  have  sent  oft'  large  branches  up  the  course  of 
the  Main,  ISTeckar,  and  other  tributary  valleys,  in  all  of  which  large 
patches  of  loess  are  now  seen.  The  barrier  of  the  lake  might  be  placed 
somewhere  in  the  narrow  and  picturesque  gorge  of  the  Rhine  between 
Bingen  and  Bonn.  But  this  theory  fails  altogether  to  explain  the  phe- 
nomena ;  when  we  discover  that  that  gorge  itself  has  once  been  filled 
with  loess,  which  must  have  been  tranquilly  deposited  in  it,  as  also  in 
the  lateral  valley  of  the  Lahn,  communicating  with  the  gorge.  The 
loess  has  also  overspread  the  high  adjoining  platform  near  the  village  of 
Plaidt  above  Andernach.  Nay,  on  proceeding  farther  down  to  the  north, 
we  discover  that  the  hills  which  skirt  the  great  valley  between  Bonn  and 
Cologne  have  loess  on  their  flanks,  which  also  covers  here  and  there  the 
gravel  of  the  plain  as  far  as  Cologne,  and  the  nearest  rising  grounds. 

Besides  these  objections  to  the  lake  theory,  the  loess  is  met  with  near 
Basle,  capping  hills  more  than  1200  feet  above  the  sea  ;  so  that  a  barrier 
of  land  capable  of  separating  the  supposed  lake  from  the  ocean  would  re- 
quire to  be,  at  least,  as  high  as  the  mountains  called  the  Siebengebirge, 
near  Bonn,  the  loftiest  summit  of  which,  the  Oehlberg,  is  1209  feet  above 
the  Rhine,  and  1369  above  the  sea.  It  would  be  necessary,  moreover,  to 
place  this  lofty  barrier  somewhere  below  Cologne,  or  precisely  where  the 
level  of  the  land  is  now  lowest. 

Instead,  therefore,  of  supposing  one  continuous  lake  of  sufficient  extent 


124  LOESS   OF   THE   RHINE  [Cn.  X. 

and  depth  to  allow  of  the  simultaneous  accumulation  of  the  loess,  at  various 
heights,  throughout  the  whole  area  where  it  now  occurs,  I  formerly  suggest- 
ed that,  subsequently  to  the  period  when  the  countries  now  drained  by  the 
Rhine  and  its  tributaries  had  nearly  acquired  their  actual  form  and  geo- 
graphical features,  they  were  again  depressed  gradually  by  a  movement 
like  that  now  in  progress  on  the  west  coast  of  Greenland.*  In  propor- 
tion as  the  whole  district  was  lowered,  the  general  fall  of  the  waters 
between  the  Alps  and  the  ocean  was  lessened  ;  and  both  the  main  and 
lateral  valleys,  becoming  more  subject  to  river  inundations,  were  partially 
filled  up  with  fluviatile  silt,  containing  land  and  freshwater  shells.  When 
a  thickness  of  many  hundred  feet  of  loess  had  been  thrown  down  slowly 
by  this  operation,  the  whole  region  was  once  more  upheaved  gradually. 
During  this  upward  movement  most  of  the  fine  loam  would  be  carried 
off  by  the  denuding  power  of  rains  and  rivers ;  and  thus  the  original 
valleys  might  have  been  re-excavated,  and  the  country  almost  restored  to 
its  pristine  state,  with  the  exception  of  some  masses  and  patches  of  loess 
such  as  still  remain,  and  which,  by  their  frequency  s*nd  remarkable  ho- 
mogeneousness  of  composition  and  fossils,  attest  the  ancient  continuity 
and  common  origin  of  the  whole.  By  imagining  these  oscillations  of 
level,  we  dispense  with  the  necessity  of  erecting  and  afterwards  removing 
a  mountain  barrier  sufficiently  high  to  exclude  the  ocean  from  the  valley 
of  the  Rhine  during  the  period  of  the  accumulation  of  the  loess. 

The  proportion  of  land  shells  of  the  genera  Helix,  Pupa,  and  Buli- 
mus,  is  very  large  in  the  loess ;  but  in  many  places  aquatic  species  of 
the  genera  Lymnea,  Paludina,  and  Planorbis  are  also  found.  Thesf; 
may  have  been  carried  away  during  floods  from  shallow  pools  and 
marshes  bordering  the  river ;  and  the  great  extent  of  marshy  ground 
caused  by  the  wide  overflowings  of  rivers  above  supposed  would  favor 
the  multiplication  of  amphibious  mollusks,  such  as  the  Succinea  (fig. 
106),  which  is  almost  everywhere  characteristic  of  this  formation,  and  is 
sometimes  accompanied,  as  near  Bonn,  by  another  species,  S.  amphibia 
(fig.  34,  p.  29).  Among  other  abundant  fossils  are  Helix  plebeia  and 
Pupa  mvscorum.  (See  Figures.)  Both  the  terrestrial  and  aquatic  she-lls 
preserved  in  the  loess  are  of  most  fragile  and  delicate  structure,  and  yet, 

Fig.  106.  Fig.  107.  Fig.  108. 


Succinea  elongata.          Pupa  muscorum.  Helix  plebeia. 

they  are  almost  invariably  perfect  and  uninjured.  They  must  have  been 
broken  to  pieces  had  they  been  swept  along  by  a  violent  inundation. 
Even  the  color  of  some  of  the  land-shells,  as  that  of  Helix  nevioralis,  is 
occasionally  preserved. 

*  Princ.  of  Geol.  3d  edition,  1834,  vol.  iii.  p.  414. 


Ca  X.]  AND   ITS  FOSSILS.  125 

Bones  of  vertebrated  animals  are  rare  in  the  loess,  but  those  of  the 
mammoth,  horse,  and  some  other  quadrupeds  have  been  met  with.  At 
the  village  of  Binningen,  and  the  hills  called  Bruder  Holz,  near  Basle,  I 
found  the  vertebrae  of  fish,  together  with  the  usual  shells.  These  ver- 
tebrae, according  to  M.  Agassiz,  belong  decidedly  to  the  Shark  family, 
perhaps  to  the  genus  Lamna.  In  explanation  of  their  occurrence  among 
land  and  freshwater  shells,  it  may  be  stated  that  certain  fish  of  this  fam- 
ily ascend  the  Senegal,  Amazon,  and  other  great  rivers,  to  the  distance 
of  several  hundred  miles  from  the  ocean.* 

At  Cannstadt,  near  Stuttgardt,  in  a  valley  also  belonging  to  the  hydro- 
graphical  basin  of  the  Rhine,  I  have  seen  the  loess  pass  downwards  into 
beds  of  calcareous  tuff  and  travertin.  Several  valleys  in  northern  Ger- 
many, as  that  of  the  Hm  at  Weimar,  and  that  of  the  Tonna,  north  of 
Gotha,  exhibit  similar  masses  of  modern  limestone  filled  with  recent 
shells  of  the  genera  Planorbis,  Lymnea,  P>aludina,  &c.,  from  50  to  80 
feet  thick,  with  a  bed  of  loess  much  resembling  that  of  the  Rhine,  occa- 
sionally incumbent  on  them.  In  these  modern  limestones  used  for  build- 
ing, the  bones  of  Elephas  primigenius.  Rhinoceros  tichorinus,  Ursus, 
spelceus,  Hycena  spelcea,  with  the  horse,  ox,  deer,  and  other  quadrupeds, 
occur;  and  in  1850  Mr.  H.  Credner  and  I  obtained  in  a  quarry  at  Ton- 
na, at  the  depth  of  15  feet,  inclosed  in  the  calcareous  rock  and  surrounded 
with  dicotyledonous  leaves  and  petrified  leaves,  four  eggs  of  a  snake  of 
the  size  of  the  largest  European  Coluber,  which,  with  three  others,  were 
lying  in  a  series,  or  string. 

They  are,  I  believe,  the  first  reptilian  remains  which  have  been  met 
with  in  strata  of  this  age. 

The  agreement  of  the  shells  in  these  cases  with  recent  European  species 
enables  us  to  refer  to  a  very  modern  period  the  filling  up  and  re-excava- 
tion of  the  valleys ;  an  operation  which  doubtless  consumed  a  long  period 
of  time,  since  which  the  mammiferous  fauna  has  undergone  a  considerable 

*  Proceedings  of  Geol.  Soc.  No.  43,  p.  222. 


126  BOULDER  FORMATION.  [On.  XL 

CHAPTER  XL 

NEWER    PLIOCENE    PERIOD BOULDER    FORMATION. 

Drift  of  Scandinavia,  northern  Germany,  and  Russia — Its  northern  origin — Not 
all  of  the  same  age — Fundamental  rocks  polished,  grooved,  and  scratched — 
Action  of  glaciers  and  icebergs — Fossil  shells  of  glacial  period — Drift  of  eastern 
Norfolk — Associated  freshwater  deposit — Bent  and  folded  strata  lying  on  un- 
disturbed beds— Shells  on  Moel  Tryfane — Ancient  glaciers  of  North  Wales — 
Irish  drift. 

AMONG  the  different  kinds  of  alluvium  described  in  the  seventh  chapter, 
mention  was  made  of  the  boulder  formation  in  the  north  of  Europe,  the 
peculiar  characters  of  which  may  now  be  considered,  as  it  belongs  in 
part  to  the  post-pliocene,  and  partly  to  the  newer  pliocene,  period.  I 
shall  first  allude  briefly  to  that  portion  of  it  which  extends  from  Finland 
and  the  Scandinavian  mountains  to  the  north  of  Russia,  and  the  low 
countries  bordering  the  Baltic,  and  which  has  been  traced  southwards  as 
far  as  the  eastern  coast  of  England.  This  formation  consists  of  mud, 
sand,  and  clay,  sometimes  stratified,  but  often  wholly  devoid  of  stratifica- 
tion, for  a  depth  of  more  than  a  hundred  feet.  To  this  unstratified  form 
of  the  deposit,  the  name  of  till  has  been  applied  in  Scotland.  It  gen- 
erally contains  numerous  fragments  of  rocks,  some  angular  and  others 
rounded,  which  have  been  derived  from  formations  of  all  ages,  both  fos- 
siliferous,  volcanic,  and  hypogene,  and  which  have  often  been  brought 
from  great  distances.  Some  of  the  travelled  blocks  are  of  enormous 
size,  several  feet  or  yards  in  diameter ;  their  average  dimensions  increas- 
ing as  we  advance  northwards.  The  till  is  almost  everywhere  devoid  of 
organic  remains,  unless  where  these  have  been  washed  into  it  from  older 
formations ;  so  that  it  is  chiefly  from  relative  position  that  we  must  hope 
to  derive  a  knowledge  of  its  age. 

Although  a  large  proportion  of  the  Boulder  deposit,  or  "  northern  drift," 
as  it  has  sometimes  been  called,  is  made  up  of  fragments  brought  from  a 
distance,  and  which  have  sometimes  travelled  many  hundred  miles,  the 
bulk  of  the  mass  in  each  locality  consists  of  the  ruins  of  subjacent  or 
neighboring  rocks  ;  so  that  it  is  red  in  a  region  of  red  sandstone,  white  in 
a  chalk  countiy,  and  gray  or  black  in  a  district  of  coal  and  coal-shale. 

The  fundamental  rock  on  which  the  boulder  formation  reposes,  if  it 
consists  of  granite,  gneiss,  marble,  or  other  hard  stone  capable  of  perma- 
nently retaining  any  superficial  markings  which  may  have  been  imprinted 
upon  it,  is  usually  smoothed  or  polished,  and  exhibits  parallel  striae  and 
furrows  having  a  determinate  direction.  This  direction,  both  in  Europe 
and  North  America,  is  evidently  connected  with  the  course  taken  by  the 
erratic  blocks  in  the  same  district  being  from  north  to  south,  or  if  it  be 
20  or  30  degrees  to  the  east  or  west  of  north,  always  corresponding  to  the 
direction  in  which  the  large  angular  and  rounded  stones  have  travelled. 


CH.  XI.]  KOCKS   DEIFTED   BY  ICE.  127 

These  stones  themselves  also  are  often  furrowed  and  scratched  on  more 
than  one  side. 

In  explanation  of  such  phenomena  I  may  refer  the  student  to  what  was 
said  of  the  action  of  glaciers  and  icebergs  in  the  Principles  of  Geology 
(ch.  xv.).  It  is  ascertained  that  hard  stones,  frozen  into  a  moving  mass  of 
ice,  and  pushed  along  under  the  pressure  of  that  mass,  scoop  out  long 
rectilinear  furrows  or  grooves  parallel  to  each  other  on  the  subjacent 
solid  rock.  (See  fig.  109.)  Smaller  scratches  and  strise  are  made  on 

Fi«.  109. 


Limestone  polished,  farrowed,  and  scratched  by  the  glacier  of  Kosenlaui,  in  Switzerland.  (Agassiz.) 

a  a.  "White  streaks  or  scratches,  caused  by  small  grains  of  flint  frozen  into  the  ice. 
&  &.  Furrows. 

the  polished  surface  by  crystals  or  projecting  edges  of  the  hardest  min- 
erals, just  as  a  diamond  cuts  glass.  The  recent  polishing  and  striation 
of  limestone  by  coast-ice  carrying  boulders  even  as  far  south  as  the  coast 
01  Denmark,  has  been  observed  by  Dr.  Forchhammer,  and  helps  us  to 
conceive  how  large  icebergs,  running  aground  on  the  bed  of  the  sea,  may 
produce  similar  furrows  on  a  grander  scale.  An  account  was  given  so 
long  ago  as  the  year  1822,  by  Scoresby,  of  icebergs  seen  by  him  drifting 
along  in  latitudes  69°  and  70°  N.,  which  rose  above  the  surface  from 
100  to  200  feet,  and  measured  from  a  few  yards  to  a  mile  in  circumfer- 
ence. Many  of  them  were  loaded  with  beds  of  earth  and  rock,  of  such 
thickness  that  the  weight  was  conjectured  to  be  from  50,000  to  100,000 
tons.*  A  similar  transportation  of  rocks  is  known  to  be  in  progress  in 
the  southern  hemisphere,  where  boulders  included  in  ice  are  far  more 
frequent  than  in  the  north.  One  of  these  icebergs  was  encountered  in 
1839,  in  mid-ocean,  in  the  antarctic  regions,  many  hundred  miles  from 
any  known  land,  sailing  northwards,  with  a  large  erratic  block  firmly 

*  Voyages  in  1822,  p.  233. 


128  ORIGIN   OF  TILL.  [CH.  XI. 

frozen  into  it.  In  order  to  understand  in  what  manner  long  and  straight 
grooves  may  be  cut  by  such  agency,  we  must  remember  that  these  float- 
ing islands  of  ice  have  a  singular  steadiness  of  motion,  in  consequence 
of  the  larger  portion  of  their  bulk  being  sunk  deep  under  water,  so  that 
they  are  not  perceptibly  moved  by  the  winds  arid  waves  even  in  the 
strongest  gales.  Many  had  supposed  that  the  magnitude  commonly 
attributed  to  icebergs  by  unscientific  navigators  was  exaggerated,  but 
now  it  appears  that  the  popular  estimate  of  their  dimensions  has  rather 
fallen  within  than  beyond  the  truth.  Many  of  them,  carefully  measured 
by  the  officers  of  the  French  exploring  expedition  of  the  Astrolabe,  were 
between  100  and  225  feet  high  above  water,  and  from  2  to  5  miles  in 
length.  Captain  d'Urville  ascertained  one  of  them  which  he  saw  float- 
ing in  the  Southern  Ocean  to  be  13  miles  long  and  100  feet  high,  with 
walls  perfectly  vertical.  The  submerged  portions  of  such  islands  must, 
according  to  the  weight  of  ice  relatively  to  sea-water,  be  from  six  to  eight 
times  more  considerable  than  the  part  which  is  visible,  so  that  the  mechan- 
ical power  they  might  exert  when  fairly  set  in  motion  must  be  prodigious.'* 
A  large  proportion  of  these  floating  masses  of  ice  is  supposed  not  to  be  de- 
rived from  terrestrial  glaciers,  f  but  to  be  formed  at  the  foot  of  cliffs  by 
the  drifting  of  snow  from  the  land  over  the  frozen  surface  of  the  sea. 

We  know  that  in  Switzerland,  when  glaciers  laden  with  mud  and  stones 
melt  away  at  their  lower  extremity  before  reaching  the  sea,  they  leave 
wherever  they  terminate  a  confused  heap  of  unstratified  rubbish,  called 
"  a  moraine,"  composed  of  mud,  sand,  and  pieces  of  all  the  rocks  with 
which  they  were  loaded.  We  may  expect,  therefore,  to  find  a  formation 
of  the  same  kind,  resulting  from  the  liquefaction  of  icebergs,  in  tranquil 
water.  But,  should  the  action  of  a  current  intervene  at  certain  points  or 
at  certain  seasons,  then  the  materials  will  be  sorted  as  they  fall,  and  ar- 
ranged in  layers  according  to  their  relative  weight  and  size.  Hence  there 
will  be  passages  from  till,  as  it  is  called  in  Scotland,  to  stratified  clay, 
gravel,  and  sand,  and  intercalations  of  one  in  the  other. 

I  have  yet  to  mention  another  appearance  connected  with  the  boulder 
formation,  which  has  justly  attracted  much  attention  in  Norway  and  other 
parts  of  Europe.  Abrupt  pinnacles  and  outstanding  ridges  of  rock  are 
often  observed  to  be  polished  and  furrowed  on  the  north  side,  or  on  the 
side  facing  the  region  from  which  the  erratics  have  come  ;  while,  on  the 
other,  which  is  usually  steeper  and  often  perpendicular,  called  the  "  lee- 
side,"  such  superficial  markings  are  wanting.  There  is  usually  a  collec- 
tion on  this  lee-side  of  boulders  and  gravel,  or  of  large  angular  fragments. 
In  explanation  we  may  suppose  that  the  north  side  was  exposed,  when 
still  submerged,  to  the  action  of  icebergs,  and  afterwards,  when  the  land 
was  upheaved,  of  coast-ice  which  ran  aground  upon  shoals,  or  was  packed 
on  the  beach ;  so  that  there  would  be  great  wear  and  tear  on  the  sea- 
ward slope,  while,  on  the  other,  gravel  and  boulders  might  be  heaped  up 
in  a  sheltered  position. 

Northern  origin  of  erratics, — That  the  erratics  of  northern  Europe 
*  T.  L.  Hayes,  Boston  Journ.  Nat.  Hist.  1844.  f  Principles,  ch.  xv. 


CH.  XL]  STRATA   CONTAINING   RECENT   SHELLS.  129 

have  been  carried  southward  cannot  be  doubted ;  those  of  granite,  for 
example,  scattered  over  large  districts  of  Russia  and  Poland,  agree  pre- 
cisely in  character  with  rocks  of  the  mountains  of  Lapland  and  Finland ; 
while  the  masses  of  gneiss,  syenite,  porphyry,  and  trap,  strewed  over  the 
low  sandy  countries  of  Pomerania,  Holstein,  and  Denmark  are  identical 
in  mineral  characters  with  the  mountains  of  Norway  and  Sweden. 

It  is  found  to  be  a  general  rule  in  Russia,  that  the  smaller  blocks  are 
carried  to  greater  distances  from  their  point  of  departure  than  the  larger ; 
the  distance  being  sometimes  800  and  even  1000  miles  from  the  nearest 
rocks  from  which  they  were  broken  off;  the  direction  having  been  from 
N.  W.  to  S.  K,  or  from  the  Scandinavian  mountains  over  the  seas  and 
low  lands  to  the  southeast.  That  its  accumulation  throughout  this  area 
took  place  in  part  during  the  post-pliocene  period  is  proved  by  its  super- 
position at  several  points  to  strata  containing  recent  shells.  Thus,  for 
example,  in  European  Russia,  MM.  Murchison  and  De  Verneuil  found  in 
1840,  that  the  flat  country  between  St.  Petersburg  and  Archangel,  for  a 
distance  of  600  miles,  consisted  of  horizontal  strata,  full  of  shells  similar 
to  those  now  inhabiting  the  arctic  sea,  on  which  rested  the  boulder  forma- 
tion, containing  large  erratics. 

In  Sweden,  in  the  immediate  neighborhood  of  Upsala,  I  had  observed,  in 
1834,  a  ridge  of  stratified  sand  and  gravel,  in  the  midst  of  which  occurs  a 
layer  of  marl,  evidently  formed  originally  at  the  bottom  of  the  Baltic,  by 
the  slow  growth  of  the  mussel,  cockle,  and  other  marine  shells  of  living  spe- 
cies, intermixed  with  some  proper  to  freshwater.  The  marine  shells  arc  all  of 
dwarfish  size,  like  those  now  inhabiting  the  brackish  waters  of  the  Baltic ; 
and  the  marl,  in  which  myriads  of  them  are  imbedded,  is  now  raised 
more  than  100  feet  above  the  level  of  the  Gulf  of  Bothnia.  Upon  the 
top  of  this  ridge  repose  several  huge  erratics,  consisting  of  gneiss  for  the 
most  part  unrounded,  from  9  to  16  feet  in  diameter,  and  which  must 
have  been  brought  into  their  present  position  since  the  time  when  the 
neighboring  gulf  was  already  characterized  by  its  peculiar  fauna.*  Here, 
therefore,  we. have  proof  that  the  transport  of  erratics  continued  to  take 
place,  not  merely  when  the  sea  was  inhabited  by  the  existing  testacea, 
but  when  the  north  of  Europe  had  already  assumed  that  remarkable 
feature  of  its  physical  geography,  which  separates  the  Baltic  from  the 
North  Sea,  and  causes  the  Gulf  of  Bothnia  to  have  only  one-fourth  of 
the  saltness  belonging  to  the  ocean.  In  Denmark,  also,  recent  shells 
have  been  found  in  stratified  beds,  closely  associated  with  the  boulder 
clay. 

It  was  stated  that  in  Russia  the  erratics  diminished  generally  in  size 
in  proportion  as  they  are  traced  farther  from  their  source.  The  same 
observation  holds  true  in  regard  to  the  average  bulk  of  the  Scandinavian 
boulders,  when  we  pursue  them  southwards,  from  the  south  of  Norway 
and  Sweden  through  Denmark  and  Westphalia.  This  phenomenon  is 
in  perfect  harmony  with  the  theory  of  ice-islands  floating  in  a  sea  of 

*  See  paper  by  the  author,  Phil.  Trans.  1835.  p.  15. 


130 


FOSSILS   OF    ARCTIC   SPECIES. 


XI 


-ariable  depth ;  for  the  heavier  erratics  require  icebergs  of  a  larger  size 
to  buoy  them  up ;  and  even  when  there  are  no  stones  frozen  in,  more 
than  seven-eighths,  and  often  nine-tenths,  of  a  mass  of  drift-ice  is  under 
water.  The  greater,  therefore,  the  volume  of  the  iceberg,  the  sooner 
would  it  impinge  on  some  shallower  part  of  the  sea ;  while  the  smaller 
and  lighter  floes,  laden  with  finer  mud  and  gravel,  may  pass  freely  over 
the  same  banks,  and  be  carried  to  much  greater  distances.  In  those 
places,  also,  where  in  the  course  of  centuries  blocks  have  been  carried 
southwards  by  coast-ice,  having  been  often  stranded  and  again  set  afloat 
in  the  direction  of  a  prevailing  current,  the  blocks  will  diminish  in  size 
the  farther  they  travel  from  their  point  of  departure  for  two  reasons :  first, 
because  they  will  be  repeatedly  exposed  to  wear  and  tear  by  the  action  of 
the  waves ;  secondly,  because  the  largest  blocks  are  seldom  without  di- 
visional planes  or  "joints,"  which  cause  them  to  split  when  weathered. 
Hence  as  often  as  they  start  on  a  fresh  voyage,  becoming  buoyant  by 
coast-ice  which  has  frozen  on  to  them,  one  portion  of  the  mass  is  detached 
from  the  rest.  A  recent  examination  (in  1852)  of  several  trains  of  huge 
erratics  in  lat.  42°  50'  IS",  in  the  United  States,  in  Berkshire,  on  the  west- 
ern confines  of  Massachusetts,  has  convinced  me  that  this  cause  has  been 
very  influential  both  in  reducing  the  size  of  erratics,  and  in  restoring  an- 
gularity to  blocks  which  would  otherwise  be  rounded  in  proportion  to 
their  distance  from  their  original  starting  point. 

The  "  northern  drift"  of  the  most  southern  latitudes  is  usually  of  the 
highest  antiquity.  In  Scotland  it  rests  immediately  on  the  older  rocks, 
and  is  covered  by  stratified  sand  and  clay,  usually  devoid  of  fossils,  but 
in  which,  at  certain  points  near  the  east  and  west  coast,  as,  for  example, 
in  the  estuaries  of  the  Tay  and  Clyde,  marine  shells  have  been  discovered. 
The  same  shells  have  also  been  met  with  in  the  north,  at  Wick  in  Caith- 
ness, and  on  the  shores  of  the  Moray  Frith.  The  principal  deposit  on 
the  Clyde  occurs  at  the  height  of  about  70  feet,  but  a  few  shells  have 


Fig.  110. 
Astarte  borealis. 


Fig.  111. 
Leda  oblong  a. 


Fig.  112.  Fig.  113.  Fig.  114.  Fig.  115. 

Saxicava  rugosa.  Pecten  i&landicus.       Natica  clausa.  Troplion  clathratum. 

Northern  shells  common  in  the  drift  of  the  Clyde,  in  Scotland. 

been  traced  in  it  as  high  as  554  feet  above  the  sea.  Although  a  proper 
tfion  of  between  85  or  90  in  100  of  the  imbedded  shells  are  of  recent 
species,  the  remainder  are  unknown ;  and  even  many  which  are  recent 


CH.  XL]  NORFOLK  DRIFT,   ETC.  131 

now  inhabit  more  northern  seas,  where  we  may,  perhaps,  hereafter  find 
living  representatives  of  some  of  the  unknown  fossils.  The  distance  to 
which  erratic  blocks  have  been  carried  southwards  in  Scotland,  and  the 
course  they  have  taken,  which  is  often  wholly  independent  of  the  present 
position  of  hill  and  valley,  favors  the  idea  that  ice-rafts  rather  than  gla- 
ciers were  in  general  the  transporting  agents.  The  Grampians  in  For- 
farshire  and  in  Perthshire  are  from  3000  to  4000  feet  high.  To  the 
southward  lies  the  broad  and  deep  valley  of  Strathmore,  and  to  the 
south  of  this  again  rise  the  Sidlaw  Hills*  to  the  height  of  1500  feet  and 
upwards.  On  the  highest  summits  of  this  chain,  formed  of  sandstone 
and  shale,  and  at  various  elevations,  are  found  huge  angular  fragments 
of  mica-schist,  some  3  and  others  15  feet  in  diameter,  which  have  been 
conveyed  for  a  distance  of  at  least  15  miles  from  the  nearest  Grampian 
rocks  from  which  they  could  have  been  detached.  Others  have  been 
left  strewed  over  the  bottom  of  the  large  intervening  vale  of  Strath- 
more. 

Still  farther  south  on  the  Pentland  Hills,  at  the  height  of  1100  feet 
above  the  sea,  Mr.  Maclaren  has  observed  a  fragment  of  mica-schist 
weighing  from  8  to  10  tons,  the  nearest  mountain  composed  of  this  for- 
mation being  50  miles  distant.f 

The  testaceous  fauna  of  the  boulder  period,  in  Scotland,  England,  and 
Ireland,  has  been  shown  by  Prof.  E.  Forbes  to  contain  a  much  smaller 
number  of  species  than  that  now  belonging  to  the  British  seas,  and  to 
have  been  also  much  less  rich  in  species  than  the  Older  Pliocene  fauna 
of  the  crag  which  preceded  it.  Yet  the  species  are  nearly  all  of  them 
now  living  either  in  the  British  or  more  northern  seas,  the  shells  of  more 
arctic  latitudes  being  the  most  abundant  and  the  most  wide  spread 
throughout  the  entire  area  of  the  drift  from  north  to  south. 

This  extensive  range  of  the  fossils  can  by  no  means  be  explained  by 
imagining  the  mollusca  of  the  drift  to  have  been  inhabitants  of  a  deep 
sea,  where  a  more  uniform  temperature  prevailed.  On  the  contrary, 
many  species  were  littoral,  and  others  belonged  to  a  shallow  sea,  not 
above  100  feet  deep,  and  very  few  of  them  lived,  according  to  Prof.  E. 
Forbes,  at  greater  depths  than  300  feet. 

From  what  was  before  stated  it  will  appear  that  the  boulder  formation 
displays  almost  everywhere,  in  its  mineral  ingredients,  a  strange  hetero- 
geneous mixture  of  the  mins  of  adjacent  lands,  with  stones  both  angular 
and  rounded,  which  have  come  from  points  often  very  remote.  Thus  we 
find  it  in  our  eastern  counties,  as  in  Norfolk,  Suffolk,  Cambridge,  Hunt- 
ingdon, Bedford,  Hertford,  Essex,  and  Middlesex,  containing  stones  from 
the  Silurian  and  Carboniferous  strata,  and  from  the  lias,  oolite,  and  chalk, 
all  with  their  peculiar  fossils,  together  with  trap,  syenite,  mica-schist, 
granite,  and  other  crystalline  rocks.  A  fine  example  of  this  singular 
mixture  extends  to  the  very  suburbs  of  London,  being  seen  on  the 
summit  of  Muswell  Hill,  Highgate.  But  south  of  London  the  northern 

*  See  above,  section,  p.  48.  f  Geol.  of  Fife,  <fcc.  p.  220. 


132 


NORFOLK  DRIFT  AND 


[Cn.  Xi 


drift  is  wanting,  as,  for  example,  in  the  Wealds  of  Surrey,  Kent,  and 
Sussex. 

Norfolk  drift. — The  drift  can  nowhere  be  studied  more  advantageous- 
ly in  England  than  in  the  cliffs  of  the  Norfolk  coast  between  Happisburgh 
and  Croiner.  Vertical  sections,  having  an  ordinary  height  of  from  50  to 
70  feet,  are  there  exposed  to  view  for  a  distance  of  about  20  miles.  The 
name  of  diluvium  was  formerly  given  to  it  by  those  who  supposed  it  to 
have  been  produced  by  the  violent  action  of  a  sudden  and  transient 
deluge,  but  the  term  drift  has  been  substituted  by  those  who  reject  this 
hypothesis.  Here,  as  elsewhere,  it  consists  for  the  most  part  of  clay, 
loam,  and  sand,  in  part  stratified,  in  part  devoid  of  stratification.  Peb- 
bles, together  with  some  large  boulders  of  granite,  porphyry,  green- 
stone, lias,  chalk,  and  other  transported  rocks,  are  interspersed,  especially 
through  the  till.  That  some  of  the  granitic  and  other  fragments  came 
from  Scandinavia  I  have  no  doubt,  after  having  myself  traced  the  course 
of  the  continuous  stream  of  blocks  from  Norway  and  Sweden  to  Den- 
mark, and  across  the  Elbe,  through  Westphalia,  to  the  borders  of  Hol- 
land. We  need  not  be  surprised  to  find  them  reappear  on  our  eastern 
coast,  between  the  Tweed  and  the  Thames,  regions  not  half  so  remote 
from  parts  of  Norway  as  are  many  Russian  erratics  from  the  sources 
whence  they  came. 

White  chalk  rubble,  unmixed  with  foreign  matter,  and  even  huge 
fragments  of  solid  chalk,  also  occur  in  many  localities  in  these  Norfolk 
cliffs.  No  fossils  have  been  detected  in  this  drift,  which  can  positively 
be  referred  to  the  era  of  its  accumulation  ;  but  at  some  points  it  overlies 
a  freshwater  formation  containing  recent  shells,  and  at  others  it  is  blended 
with  the  same  in  such  a  manner  as  to  force  us  to  conclude  that  both  were 
contemporaneously  deposited. 


Fig.  116. 


Gravel 


The  shaded  portion  consists  of  Freshwater  beds. 
Intercalation  of  freshwater  beds  and  of  boulder  clay  and  sand  at  Mundesley. 

This  interstratification  is  expressed  in  the  annexed  figure,  the  dark  mass 
indicating  the  position  of  the  freshwater  beds,  which  contain  much  vege« 

Fig.  117. 


Paludina  marginata,  Michaud.    (P.  minuta,  Strickland.) 
The  middle  figure  is  of  the  natural  size. 


CH.  XL] 


ASSOCIATED   FRESHWATER  STRATA. 


133 


table  matter,  and  are  divided  into  thin  layers.  The  imbedded  shells  be- 
long to  the  genera  Planorbis,  Lymnea,  Paludina,  Uhio,  Cyclas,  and 
others,  all  of  British  species,  except  a  minute  Paludina,  now  inhabiting 
France.  (See  fig.  117.) 

The  Cyclas  (fig.  118)  is  merely  a  remarkable  variety  of  the  common 
English  species.     The  scales  and  teeth  of  fish  of  the  genera  Pike,  Perch, 

Fig.  118. 


Cyclas  (Pisidiwri)  amnica,  var.  ? 
The  two  middle  figures  are  of  the  natural  size. 

Roach,  and  others,  accompany  these  shells  ;  but  the  species  are  not  con- 
sidered by  M.  Agassiz  to  be  identical  with  known  British  or  European 
kinds. 

The  series  of  formations  in  the  cliffs  of  eastern  Norfolk,  now  under 
consideration,  beginning  with  the  lowest,  is  as  follows : — First,  chalk  ; 
secondly,  patches  of  a  marine  tertiary  formation,  called  the  Norwich 
Crag,  hereafter  to  be  described ;  thirdly,  the  freshwater  beds  already 
mentioned  ;  and  lastly,  the  drift.  Immediately  above  the  chalk,  or  crag, 
when  that  is  present,  is  found  here  and  there  a  buried  forest,  or  a  stra- 
tum in  which  the  stools  and  roots  of  trees  stand  in  their  natural  position, 
the  trunks  having  been  broken  short  off  and  imbedded  with  their 
branches  and  leaves.  It  is  very  remarkable  that  the  strata  of  the  over- 
lying boulder  formation  have  often  undergone  great  derangement  at 
points  where  the  subjacent  forest-bed  and  chalk  remain  undisturbed. 
There  are  also  cases  where  the  upper  portion  of  the  boulder  deposit  has 
been  greatly  deranged,  while  the  lower  beds  of  the  same  have  continued 
horizontal.  Thus  the  annexed  section  (fig.  119)  represents  a  cliff  about 


Fig.  119. 


Gravel 


Cliff  50  feet  high  between  Bacton  Gap  and  Mundesley. 

50  feet  high,  at  the  bottom  of  which  is  till,  or  unstratified  clay,  contain- 
ing boulders  having  an  even  horizontal  surface,  on  which  repose  con- 
formably beds  of  laminated  clay  and  sand  about  5  feet  thick,  which,  in 
their  turn,  are  succeeded  by  vertical,  bent,  and  contorted  layers  of  sand 
and  loam  20  feet  thick,  the  whole  being  covered  by  flint  gravel.  Now 
the  curves  of  the  variously  colored  beds  of  loose  sand,  loam,  and  pebbles 


134: 


MASSES   OF   CHALK  IN  DKIFT. 


[Cn.  XI, 


are  so  complicated  that  not  only  may  we  sometimes  find  portions  of 
them  which  maintain  their  verticality  to  a  height  of  10  or  15  feet,  but 
they  have  also  been  folded  upon  themselves  in  such  a  manner  that  con- 
tinuous layers  might  be  thrice  pierced  in  one  perpendicular  boring. 

At  some  points  there  is  an  apparent  folding  of  the  beds  round  a  cen 
tral  nucleus,  as  at  a,  fig  120,  where  the  strata  seem  bent  round  a  small 

Fig.  121 


Fig.  120. 


Folding  of  the  strata  between  East 
and  West  Kunton. 


Section  of  concentric  beds  west  of  Oromer. 

1.  Blue  clay.  8.  Yellow  Sand. 

2.  White  sand.  4.  Striped  loam  and  clay. 

5.  Laminated  blue  clay. 


mass  of  chalk ;  or,  as  in  fig.  121,  where  the  blue  clay,  No.  1,  is  in  the 
centre ;  and  where  the  other  strata,  2,  3,  4,  5,  are  coiled  round  it ;  the 
entire  mass  being  20  feet  in  perpendicular  height.  This  appearance  of 
concentric  arrangement  around  a  nucleus  is,  nevertheless,  delusive,  being 
produced  by  the  intersection  of  beds  bent  into  a  convex  shape  ;  and  that 
which  seems  the  nucleus  being,  in  fact,  the  innermost  bed  of  the  series, 
which  has  become  partially  visible  by  the  removal  of  the  protuberant 
portions  of  the  outer  layers. 

To  the  north  of  Cromer  are  other  fine  illustrations  of  contorted  drift 
reposing  on  a  floor  of  chalk  horizontally  stratified  and  having  a  level  sur- 
face. These  phenomena,  in  themselves  sufficiently  difficult  of  explanation, 
are  rendered  still  more  anomalous  by  the  occasional  inclosure  in  the  drift 
of  huge  fragments  of  chalk  many  yards  in  diameter.  One  striking  in- 
stance occurs  west  of  Sherringham,  where  an  enormous  pinnacle  of  chalk, 
between  70  and  80  feet  in  height,  is  flanked  on  both  sides  by  vertical 
layers  of  loam,  clay,  and  gravel.  (Fig.  122.) 

This  chalky  fragment  is  only  one  of  many  detached  masses  which  have 
been  included  in  the  drift,  and  forced  along  with  it  into  their  present 
position.  The  level  surface  of  the  chalk  in  situ  (d)  may  be  traced  for 
miles  along  the  coast,  where  it  has  escaped  the  violent  movements  to 
which  the  incumbent  drift  has  been  exposed.* 

We  are  called  upon,  then,  to  explain  how  any  force  can  have  been 
exerted  against  the  upper  masses,  so  as  to  produce  movements  in  which 
the  subjacent  strata  have  not  participated.  It  may  be  answered  that,  it 

*  For  a  full  account  of  the  drift  of  East  Norfolk,  see  a  paper  by  the  author 
Phil.  Mag.  No.  104,  May,  1840. 


On.  XI.] 


MASSES   OF   CHALK   IN  DRIFT. 
Fig.  122. 


135 


Included  pinnacle  of  chalk  at  Old  Hythe  point,  west  of  Sherringham. 
d.  Chalk  with  regular  layers  of  chalk  flints. 

c.  Layer  called  "the  pan,"  of  loose  chalk,  flints,  and  marine  shells  of  recent 
species,  cemented  by  oxide  of  iron. 

we  conceive  the  till  and  its  boulders  to  have  been  drifted  to  their  present 
place  by  ice,  the  lateral  pressure  may  have  been  supplied  by  the  strand- 
ing of  ice-islands.  We  learn  from  the  observations  of  Messrs.  Dease  and 
Simpson  in  the  polar  regions,  that  such  islands,  when  they  run  aground, 
push  before  them  large  mounds  of  shingle  and  sand.  It  is  therefore 
probable  that  they  often  cause  great  alterations  in  the  arrangement  of 
pliant  and  incoherent  strata  forming  the  upper  part  of  shoals  or  sub- 
merged banks,  the  inferior  portions  of  the  same  remaining  unmoved. 
Or  many  of  the  complicated  curvatures  of  these  layers  of  loose  sand  and 
gravel  may  have  been  due  to  another  cause,  the  melting  on  the  spot  of 
icebergs  and  coast-ice  in  which  successive  deposits  of  pebbles,  sand,  ice, 
snow,  and  mud,  together  with  huge  masses  of  rock  fallen  from  cliffs,  may 
have  become  interstratified.  Ice-islands  so  constituted  often  capsize  when 
afloat,  and  gravel  once  horizontal  may  have  assumed,  before  the  associa- 
ted ice  was  melted,  an  inclined  or  vertical  position.  The  packing  of  ice 
forced  up  on  a  coast  may  lead  to  similar  derangement  in  a  frozen  con- 
glomerate of  sand  or  shingle,  and,  as  Mr.  Trimmer  has  suggested,*  alter- 
nate layers  of  earthy  matter  may  have  sunk  down  slowly  during  the  lique- 
faction of  the  intercalated  ice,  so  as  to  assume  the  most  fantastic  and 
anomalous  positions,  while  the  strata  below,  and  those  afterwards  thrown 
down  above,  may  be  perfectly  horizontal. 

There  is,  however,  still  another  mode  in  which  some  of  these  bendings 
may  have  been  produced.  When  a  railway  embankment  is  thrown 
across  a  marsh  or  across  the  bed  of  a  drained  lake,  we  frequently  find 
that  the  foundation,  consisting  of  peat  and  shell-marl,  or  of  quicksand 
and  mud,  gives  way,  and  sinks  as  fast  as  the  embankment  is  raised  at  the 
top.  At  the  same  time,  there  is  often  seen  at  the  distance  of  many  yards, 
in  some  neighboring  part  of  the  morass,  a  squeezing  up  of  pliant  strata, 
the  amount  of  upheaval  depending  on  the  volume  and  weight  of  rnate- 

*  Quart.  Journ.  Geol.  Soc.  vol.  vii.  p.  22. 


136  BUKIED   FOEEST   IN  NORFOLK.  [Cn.  XL 

rials  heaped  upon  the  embankment.  In  1852  I  saw  a  remarkable  in 
stance  of  such  a  downward  and  lateral  pressure,  in  the  suburbs  of  Boston 
(U.  S.),  near  the  South  Cove.  With  a  view  of  converting  part  of  an  es- 
tuary overflowed  at  high  tide  into  dry  land,  they  had  thrown  into  it  a 
vast  load  of  stones  and  sand,  upwards  of  900,000  cubic  yards  in  volume. 
Under  this  weight  the  mud  had  sunk  down  many  yards  vertically.  Mean- 
while the  adjoining  bottom  of  the  estuary,  supporting  a  dense  growth  of 
salt-water  plants,  only  visible  at  low  tide,  had  been  pushed  gradually  up- 
ward, in  the  course  of  many  months,  so  as  to  project  five  or  six  feet  above 
high-water  mark.  The  upraised  mass  was  bent  into  five  or  six  anticlinal 
folds,  and  below  the  upper  layer  of  turf,  consisting  of  salt-marsh  plants, 
mud  was  seen  above  the  level  of  high  tide,  full  of  sea  shells,  such  as  Mya 
arenaria,  Modiola  plicatula,  Sanguinolaria  fusca,  Nassa  obsoleta,  Natica 
triseriata,  and  others.  In  some  of  these  curved  beds  the  layers  of  shells 
were  quite  vertical.  The  upraised  area  was  75  feet  wide,  and  several  hun- 
dred yards  long.  Were  an  eqaal  load,  melted  out  of  icebergs  or  coast-ice 
thrown  down  on  the  floor  of  a  sea,  consisting  of  soft  mud  and  sand,  similai 
disturbances  and  contortions  might  result  in  some  adjacent  pliant  strata, 
yet  the  underlying  more  solid  rocks  might  remain  undisturbed,  and  newer 
formations,  perfectly  horizontal,  might  be  afterwards  superimposed. 

A  buried  forest  has  been  adverted  to  as  underlying  the  drift  on  the 
coast  of  Norfolk.  At  the  time  when  the  trees  grew,  there  must  have  been 
dry  land  over  a  large  area,  which  was  afterwards  submerged,  so  as  to 
allow  a  mass  of  stratified  and  unstratified  drift,  200  feet  and  more  in 
thickness,  to  be  superimposed.  The  undermining  of  the  cliffs  by  the  sea 
in  modern  times  has  enabled  us  to  demonstrate,  beyond  all  doubt,  the 
fact  of  this  superposition,  and  that  the  forest  was  not  formed  along  the 
present  coast-line.  Its  situation  implies  a  subsidence  of  several  hundred 
feet  since  the  commencement  of  the  drift  period,  after  which  there  must 
have  been  an  upheaval  of  the  same  ground ;  for  the  forest  bed  of  Nor- 
folk is  now  again  so  high  as  to  be  exposed  to  view  at  many  points  at  low 
water ;  and  this  same  upward  movement  may  explain  why  the  till, 
which  is  conceived  to  have  been  of  submarine  origin,  is  now  met  with 
far  inland,  and  on  the  summit  of  hills. 

The  boulder  formation  of  the  west  of  England,  observed  in  Lanca- 
shire, Cheshire,  Shropshire,  Staffordshire,  and  Worcestershire,  contains 
in  some  places  marine  shells  of  recent  species,  rising  to  various  heights, 
from  100  to  350  foot  above  the  sea.  The  erratics  have  come  partly  from 
the  mountains  of  Cumberland,  and  partly  from  those  of  Scotland. 

But  it  is  on  the  mountains  of  North  Wales  that  the  "  Northern  drift," 
with  its  characteristic  marine  fossils,  reaches  its  greatest  altitude.  On 
Moel  Tryfane,  near  the  Menai  Straits,  Mr.  Trimmer  met  with  shells  of 
the  species  commonly  found  in  the  drift  at  the  height  of  1392  feet  above 
the  level  of  the  sea. 

It  is  remarkable  that  in  the  same  neighborhood  where  there  is  evi- 
dence of  so  great  a  submergence  'of  the  land  during  part  of  the  glacial 
period,  we  have  also  the  most  decisive  proofs  yet  discovered  in  the  British 


CH.  XII.]  FOSSIL   REMAINS   IX   DRIFT.  137 

Isles  of  sub-aerial  glaciers.  Dr.  Buckland  published  in  1842  his  reasons  foi 
bolievinor  that  the  Suowdoniau  mountains  in  Caernarvonshire  were  former- 

O 

ly  covered  with  glaciers,  which  radiated  from  the  central  heights  through 
the  seven  principal  valleys  of  that  chain,  where  striae  and  flutings  are  seen 
on  the  polished  rocks  directed  towards  as  many  different  points  of  the 
compass.  He  also  described  the  "  moraines"  of  the  ancient  glaciers,  and 
the  rounded  "  bosses"  or  small  flattened  domes  of  polished  rock,  such  as 
the  action  of  moving  glaciers  is  known  to  produce  in  Switzerland,  when 
gravel,  sand,  and  boulders,  underlying  the  ice,  are  forced  along  over  a 
foundation  of  hard  stone.  Mr.  Darwin,  and  subsequently  Prof.  Ramsay, 
have  confirmed  Dr.  Buckland's  views  in  regard  to  these  Welsh  glaciers. 
Nor  indeed  was  it  to  be  expected  that  geologists  should  discover  proofs  of 
icebergs  having  abounded  in  the  area  now  occupied  by  the  British  Isles 
in  the  Pleistocene  period  without  sometimes  meeting  with  the  signs  of 
contemporaneous  glaciers  which  covered  hills  even  of  moderate  elevation 
between  the  50th  and  60th  degrees  of  latitude. 

In  Ireland  the  "  drift"  exhibits  the  same  general  characters  and  fossil  re- 
mains as  in  Scotland  and  England ;  but  in  the  southern  part  of  that  island, 
Prof.  E.  Forbes  and  Capt.  James  found  in  it  some  shells  which  show  that 
the  glacial  sea  communicated  with  one  inhabited  by  a  more  southern  fauna. 
Among  other  species  in  the  south,  they  mention  at  Wexford  and  elsewhere 
the  occurrence  of  Nucula  Cobboldice  (see  fig.  125,  p.  155)  and  Turritella 
incrassata  (a  crag  fossil) ;  also  a  southern  form  of  Fusus,  and  a  Mitra 
allied  to  a  Spanish  species.* 


CHAPTER  XH. 

Difficulty  of  interpreting  the  phenomena  of  drift  before  the  glacial  hypothesis  was 
adopted — Effects  of  intense  cold  in  augmenting  the  quantity  of  alluvium—- 
Analogy  of  erratics  and  scored  rocks  in  North  America  and  Europe — Bayfield 
on  shells  in  drift  of  Canada — Great  subsidence  and  re-elevation  of  land  from  the 
sea,  required  to  account  for  glacial  appearances — Why  organic  remains  so  rare 
in  northern  drift — Mastodon  giganteus  in  United  States — Many  shells  and  some 
quadrupeds  survived  the  glacial  cold — Alps  an  independent  centre  of  dispersion 
of  erratics — Alpine  blocks  on  the  Jura — Whether  transported  by  glaciers  or 
floating  ice — Recent  transportation  of  erratics  from  the  Andes  to  Chiloe — Me- 
teorite in  Asiatic  drift. 

IT  will  appear  from  what  was  said  in  the  last  chapter  of  the  marine 
shells  characterizing  the  boulder  formation,  that  nine-tenths  or  more  of 
them  belong  to  species  still  living.  The  superficial  position  of  "  the  drift" 
is  in  perfect  accordance  with  its  imbedded  organic  remains,  leading  us  to 
refer  its  origin  to  a  modern  period.  If,  then,  we  encounter  so  much  dif- 
ficulty in  the  interpretation  of  monuments  relating  to  times  so  near  our 
own — if  in  spite  of  their  recent  date  they  are  involved  in  so  much  ob- 
scurity— the  student  may  ask,  not  without  reasonable  alarm,  how  we  can 
hope  to  decipher  the  records  of  remoter  ages. 

*  Forbes,  Memoirs  of  Geol.  Survey  of  Great  Britain,  voL  i.  p.  377. 


138  GLACIAL  PHENOMENA  [Ca  Xll 

To  remove  from  the  mind  as  far  as  possible  this  natural  feeling  oi 
discouragement,  I  shall  endeavor  in  this  chapter  to  prove  that  what 
seems  most  strikingly  anomalous,  in  the  "  erratic  formation,"  as  some 
call  it,  is  really  the  result  of  that  glacial  action  which  has  already  been 
alluded  to.  If  so,  it  was  to  be  expected  that  so  long  as  the  true  origin 
of  so  singular  a  deposit  remained  undiscovered,  erroneous  theories  and 
terms  would  be  invented  in  the  effort  to  solve  the  problem.  These 
inventions  would  inevitably  retard  the  reception  of  more  correct  views 
which  a  wider  field  of  observation  might  afterwards  suggest. 

The  term  "  diluvium"  was  for  a  time  the  popular  name  of  the  boul- 
der formation,  because  it  was  referred  by  some  to  the  deluge,  while 
others  retained  the  name  as  expressive  of  their  opinion  that  a  series 
of  diluvial  waves  raised  by  hurricanes  and  storms,  or  by  earthquakes,  or 
by  the  sudden  upheaval  of  land  from  the  bed  of  the  sea,  had  swept  over 
the  continents,  carrying  with  them  vast  masses  of  mud  and  heavy 
stones,  and  forcing  these  stones  over  rocky  surfaces  so  as  to  polish  and 
imprint  upon  them  long  furrows  and  stria3. 

But  no  explanation  was  offered  why  such  agency  should  have  been 
developed  more  energetically  in  modern  times  than  at  former  periods  of 
the  earth's  history,  or  why  it  should  be  displayed  in  its  fullest  intensity 
in  northern  latitudes ;  for  it  is  important  to  insist  on  the  fact,  that  the 
boulder  formation  is  a  northern  phenomenon.  Even  the  southern  ex- 
tension of  the  drift,  or  the  large  erratics  found  in  the  Alps  and  the 
surrounding  lands,  especially  their  occurrence  round  the  highest  parts  of 
the  chain,  offers  such  an  exception  to  the  general  rule  as  confirms  the 
glacial  hypothesis ;  for  it  shows  that  the  transportation  of  stony  frag- 
ments to  great  distances,  and  the  striation,  polishing,  and  grooving  of 
solid  floors  of  rock,  are  here  again  intimately  connected  with  accumula- 
tions of  perennial  snow  and  ice. 

That  there  is  some  intimate  connection  between  a  cold  or  northern 
climate  and  the  various  geological  appearances  now  commonly  called 
glacial,  cannot  be  doubted  by  any  one  who  has  compared  the  countries 
bordering  the  Baltic  with  those  surrounding  the  Mediterranean.  The 
smoothing  and  striation  of  rocks  and  erratics  are  traced  from  the  sea- 
shore to  the  height  of  3000  feet  above  the  level  of  the  Baltic,  whereas 
such  phenomena  are  wholly  wanting  in  countries  bordering  the  Mediter- 
ranean ;  and  their  absence  is  still  more  marked  in  the  equatorial  parts  of 
Asia,  Africa,  and  America  ;  but  when  we  cross  the  southern  tropic,  and 
reach  Chili  and  Patagonia,  we  again  encounter  the  boulder  formation, 
between  the  latitude  41°  S.  and  Cape  Horn,  with  precisely  the  same 
characters  which  it  assumes  in  Europe.  The  evidence  as  to  climate 
derived  from  the  organic  remains  of  the  drift  is,  as  we  have  seen,  in 
perfect  harmony  with  the  conclusions  above  alluded  to,  the  former  habits 
of  the  species  of  mollusca  being  accurately  ascertainable,  inasmuch  as 
they  belong  to  species  still  living,  and  known  to  have  at  present  a  wide 
range  in  northern  seas. 

But  if  we  are  correct  in  assuming  that  the  northern  hemisphere  was 


Cn.  XIL]  OF  NORTHERN  ORIGIN.  139 

considerably  colder  than  now  during  the  period  under  consideration, 
owing  probably  to  the  greater  area  and  height  of  arctic  lands,  and  to  the 
quantity  of  icebergs  which  such  a  geographical  state  of  things  would 
generate,  it  may  be  well  to  reflect  before  we  proceed  farther  on  the  en- 
tire modification  which  extreme  cold  would  produce  in  the  operation  of 
those  causes  spoken  of  in  the  sixth  chapter  as  most  active  in  the  forma- 
tion of  alluvium.  A  large  part  of  the  materials  derived  from  the  detritus 
of  rocks,  which  in  warm  climates  would  go  to  form  deltas,  or  would  be 
regularly  stratified  by  marine  currents,  would,  under  arctic  influences, 
assume  a  superficial  and  alluvial  character.  Instead  of  mud  being  carried 
farther  from  a  coast  than  sand,  and  sand  farther  out  than  pebbles, — instead 
of  dense  stratified  masses  being  heaped  up  in  limited  areas,  along  the  borders 
of  continents, — nearly  the  whole  materials,  whether  coarse  or  fine,  would  be 
conveyed  by  ice  to  equal  distances,  and  huge  fragments,  which  water  alone 
could  never  move,  would  be  borne  for  hundreds  of  miles  without  having 
their  edges  worn  or  fractured ;  and  the  earthy  and  stony  masses,  when 
melted  out  of  the  frozen  rafts,  would  be  scattered  at  random  over  the  sub- 
marine bottom,  whether  on  mountain  tops  or  in  low  plains,  with  scarcely 
any  relation  to  the  inequalities  of  the  ground,  settling  on  the  crests  or 
ridges  of  hills  in  tranquil  water  as  readily  as  in  valleys  and  ravines. 
Occasionally,  in  those  deep  and  uninhabited  parts  of  the  ocean,  never 
reached  by  any  but  the  finest  sediment  in  a  normal  state  of  things,  the 
bottom  would  become  densely  overspread  by  gravel,  mud,  and  boulders. 

In  the  Western  Hemisphere,  both  in  Canada  and  as  far  south  as  the 
40th  and  even  38th  parallel  of  latitude  in  the  United  States,  we  meet 
with  a  repetition  of  all  the  peculiarities  which  distinguish  the  European 
boulder  formation.  Fragments  of  rock  have  travelled  for  great  distances 
from  north  to  south;  the  surface  of  the  subjacent  rock  is  smoothed, 
striated,  and  fluted  ;  unstratified  mud  or  till  containing  boulders  is  asso- 
ciated with  strata  of  loam,  sand,  and  clay,  usually  devoid  of  fossils. 
Where  shells  are  present,  they  are  of  species  still  living  in  northern  seas, 
and  half  of  them  identical  with  those  already  enumerated  as  belonging 
to  European  drift  10  degrees  of  latitude  farther  north.  The  fauna  also  of 
the  glacial  epoch  in  North  America  is  less  rich  in  species  than  that  now 
inhabiting  the  adjacent  sea,  whether  in  the  Gulf  of  St.  Lawrence,  or  off 
the  shores  of  Maine,  or  in  the  Bay  of  Massachusetts.  At  the  southern 
extremity  of  its  course,  moreover,  it  presents  an  analogy  with  the  drift  of 
the  south  of  Ireland,  by  blending  with  a  more  southern  fauna,  as  for 
example  at  Brooklyn  near  New  York,  in  lat.  41°  N.,  where,  according 
to  MM.  Redfield  and  Desor,  Venus  mercenaries  and  other  southern  species 
of  shells  begin  to  occur  as  fossils  in  the  drift. 

The  extension  on  the  American  continent  of  the  range  of  erratics 
during  the  Pleistocene  period  to  lower  latitudes  than  they  reached  in 
Europe,  agrees  well  with  the  present  southward  deflection  of  the  isother- 
mal lines,  or  rather  the  lines  of  equal  winter  temperature.  It  seems  that 
formerly,  as  now,  a  more  extreme  climate  and  a  more  abundant  supply  of 
floating  ice  prevailed  on  the  western  side  of  the  Atlantic. 


140 


DKIFT  SHELLS  IN  CANADA. 


[CE.  XII 


Another  resemblance  between  the  distribution  of  the  drift  fossils  in 
Europe  and  North  America  has  yet  to  be  pointed  out.  In  Norway, 
Sweden,  and  Scotland,  as  in  Canada  and  the  United  States,  the  marine 
shells  are  confined  to  very  moderate  elevations  above  the  sea  (between 
100  and  TOO  feet),  while  the  erratic  blocks  and  the  grooved  and  pol- 
ished surfaces  of  rock  extend  to  elevations  of  several  thousand  feet. 

I  described  in  1839  the  fossil  shells  collected  by  Captain  Bay  field 
from  strata  of  drift  at  Beauport,  near  Quebec,  in  lat.  47°,  and  drew 
from  them  the  inference  that  they  indicated  a  more  northern  climate, 
the  shells  agreeing  in  great  part  with  those  of  Uddevalla  in  Sweden.* 
The  shelly  beds  attain  at  Beauport  and  the  neighborhood  a  height  of 
200,  300,  and  sometimes  400  feet  above  the  sea,  and  dispersed  through 
some  of  them  are  large  boulders  of  granite,  which  could  not  have  been 
propelled  by  a  violent  current,  because  Ine  accompanying  fragile  shells 
are  almost  all  entire.  They  seem,  therefore,  said  Captain  Bayfield, 
writing  in  1838,  to  have  been  dropped  down  from  melting  ice,  like 
similar  stones  which  are  now  annually  deposited  in  the  St.  Lawrence.f 
I  visited  this  locality  in  1842,  and  made  the  annexed  section,  fig.  123, 

'  Fig.  123. 


K.  Mr.  KylarnVs  house. 

h.  Clay  and  sand  of  higher  grounds,  with 

Kaxicava,  &c. 
g.  Gravel  with  boulders. 
/    Mass  of  Saxicava  rugosa,  12  feet  thick, 
c.   Sand  and  loam  with  Mya,  truncata, 

Scalaria  Cfrcenlandica,  &c. 


d.  Drift,  with  boulders  of  syenite,  &c. 

c.  Yellow  sand. 

&.  Laminated  clay,  25  feet  thick. 

A.  Horizontal  lower  Silurian  strata. 

B.  Vallev  re-excavated. 


which  will  give  an  idea  of  the  general  position  of  the  drift  in  Canada 
and  the  United  States.  I  imagine  that  the  whole  of  the  valley  B  was 
once  filled  up  with  the  beds  &,  c,  c?,  e,  /,  which  were  deposited  during  a 
period  of  subsidence,  and  that  subsequently  the  higher  country  (h)  was 
submerged  and  overspread  with  drift.  The  partial  re-excavation  of  B 
took  place  when  this  region  was  again  uplifted  above  the  sea  to  its 
present  height.  Among  the  twenty-three  species  of  fossil  shells  collected 
by  me  from  these  beds  at  Beauport,  all  were  of  recent  northern  species, 
except  one,  which  is  unknown  as  living,  and  may  be  extinct  (see  fig. 
124).  I  also  examined  the  same  formation  farther  up  the  valley  of  the 
St.  Lawrence,  in  the  suburbs  of  Montreal,  where  some  of  the  beds  of 
loam  are  filled  with  great  numbers  of  the  Mytilus  edulis,  or  our  common 
European  mussel,  retaining  both  its  valves  and  purple  color.  This  shelly 
deposit,  containing  Saxicava  rugosa  and  other  characteristic  marine  shells, 

*  Geol.  Trans.  2d  series,  vol.  vi.  p.  1 35.     Mr.  Smith  of  Jordanhill  had  arrived  at 
limilar  conclusions  as  to  climate  from  the  shells  of  the  Scotch  Pleistocene  deposits, 
f  Proceedings  of  Geol.  Soc.  No.  63,  p.  119. 


CH.  XIL]  SUBSIDENCE   IX   DRIFT   PERIOD. 

Fig.  124. 


a 

Astarte  Laurentiana. 
a.  Outside.  &.  Inside  of  right  valve.  c.  Left  valve. 

also  occurs  at  an  elevated  point  on  the  mountain  of  Montreal,  450  feet 
above  the  level  of  the  sea.* 

In  my  account  of  Canada  and  the  United  States,  published  in  1845, 
I  announced  the  conclusion  to  which  I  had  then  arrived,  that  to  explain 
the  position  of  the  erratics  and  the  polished  surfaces  of  rocks,  and  their 
striae  and  flutings,  we  must  assume  first  a  gradual  submergence  of  the 
land  in  North  America,  after  it  had  acquired  its  present  outline  of  hill 
and  valley,  cliff  and  ravine,  and  then  its  re-emergence  from  the  ocean. 
When  the  land  was  slowly  sinking,  the  sea  which  bordered  it  was  covered 
with  islands  of  floating  ice  coming  from  the  north,  which,  as  they 
grounded  on  the  coast  and  on  shoals,  pushed  along  such  loose  materials 
of  sand  and  pebbles  as  lay  strewed  over  the  bottom.  By  this  force  all 
angular  and  projecting  points  were  broken  off,  and  fragments  of  hard 
stone,  frozen  into  the  lower  surface  of  the  ice,  had  power  to  scoop  out 
grooves  in  the  subjacent  solid  rock.  The  sloping  beach,  as  well  as  the 
floor  of  the  ocean,  might  be  polished  and  scored  by  this  machinery ;  but 
no  flood  of  water,  however  violent,  or  however  great  the  quantity  of  de- 
tritus or  size  of  the  rocky  fragments  swept  along  by  it,  could  produce 
such  long,  perfectly  straight  and  parallel  furrows,  as  are  everywhere  visi- 
ble in  the  Niagara  district,  and  generally  in  the  region  north  of  the  40th 
parallel  of  latitude.f 

By  the  hypothesis  of  such  a  slow  and  gradual  subsidence  of  the  land 
we  may  account  for  the  fact  that  almost  everywhere  in  IS".  America  and 
Northern  Europe  the  boulder  formation  rests  on  a  polished  and  furrowed 
surface  of  rock, — a  fact  by  no  means  obliging  us  to  imagine,  as  some 
think,  that  the  polishing  and  grooving  action  was,  as  a  whole,  anterior  in 
date  to  the  transportation  of  the  erratics.  During  the  successive  depres- 
sion of  high  land,  varying  originally  in  height  from  1000  to  3000  feet 
above  the  sea-level,  every  portion  of  the  surface  would  be  brought  down 
by  turns  to  the  level  of  the  ocean,  so  as  to  be  converted  first  into  a  coast- 
line, and  then  into  a  shoal ;  and  at  length,  after  being  well  scored  by  the 
stranding  upon  it,  year  after  year,  of  large  masses  of  coast-ice,  and  occa- 
sional icebergs,  might  be  sunk  to  a  depth  of  several  hundred  fathoms.  By 
the  constant  depression  of  land,  the  coast  would  recede  farther  and  farther 
from  the  successively  formed  zones  of  polished  and  striated  rock,  each  outer 
zone  becoming  in  its  turn  so  deep  under  water  as  to  be  no  longer  grated  upon 
by  the  heaviest  icebergs.  Such  sunken  areas  would  then  simply  serve  as 
receptacles  of  mud,  sand,  and  boulders  dropped  from  melting  ice,  perhaps 

*  Travels  in  IS".  America,  vol.  ii.  p,  141.  f  Ibid.  p.  99,  chap.  xix. 


142  STRIATED   PEBBLES  AND  BOULDERS.  [Ca  XII. 

to  a  depth  scarcely,  if  at  all  inhabited  by  testacea  and  zoophytes.  Mean- 
while, during  the  formation  of  the  unstratified  and  unfossiliferous  mass  in 
deeper  water,  the  smoothing  and  furrowing  of  shoals  and  beaches  would 
still  go  on  elsewhere  upon  and  near  the  coast  in  full  activity.  If  at  length 
the  subsidence  should  cease,  and  the  direction  of  the  movement  of  the  earth's 
crust  be  reversed,  the  sunken  area  covered  with  drift  would  be  slowly  re- 
converted into  land.  The  boulder  deposit,  before  emerging,  would  then  for 
a  time  be  brought  within  the  action  of  the  waves,  tides,  and  currents,  so  that 
its  upper  portion,  being  partially  disturbed,  would  have  its  materials  re- 
arranged and  stratified.  Streams  also  flowing  from  the  land  would  in 
some  places  throw  down  layers  of  sediment  upon  the  till.  In  that  case, 
the  order  of  superposition  will  be,  first  and  uppermost,  sand,  loam,  and 
gravel  occasionally  fossiliferous ;  secondly,  an  unstratified  and  unfossilifer- 
ous mass,  called  till,  for  the  most  part  of  much  older  date  than  the  pre- 
ceding, with  angular  erratics,  or  with  boulders  interspersed ;  and,  thirdly, 
beneath  the  whole,  a  surface  of  polished  and  furrowed  rock.  Such  a 
succession  of  events  seems  to  have  prevailed  very  widely  on  both  sides 
of  the  Atlantic,  the  travelled  blocks  having  been  carried  in  general  from 
the  North  Pole  southwards,  but  mountain  chains  having  in  some  cases 
served  as  independent  centres  of  dispersion,  of  which  the  Alps  present 
the  most  conspicuous  example. 

It  is  by  no  means  rare  to  meet  with  boulders  imbedded  in  drift  which 
are  worn  flat  on  one  or  more  of  their  sides,  the  surface  being  at  the  same 
time  polished,  furrowed,  and  striated.  They  may  have  been  so  shaped 
in  a  glacier  before  they  reached  the  sea,  or  when  they  were  fixed  in  the 
bottom  of  an  iceberg  as  it  ran  aground.  We  learn  from  Mr.  Charles 
Martins  that  the  glaciers  of  Spitzbergen  project  from  the  coast  into  a  sea 
between  100  and  400  feet  deep ;  and  that  numbers  of  striated  pebbles 
or  blocks  are  there  seen  to  disengage  themselves  from  the  overhanging 
masses  of  ice  as  they  melt,  so  as  to  fall  at  once  into  deep  water.* 

That  they  should  retain  such  markings  when  again  upraised  above  the 
sea  ought  not  to  surprise  us,  when  we  remember  that  rippled  sands,  and 
the  cracks  in  clay  dried  between  high  and  low  water,  and  the  foot-tracks 
of  animals  and  rain-drops  impressed  on  mud,  and  other  superficial 
markings,  are  all  found  fossil  in  rocks  of  various  ages. 

On  the  other  hand,  it  is  not  difficult  to  account  for  the  absence  in 
many  districts  of  striated  and  scored  pebbles  and  boulders  in  glacial 
deposits,  for  they  may  have  been  exposed  to  the  action  of  the  waves  on 
a  coast  while  it  was  sinking  beneath  or  rising  above  the  sea.  No  shingle 
on  an  ordinary  sea-beach  exhibits  such  striae,  and  at  a  very  short  distance 
from  the  termination  of  a  glacier  every  stone  in  the  bed  of  the  torrent 
which  gushes  out  from  the  melting  ice  is  found  to  have  lost  its  glacial 
markings  by  being  rolled  for  a  distance  even  of  a  few  hundred  yards. 

The  usual  dearth  of  fossil  shells  in  glacial  clays  well  fitted  to  preserve 
organic  remains  may,  perhaps,  be  owing,  as  already  hinted,  to  the 

*  Bulletin  Soc.  G£ol.  de  France,  torn,  iv  2de  ser.  p.  1121. 


CH.  XII.]  MASTODON    GIGANTEUS.  143 

absence  of  testacea  in  the  deep  sea,  where  the  undisturbed  accumulation 
of  boulders  melted  out  of  coast-ice  and  icebergs  may  take  place.  In  the 
^Egean  and  other  parts  of  the  Mediterranean,  the  zero  of  animal  life, 
according  to  Prof.  E.  Forbes,  is  approached  at  a  depth  of  about  300 
fathoms.  In  tropical  seas  it  would  descend  farther  down,  just  as  vegeta- 
tion ascends  higher  on  the  mountains  of  hot  countries.  Near  the  pole, 
on  the  other  hand,  the  same  zero  would  be  reached  much  sooner  both 
on  the  hills  and  in  the  sea.  If  the  ocean  was  filled  with  floating  bergs, 
and  a  low  temperature  prevailed  in  the  northern  hemisphere  during  the 
glacial  period,  even  the  shallow  part  of  the  sea  might  have  been  unin- 
habitable, or  very  thinly  peopled  with  living  beings.  It  may  also  be 
remarked  that  the  melting  of  ice  in  some  fiords  in  Norway  freshens  the 
water  so  as  to  destroy  marine  life,  and  famines  have  been  caused  in  Ice- 
land by  the  stranding  of  icebergs  drifted  from  the  Greenland  coast, 
which  have  required  several  years  to  melt,  and  have  not  only  injured  the 
hay  harvest  by  cooling  the  atmosphere,  but  have  driven  away  the  fish 
from  the  shore  by  chilling  and  freshening  the  sea. 

If  the  cold  of  the  glacial  epoch  came  on  slowly,  if  it  was  long  before 
it  reached  its  greatest  intensity,  and  again  if  it  abated  gradually,  we  may 
expect  to  find  the  earliest  and  latest  formed  drift  less  barren  of  organic 
remains  than  that  deposited  during  the  coldest  period.  We  may  also 
expect  that  along  the  southern  limits  of  the  drift  during  the  whole  gla- 
cial epoch,  there  would  be  an  intimate  association  of  transported  matter 
of  northern  origin  with  fossil-bearing  sediment,  whether  marine  or  fresh- 
water, belonging  to  more  southern  seas,  rivers,  and  continents. 

That  in  the  United  States,  the  Mastodon  giganteus  was  very  abundant 
after  the  drift  period  is  evident  from  the  fact  that  entire  skeletons  of  this 
animal  are  met  with  in  bogs  and  lacustrine  deposits  occupying  hollows 
in  the  drift.  They  sometimes  occur  in  the  bottom  even  of  small  ponds 
recently  drained  by  the  agriculturist  for  the  sake  of  the  shell  marl.  I  ex- 
amined one  of  these  spots  at  Geneseo  in  the  state  of  New  York,  from 
which  the  bones,  skull,  and  tusk  of  a  Mastodon  had  been  procured  in 
the  marl  below  a  layer  of  black  peaty  earth,  and  ascertained  that  all  the 
associated  freshwater  and  land  shells  were  of  a  species  now  common  in 
the  same  district.  They  consisted  of  several  species  of  Lymnea,  of  Pla- 
norbis  bicarinatus,  Physa  heterostropha,  &c. 

In  1845  no  less  than  six  skeletons  of  the  same  species  of  Mastodon 
were  found  in  Warren  county,  New  Jersey,  6  feet  below  the  surface,  by 
a  farmer  who  was  digging  out  the  rich  mud  from  a  small  pond  which 
he  had  drained.  Five  of  these  skeletons  were  lying  together,  and  a  large 
part  of  the  bones  crumbled  to  pieces  as  soon  as  they  were  exposed  to  the 
air.  But  nearly  the  whole  of  the  other  skeleton,  which  lay  about  10 
feet  apart  from  the  rest,  was  preserved  entire,  and  proved  the  correctness 
of  Cuvier's  conjecture  respecting  this  extinct  animal,  namely,  that  it 
had  twenty  ribs  like  the  living  elephant.  From  the  clay  in  the  interior 
within  the  ribs,  just  where  the  contents  of  the  stomach  might  naturally 
have  been  looked  for,  seven  bushels  of  vegetable  matter  were  extracted, 


144  EXTINCT   MAMMALIA  ABOVE   DRIFT.  [On.  XIL 

I  submitted  some  of  this  matter  to  Mr.  A.  Henfrey,  of  London,  for 
microscopic  examination,  and  he  informs  me  that  it  consists  of  pieces  of 
small  twigs  of  a  coniferous  tree  of  the  Cypress  family,  probably  the  young 
shoots  of  the  white  cedar,  Thuja  occidentalis,  still  a  native  of  North 
America,  on  which  therefore  we  may  conclude  that  this  extinct  Mastodon 
once  fed. 

Another  specimen  of  the  same  quadruped,  the  most  complete  and 
probably  the  largest  ever  found,  was  exhumed  in  1845  in  the  town  of 
Newburg,  New  York,  the  length  of  the  skeleton  being  25  feet,  and  it? 
height  12  feet.  The  anchylosing  of  the  last  two  ribs  on  the  right  side 
afforded  Dr.  John  C.  Warren  a  true  gauge  for  the  space  occupied  by  the 
intervertebrate  substance,  so  as  to  enable  him  to  form  a  correct  estimate 
of  the  entire  length.  The  tusks  when  discovered  were  10  feet  long,  but 
a  part  only  could  be  preserved.  The  large  proportion  of  animal  matter 
in  the  tusk,  teeth,  and  bones  of  some  of  these  fossil  mammalia  is  truly 
astonishing.  It  amounts  in  some  cases,  as  Dr.  C.  T.  Jackson  has  ascer- 
tained by  analysis,  to  27  per  cent.,  so  that  when  all  the  earthy  ingre- 
dients are  removed  by  acids,  the  form  of  the  bone  remains  as  perfect, 
and  the  mass  of  animal  matter  is  almost  as  firm,  as  in  a  recent  bone 
subjected  to  similar  treatment. 

It  would  be  rash,  however  to  infer  from  such  data  that  these  quadru- 
peds were  mired  in  modern  times,  unless  we  use  that  term  strictly  in  a 
geological  sense.  I  have  shown  that  there  is  a  fluviatile  deposit  in  the 
valley  of  the  Niagara,  containing  shells  of  the  genera  Melania,  Lymnea, 
Planorbis,  Valvata,  Cyclas,  Unio,  Helix,  &c.,  all  of  recent  species,  from 
which  the  bones  of  the  great  Mastodon  have  been  taken  in  a  very  perfect 
state.  Yet  the  whole  excavation  of  the  ravine,  for  many  miles  below 
the  Falls,  has  been  slowly  effected  since  that  fluviatile  deposit  was  thrown 
down. 

Whether  or  not,  in  assigning  a  period  of  more  than  30,000  years  for 
the  recession  of  the  Falls  from  Queenstown  to  their  present  site,  I  have 
over  or  under  estimated  the  time  required  for  that  operation,  no  one  can 
doubt  that  a  vast  number  of  centuries  must  have  elapsed  before  so  great 
a  series  of  geographical  changes  were  brought  about  as  have  occurred 
since  the  entombment  of  this  elephantine  quadruped.  The  freshAvater 
gravel  which  incloses  it  is  decidedly  of  much  more  modern  origin  than 
the  drift  or  boulder  clay  of  the  same  region/7' 

Other  extinct  animals  accompany  the  Mastodon  giganteus  in  the  post- 
glacial deposits  of  the  United  States,  among  which  the  Castoroides  ohi- 
oensis,  Foster  and  Wyman,  a  huge  rodent  allied  to  the  beaver,  and  the 
Capybara  may  be  mentioned.  But  whether  the  "loess,"  and  other 
freshwater  and  marine  strata  of  the  Southern  States,  in  which  skeletons 
of  the  same  Mastodon  are  mingled  with  the  bones  of  the  Megatherium, 
Mylodon,  and  Megalonyx,  were  contemporaneous  with  the  drift,  or  were 
of  subsequent  date,  is  a  chronological  question  still  open  to  discussion. 

*  See  Travels  in  N.  America,  vol.  i.  chap,  ii.,  and  Principles  of  Geol.  chap  xiv. 


OH.  XII]  CLIMATE   OF   DEIFT   PERIOD.  145 

It  appears  clear,  however,  from  what  we  know  of  the  tertiary  fossils  oi 
Europe — and  I  believe  the  same  will  hold  true  in  North  America — that 
many  species  of  testacea  and  some  mammalia,  which  existed  prior  to  the 
glacial  epoch,  survived  that  era.  As  European  examples  among  the  warm- 
blooded quadrupeds,  the  Elephas  primigenius  and  Rhinoceros  tichorinus 
may  be  mentioned.  As  to  the  shells,  whether  freshwater,  terrestrial,  or 
marine,  they  need  not  be  enumerated  here,  as  allusion  will  be  made  to 
them  in  the  sequel,  when  the  pliocene  tertiary  fossils  of  Suffolk  are 
described.  The  fact  is  important,  as  refuting  the  hypothesis  that  the 
cold  of  the  glacial  period  was  so  intense  and  universal  as  to  annihilate 
all  living  creatures  throughout  the  globe. 

That  the  cold  was  greater  for  a  time  than  it  is  now  in  certain  parts  of 
Siberia,  Europe,  and  North  America,  will  not  be  disputed ;  but,  before 
we  can  infer  the  universality  of  a  colder  climate,  we  must  ascertain  what 
was  the  condition  of  other  parts  of  the  northern,  and  of  the  whole  south- 
ern, hemisphere  at  the  time  when  the  Scandinavian,  British,  and  Alpine 
erratics  were  transported  into  their  present  position.  It  must  not  be  for- 
gotten that  a  great  deposit  of  drift  and  erratic  blocks  is  now  in  full  pro- 
gress of  formation  in  the  southern  hemisphere,  in  a  zone  corresponding 
in  latitude  to  the  Baltic,  and  to  Northern  Italy,  Switzerland,  France,  and 
England.  Should  the  uneven  bed  of  the  southern  ocean  be  hereafter 
converted  by  upheaval  into  land,  the  hills  and  valleys  will  be  strewed 
over  with  transported  fragments,  some  derived  from  the  antarctic  conti- 
nent, others  from  islands  covered  with  glaciers,  like  South  Georgia,  which 
must  now  be  centres  of  the  dispersion  of  drift,  although  situated  in 
a  latitude,  agreeing  with  that  of  the  Cumberland  mountains  in  Eng- 
land. 

Not  only  are  these  operations  going  on  between  the  45th  and  60th 
parallels  of  latitude  south  of  the  line,  while  the  corresponding  zone  oi 
Europe  is  free  from  ice ;  but,  what  is  still  more  worthy  of  remark,  we 
find  in  the  southern  hemisphere  itself,  only  900  miles  distant  from  South 
Georgia,  where  the  perpetual  snow  reaches  to  the  sea-beach,  lands  covered 
with  forests,  as  in  Terra  del  Fuego.  There  is  here  no  difference  of  lati- 
tude to  account  for  the  luxuriance  of  vegetation  in  one  spot,  and  the 
absolute  want  of  it  in  the  other ;  but  among  other  refrigerating  causes 
in  South  Georgia  may  be  enumerated  the  countless  icebergs  which  float 
from  the  antarctic  zone,  and  which  chill,  as  they  melt,  the  waters  of  the 
ocean,  and  the  surrounding  air,  which  they  fill  with  dense  fogs. 

I  have  endeavored  in  the  "  Principles  of  Geology,"  chapters  7  and  8, 
to  point  out  the  intimate  connection  of  climate  and  the  physical  geogra- 
phy of  the  globe,  and  the  dependence  of  the  mean  annual  temperature, 
not  only  on  the  height  of  the  dry  land,  but  on  its  distribution  in  high 
or  low  latitudes  at  particular  epochs.  If,  for  example,  at  certain  periods 
of  the  past^  the  antarctic  land  was  less  elevated  and  less  extensive  than 
now,  while  that  at  the  north  pole  was  higher  and  more  continuous,  the 
conditions  of  the  northern  and  southern  hemispheres  might  have  been 
the  reverse  of  what  we  now  witness  in  regard  to  climate,  although  the 

10 


146  ALPINE   ERRATICS.  [CH.  XIT 

mountains  of  Scandinavia,  Scotland,  and  Switzerland,  may  have  been 
less  elevated  than  at  present.  But  if  in  both  of  the  polar  regions  a 
considerable  area  of  elevated  dry  land  existed,  such  a  concurrence  of  re- 
frigerating conditions  in  both  hemispheres  might  have  created  for  a  time 
an  intensity  of  cold  never  experienced  since  ;  and  such  probably  was  the 
state  of  things  during  that  period  of  submergence  to  which  I  have 
alluded  in  this  chapter. 

Alpine  erratics. — Although  the  arctic  regions  constitute  the  great 
centre  from  which  erratics  have  travelled  southwards  in  all  directions  in 
Europe  and  North  America,  yet  there  are  some  mountains,  as  I  have 
already  stated,  like  those  of  North  Wales  and  the  Alps,  which  have 
served  as  separate  and  independent  centres  for  the  dispersion  of  blocks. 
In  illustration  of  this  fact,  the  Alps  deserve  particular  attention,  not  only 
from  their  magnitude,  but  because  they  lie  beyond  the  ordinary  limits  ot 
the  "northern  drift"  of  Europe,  being  situated  between  the  44th  and 
47th  degrees  of  north  latitude.  On  the  flanks  of  these  mountains,  and 
on  the  Subalpine  ranges  of  hills  or  plains  adjoining  them,  those  appear- 
ances which  have  been  so  often  alluded  to,  as  distinguishing  or  accom- 
panying the  drift,  between  the  50th  and  7 Oth  parallels  of  north  latitude, 
suddenly  reappear,  to  assume  in  a  more  southern  country  their,  most 
exaggerated  form.  Where  the  Alps  are  highest,  the  largest  erratic  blocks 
have  been  sent  forth,  as,  for  example,  from  the  regions  of  Mont  Blanc 
and  Monte  Rosa,  into  the  adjoining  parts  of  France,  Switzerland,  Austria, 
and  Italy,  while  in  districts  where  the  great  chain  sinks  in  altitude,  as 
in  Carinthia,  Carniola,  and  elsewhere,  no  such  rocky  fragments,  or  a 
few  only,  and  of  smaller  bulk,  have  been  detached  and  transported  to  a 
distance. 

In  the  year  1821,  M.  Venetz  first  announced  his  opinion  that  the 
Alpine  glaciers  must  formerly  have  extended  far  beyond  their  present 
limits,  and  the  proofs  appealed  to  by  him  in  confirmation  of  this  doctrine 
were  afterwards  acknowledged  by  M.  Charpentier,  who  strengthened 
them  by  new  observations  and  arguments,  and  declared,  in  1836,  his 
conviction  that  the  glaciers  of  the  Alps  must  once  have  reached  as  far 
as  the  Jura,  and  have  carried  thither  their  moraines  across  the  great 
valley  of  Switzerland.  M.  Agassiz,  after  several  excursions  in  the  Alps 
with  M.  Charpentier,  and  after  devoting  himself  some  years  to  the  study 
of  glaciers,  published,  in  1840,  an  admirable  description  of  them,  and 
of  the  marks  which  attest  the  former  action  of  great  masses  of  ice  over 
the  entire  surface  of  the  Alps  and  the  surrounding  country.*  He  pointed 
out  that  the  surface  of  every  large  glacier  is  strewed  over  with  gravel 
and  stones  detached  from  the  surrounding  precipices  by  frost,  rain,  light- 
ning, or  avalanches.  And  he  described  more  carefully  than  preceding 
writers  the  long  lines  of  these  stones,  which  settle  on  the  sides  of  the 
glacier,  and  are  called  the  lateral  moraines ;  those  found  at  the  lower 
«nd  of  the  ice  being  called  terminal  moraines.  Such  heaps  of  earth  and 

*  Agassiz,  Eludes  sur  les  Glaciers,  and  Syst6me  Glaciere. 


Cn.  XII.]  MORAINES  OF  GLACIERS.  147 

boulders  every  glacier  pushes  before  it  when  advancing,  and  leaves 
behind  it  when  retreating.  When  the  Alpine  glacier  reaches  a  lower 
and  warmer  situation,  about  3000  or  4000  feet  above  the  sea,  it  melts 
so  rapidly  tjiat,  in  spite  of  the  downward  movement  of  the  mass,  it  can 
advance  no  farther.  Its  precise  limits  are  variable  from  year  to  year, 
and  still  more  so  from  century  to  century ;  one  example  being  on  record 
of  a  recession  of  half  a  mile  in  a  single  year.  We  also  learn  from  M. 
Yenetz,  that  whereas,  between  the  eleventh  and  fifteenth  centuries,  all 
the  Alpine  glaciers  were  less  advanced  than  now,  they  began  in  the 
seventeenth  and  eighteenth  centuries  to  push  forward  so  as  to  cover 
roads  formerly  open,  and  to  overwhelm  forests  of  ancient  growth. 

These  oscillations  enable  the  geologist  to  note  the  marks  which  a  gla- 
cier leaves  behind  it  as  it  retrogrades,  and  among  these  the  most  promi- 
nent, as  before  stated,  are  the  terminal  moraines,  or  mounds  of  tmstrati- 
fied  earth  and  stones,  often  divided  by  subsequent  floods  into  hillocks, 
which  cross  the  valley  like  ancient  earth-works,  or  embankments  made 
to  dam  up  a  river.  Some  of  these  transverse  barriers  were  formerly 
pointed  out  by  Saussure  below  the  glacier  of  the  Rhone,  as  proving  how 
far  it  had  once  transgressed  its  present  boundaries.  On  these  moraines  we 
see  many  large  angular  fragments,  which,  having  been  carried  along  on  the 
surface  of  the  ice,  have  not  had  their  edges  worn  off  by  friction  ;  but  the 
greater  number  of  the  boulders,  even  those  of  large  size,  have  been  well 
rounded,  not  by  the  power  of  water,  but  by  the  mechanical  force  of  the 
ice,  which  has  pushed  them  against  each  other,  or  against  the  rocks 
flanking  the  valley.  Others  have  fallen  down  the  numerous  fissures 
which  intersect  the  glacier,  where,  being  subject  to  the  pressure  of  the 
whole  mass  of  ice,  they  have  been  forced  along,  and  either  well 
rounded  or  ground  down  into  sand,  or  even  the  finest  mud,  of  which 
the  moraine  is  largely  constituted. 

As  the  terminal  moraines  are  the  most  prominent  of  all  the  monu- 
ments left  by  a  receding  glacier,  so  are  they  the  most  liable  to  oblitera- 
tion ;  for  violent  floods  or  debacles  are  often  occasioned  in  the  Alps  by 
the  sudden  bursting  of  what  are  called  glacier-lakes.  These  temporary 
sheets  of  water  are  caused  by  the  damming  up  of  a  river  by  a  glacier 
which  has  increased  during  a  succession  of  cold  seasons,  and  descending 
from  a  tributary  into  the  main  valley,  has  crossed  it  from  side  to  side. 
On  the  failure  of  this  icy  barrier,  the  accumulated  waters  are  let  loose, 
which  sweep  away  and  level  many  a  transverse  mound  of  gravel  and 
loose  boulders  below,  and  spread  their  materials  in  confused  and  irregular 
beds  over  the  river-plain. 

Another  mark  of  the  former  action  of  glaciers,  in  situations  where 
they  exist  no  longer,  is  the  polished,  striated,  and  grooved  surfaces  of 
rocks  already  alluded  to.  Stones  which  lie  underneath  the  glacier  and 
are  pushed  along  by  it,  sometimes  adhere  to  the  ice,  and  as  the  mass 
glides  slowly  along  at  the  rate  of  a  few  inches,  or  at  the  utmost,  two  or 
three  feet,  per  day,  abrade,  groove,  and  polish  the  rock,  -and  the  larger 
blocks  are  reciprocally  grooved  and  polished  by  the  rock  on  their  lower 


148  ALPINE  ERRATICS.  [On.  XII 

sides.  As  the  forces  both  of  pressure  and  propulsion  are  enormous,  the  sand, 
acting  like  emery,  polishes  the  surface ;  the  pebbles,  like  coarse  gravers, 
scratch  and  furrow  it ;  and  the  large  stones  scoop  out  grooves  in  it. 
Another  effect  also  of  this  action,  not  yet  adverted  to,  is  called  "  roches 
moutonnees."  Projecting  eminences  of  rock  are  smoothed  and  worn  into 
the  shape  of  flattened  domes,  where  the  glaciers  have  passed  over  them. 

Although  the  surface  of  almost  every  kind  of  rock,  when  exposed  in  the 
open  air,  wastes  away  by  decomposition,  yet  some  retain  for  ages  their 
polished  and  furrowed  exterior ;  and,  if  they  are  well  protected  by  a  cov- 
ering of  clay  or  turf,  these  marks  of  abrasion  seem  capable  of  enduring 
forever.  They  have  been  traced  in  the  Alps  to  great  heights  above  the 
present  glaciers,  and  to  great  horizontal  distances  beyond  them. 

There  are  also  found,  on  the  sides  of  the  Swiss  valleys,  round  and  deep 
holes,  with  polished  sides,  such  holes  as  waterfalls  make  in  the  solid  rock, 
but  in  places  remote  from  running  waters,  and  where  the  form  of  the 
surface  will  not  permit  us  to  suppose  that  any  cascade  could  ever  have 
existed.  Similar  cavities  are  common  in  hard  rocks,  such  as  gneiss,  in 
Sweden,  where  they  are  called  giant  caldrons,  and  are  sometimes  10 
feet  and  more  in  depth ;  but  in  the  Alps  and  Jura  they  often  pass  into 
spoon-shaped  excavations  and  prolonged  gutters.  We  learn  from  M. 
Agassiz  that  hollows  of  this  form  are  now  cut  out  by  streams  of  water, 
which,  after  flowing  along  the  surface  of  a  glacier,  fall  into  open  fissures  in 
the  ice  and  form  a  cascade.  Here  the  falling  water,  causing  the  gravel 
and  sand  at  the  bottom  to  rotate,  cuts  out  a  round  cavity  in  the  rock.  But 
as  the  glacier  moves  on,  the  cascade  becomes  locomotive,  and  what  would 
otherwise  have  been  a  circular  hole  is  prolonged  into  a  deep  groove.  The 
form  of  the  rocky  bottom  of  the  valley  down  which  the  glacier  is  moving 
causes  the  rents  in  the  ice  and  these  locomotive  cascades  to  be  formed 
again  and  again,  year  after  year,  in  exactly  the  same  spots. 

Another  effect  of  a  glacier  is  to  lodge  a  ring  of  stones  round  the  sum- 
mit of  a  conical  peak  which  may  happen  to  project  through  the  ice.  If 
the  glacier  is  lowered  greatly  by  melting,  these  circles  of  large  angular 
fragments,  which  are  called  "  perched  blocks,"  are  left  in  a  singular  situa- 
tion near  the  top  of  a  steep  hill  or  pinnacle,  the  lower  parts  of  which 
may  be  destitute  of  boulders. 

Alpine  blocks  on  the  Jura. — Now  some  or  all  the  marks  above  enu- 
merated,— the  moraines,  erratics,  polished  surfaces,  domes,  stria3,  cal- 
drons, and  perched  rocks,  are  observed  in  the  Alps  at  great  heights 
above  the  present  glaciers,  and  far  below  their  actual  extremities ;  also 
in  the  great  valley  of  Switzerland,  50  miles  broad ;  and  almost  every- 
where on  the  Jura,  a  chain  which  lies  to  the  north  of  this  valley.  The 
average  height  of  the  Jura  is  about  one-third  that  of  the  Alps,  and  it  is 
now  entirely  destitute  of  glaciers,  yet  it  presents  almost  everywhere 
similar  moraines,  and  the  same  polished  and  grooved  surfaces,  and  water- 
worn  cavities.  The  erratics,  moreover,  which  cover  it,  present  a  phenom- 
enon which  has  astonished  and  perplexed  the  geologist  for  more  than 
half  a  century.  No  conclusion  can  be  more  incontestable  than  that  these 


Cii.  XIL]  ON  THE  JURA.  149 

angular  blocks  of  granite,  gneiss,  and  other  crystalline  formations,  came 
from  the  Alps,  and  that  they  have  been  brought  for  a  distance  of  50 
miles  and  upwards  across  one  of  the  widest  and  deepest  valleys  of  the 
world,  so  that  they  are  now  lodged  on  the  hills  and  valleys  of  a  chain 
composed  of  limestone  and  other  formations,  altogether  distinct  from 
those  of  the  Alps.  Their  great  size  and  angularity,  after  a  journey  of  so 
many  leagues,  has  justly  excited  wonder ;  for  hundreds  of  them  are  as 
large  as  cottages ;  and  one  in  particular,  celebrated  under  the  name  of 
Pierre  a  Bot,  rests  on  the  side  of  a  hill  about  900  feet  above  the  lake 
of  Neufchatel,  and  is  no  less  than  40  feet  in  diameter. 

It  will  be  remarked  that  these  blocks  on  the  Jura  offer  an  exception 
to  the  rule  before  laid  down,  as  applicable  in  general  to  erratics,  since 
they  have  gone  from  south  to  north.  Some  of  the  largest  masses  of 
granite  and  gneiss  have  been  found  to  contain  50,000  and  60,000  cubic  feet 
of  stone,  and  one  limestone  block  at  Devens,  near  Box,  which  has  travelled 
30  miles,  contains  161,000  cubic  feet,  its  angles  being  sharp  and  unworn.* 

Von  Buch,  Escher,  and  Studer  have  shown,  from  an  examination  of 
the  mineral  composition  of  the  boulders,  that  those  on  the  western  Jura, 
near  Neufchatel,  have  come  from  the  region  of  Mont  Blanc  and  the 
Valais;  those  on  the  middle  parts  of  the  Jura  from  the  Bernese  Ober- 
land ;  and  those  on  the  eastern  Jura  from  the  Alps  of  the  small  cantons, 
Glaris,  Schwytz,  Uri,  and  Zug.  The  blocks,  therefore,  of  these  three 
great  districts  have  been  derived  from  parts  of  the  Alps  nearest  to  the 
localities  in  the  Jura  where  we  now  find  them,  as  if  they  had  crossed 
the  great  valley  in  a  direction  at  right  angles  to  its  length :  the  most 
western  stream  having  followed  the  course  of  the  Rhone ;  the  central, 
that  of  the  Aar ;  and  the  eastern,  that  of  the  two  great  rivers,  Reuss 
and  Limmat.  The  non-intermixture  of  these  groups  of  travelled  frag- 
ments, except  near  their  confines,  was  always  regarded  as  most  enig- 
matical by  those  who  adopted  the  opinion  of  Saussure,  that  they  were 
all  whirled  along  by  a  rapid  current  of  muddy  water  rushing  from  the 
Alps. 

M.  Charpentier  first  suggested,  as  before  mentioned,  that  the  Swiss 
glaciers  once  reached  continuously  to  the  Jura,  and  conveyed  to  them 
these  erratics ;  but  at  the  same  time  he  conceived  that  the  Alps  were 
formerly  higher  than  now.  M.  Agassiz,  on  the  other  hand,  instead  of 
introducing  distinct  and  separate  glaciers,  suggested  that  the  whole  valley 
of  Switzerland  might  have  been  filled  with  ice,  and  that  one  great  sheet 
of  it  extended  from  the  Alps  to  the  Jura,  when  the  two  chains  were  of 
the  same  height  as  now  relatively  to  each  other.  Such  an  hypothesis 
labors  under  this  difficulty,  that  the  difference  of  altitude,  when  distributed 
over  a  space  of  50  miles,  gives  an  inclination  of  no  more  than  two  de- 
grees, or  far  less  than  that  of  any  known  glaciers.  It  has,  however,  since 
received  the  able  support  of  Professor  James  Forbes,  in  his  excellent  work 
on  the  Alps,  published  in  1843. 

*  Archiac,  Hist,  des  Progrds,  <fec.  vol.  ii.  p.  249. 


150  EEEATICS  OF  THE  JUEA.  [On.  XII 

In  the  theory  which  I  formerly  advanced,  jointly  with  Mr.  Darwin,* 
it  was  suggested  that  the  erratics  may  have  been  transferred  by  floating 
ice  to  the  Jura,  at  the  time  when  the  greater  part  of  that  chain,  and  the 
whole  of  the  Swiss  valley  to  the  south,  was  under  the  sea.  At  that 
period  the  Alps  may  have  attained  only  half  their  present  altitude,  and 
may  yet  have  constituted  a  chain  as  lofty  as  the  Chilian  Andes,  which, 
in  a  latitude  corresponding  to  Switzerland,  now  send  down  glaciers  to 
the  head  of  every  sound,  from  which  icebergs,  covered  with  blocks  of 
granite,  are  floated  seaward,f  Opposite  that  part  of  Chili  where  the 
glaciers  abound  is  situated  the  island  of  Chiloe,  100  miles  in  length,  with 
a  breadth  of  30  miles,  running  parallel  to  the  continent.  The  channel 
which  separates  it  from  the  main  land  is  of  considerable  depth,  and  25 
miles  broad.  Parts  of  its  surface,  like  the  adjacent  coast  of  Chili,  are 
overspread  with  recent  marine  shells,  showing  an  upheaval  of  the  land 
during  a  very  modern  period;  and  beneath  these  shells  is  a  boulder 
deposit,  in  which  Mr.  Darwin  found  large  travelled  blocks.  One  group 
of  fragments  were  of  granite,  which  had  evidently  come  from  the  Andes, 
while  in  another  place  angular  blocks  of  syenite  were  met  with.  Their 
arrangement  may  have  been  due  to  successive  crops  of  icebergs  issuing 
from  different  sounds,  to  the  heads  of  which  glaciers  descend  from  the 
Andes.  These  icebergs,  taking  their  departure  year  after  year  from  distinct 
points,  may  have  been  stranded  repeatedly,  in  equally  distinct  groups,  in 
bays  or  creeks  of  Chiloe,  and  on  islets  off  the  coast,  so  that  the  stones  trans- 
ported by  them  might  hereafter  appear,  some  on  hills  and  others  in  valleys, 
should  that  country  and  the  bed  of  the  adjacent  sea  be  ever  upheaved.  A 
continuance  in  future  of  the  elevatory  movement,  in  the  region  of  the  Andes 
and  of  Chiloe,  might  cause  the  former  chain  to  rival  the  Alps  in  altitude, 
and  give  to  Chiloe  a  height  equal  to  that  of  the  Jura.  The  same  rise 
might  dry  up  the  channel  between  Chiloe  and  the  main  land,  so  that  it 
would  then  represent  the  great  valley  of  Switzerland.  In  the  course  of 
these  changes,  all  parts  of  Chiloe  and  the  intervening  strait,  having  in 
their  turn  been  a  sea-shore,  may  have  been  polished  and  scratched  by 
coast-ice,  and  by  innumerable  icebergs  running  aground  and  grating  on 
the  bottom. 

If  we  apply  this  hypothesis  to  Switzerland  and  the  Jura,  we  are  by  no 
means  precluded  from  the  supposition  that,  in  proportion  as  the  land 
acquired  additional  height,  and  the  bed  of  the  sea  emerged,  the  Jura 
itself  may  have  had  its  glaciers ;  and  those  existing  in  the  Alps,  which 
had  at  first  extended  to  the  sea,  may,  during  some  part  of  the  period  of 
upheaval,  have  been  prolonged  much  farther  into  the  valleys  than  now. 
At  a  later  period,  when  the  climate  grew  milder,  these  glaciers  may  have 
entirely  disappeared  from  the  Jura,  and  may  have  receded  in  the  Alps 
to  their  present  limits,  leaving  behind  them  in  both  districts  those 
moraines  which  now  attest  the  greater  extension  of  the  ice  in  former  times.J; 

*  See  Elements  of  Geology,  2d  ed.  1841.  f  Darwin's  Journal,  p.  283. 

\  More  recently  Sir  R.  Murchison,  having  revisited  the  Alps,  has  declared  his 


OH.  XII]  METEORITES   IX   DRIFT.  151 

Meteorites  in  drift. — Before  concluding  my  remarks  on  the  northern 
drift  of  the  Old  World,  I  shall  refer  to  a  fact  recently  announced,  the 
discovery  of  a  meteoric  stone  at  a  great  depth  in  the  alluvium  of  North- 
ern Asia. 

Erman,  in  his  Archives  of  Russia  for  1841  (p.  314),  cites  a  very  cir- 
cumstantial account  drawn  up  by  a  Russian  miner  of  the  finding  of  a 
mass  of  meteoric  iron  in  the  auriferous  alluvium  of  the  Altai.  Some 
small  fragments  of  native  iron  were  first  met  with  in  the  gold- washings 
of  Petropawlowsker  in  the  Mrassker  Circle ;  but  though  they  attracted 
attention,  it  was  supposed  that  they  must  have  been  broken  off  from  the 
tools  of  the  workmen.  At  length,  at  the  depth  of  31  feet  5  inches  from 
the  surface,  they  dug  out  a  piece  of  iron  we:ghing  17  J  pounds,  of  a 
steel-gray  color,  somewhat  harder  than  ordinary  iron,  and,  on  analyzing 
it,  found  it  to  consist  of  native  iron,  with  a  small  proportion  of  nickel,  as 
usual  in  meteoric  stones.  It  was  buried  in  the  bottom  of  the  deposit 
where  the  gravel  rested  on  a  flaggy  limestone.  Much  brown  iron  ore, 
as  well  as  gold,  occurs  in  the  same  gravel,  which  appears  to  be  part  of 
that  extensive  auriferous  formation  in  which  the  bones  of  the  mammoth, 
the  Rhinoceros  tichorhinus,  and  other  extinct  quadrupeds  abound.  No 
sufficient  data  are  supplied  to  enable  us  to  determine  whether  it  be  of 
Post-Pliocene  or  Newer  Pliocene  date. 

We  ought  not,  I  think,  to  feel  surprise  that  we  have  not  hitherto 
succeeded  in  detecting  the  signs  of  such  aerolites  in  older  rocks,  for, 
besides  their  rarity  in  our  own  days,  those  which  fell  into  the  sea  (and  it 
is  with  marine  strata  that  geologists  have  usually  to  deal),  being  chiefly 
composed  of  native- iron,  would  rapidly  enter  into  new  chemical  combi- 
nations, the  water  and  mud  being  charged  with  chloride  of  sodium  and 
other  salts.  We  find  that  anchors,  cannon,  and  other  cast-iron  imple- 
ments which  have  been  buried  for  a  few  hundred  years  oft"  our  English 
coast  have  decomposed  in  part  or  entirely,  turning  the  sand  and  gravel 
which  inclosed  them  into  a  conglomerate,  cemented  together  by  oxide  of 
iron.  In  like  manner  meteoric  iron,  although  its  rusting  would  be  some- 
what checked  by  the  alloy  of  nickel,  could  scarcely  ever  fail  to  decompose 
in  the  course  of  thousands  of  years,  becoming  oxide,  sulphuret,  or  car- 
bonate of  iron,  and  its  origin  being  then  no  longer  distinguishable.  The 
greater  the  antiquity  of  rocks, — the  oftener  they  have  been  heated  and 
cooled,  permeated  by  gases  or  by  the  waters  of  the  sea,  the  atmosphere 
or  mineral  springs, — the  smaller  must  be  the  chance  of  meeting  with  a 
mass  of  native  iron  unaltered;  but  the  preservation  of  the  ancient 
meteorite  of  the  Altai,  and  the  presence  of  nickel  in  these  curious  bodies, 
renders  the  recognition  of  them  in  deposits  of  remote  periods  less  hope- 
less than  we  might  have  anticipated. 

opinion  that  "  the  great  granitic  blocks  of  .Mont  Blanc  were  translated  to  the  Jura 
•when  the  intermediate  country  was  under  water:' — Paper  read  to  GeoL  Soc. 
London,  May  30,  1849. 


152  NEWER  PLIOCENE   STRATA.  [Cn.  XIII 


CHAPTER  XIII. 

NEWER    PLIOCENE    STRATA    AND    CAVERN    DEPOSITS. 

Chronological  classification  of  Pleistocene  formations,  why  difficult — Freshwater 
deposits  in  valley  of  Thames — In  Norfolk  cliffs — In  Patagonia — Comparative 
longevity  of  species  in  the  mammalia  and  testacea — Fluvio-marine  crag  of 
Norwich — Newer  Pliocene  strata  of  Sicily — Limestone  of  great  thickness  and 
elevation — Alternation  of  marine  and  volcanic  formations — Proofs  of  slow  accu- 
mulation— Great  geographical  changes  in  Sicily  since  the  living  fauna  and  flora 
began  to  exist — Osseous  breccias  and  cavern  deposits — Sicily — Kirkdale — 
Origin  of  stalactite — Australian  cave-breccias — Geographical  relationship  of  the 
provinces  of  living  vertebrata  and  those  of  the  fossil  species  of  the  Pliocene 
periods — Extinct  struthious  birds  of  New  Zealand — Teeth  of  fossil  quadrupeds. 

HAVING  in  the  last  chapter  treated  of  the  boulder  formation  and  its 
associated  freshwater  and  marine  strata  as  belonging  chiefly  to  the  close 
of  the  Newer  Pliocene  period,  we  may  now  proceed  to  other  deposits  of 
the  same  or  nearly  the  same  age.  It  should,  however,  be  stated  that  it 
is  difficult  to  draw  the  line  of  separation  between  these  modern  forma- 
tions, especially  when  we  are  called  upon  to  compare  deposits  of  marine 
and  freshwater  origin,  or  these  again  with  the  ossiferous  contents  of 
caverns. 

If  as  often  as  the  carcasses  of  quadrupeds  were  buried  in  alluvium 
during  floods,  or  mired  in  swamps,  or  imbedded  in  lacustrine  strata,  a 
stream  of  lava  had  descended  and  preserved  the  alluvial  or  freshwater 
deposits,  as  frequently  happened  in  Auvergne  (see  above,  p.  80),  keeping 
them  free  from  intermixture  with  strata  subsequently  formed,  then  indeed 
the  task  of  arranging  chronologically  the  whole  series  of  mammaliferous 
formations  might  have  been  easy,  even  though  many  species  were 
common  to  several  successive  groups.  But  when  there  have  been 
oscillations  in  the  levels  of  the  land,  accompanied  by  the  widening  and 
deepening  of  valleys  at  more  than  one  period, — when  the  same  surface 
has  sometimes  been  submerged  beneath  the  sea,  after  supporting  forests 
and  land  quadrupeds,  and  then  raised  again,  and  subject  during  each 
change  of  level  to  sedimentary  deposition  and  partial  denudation, — and 
when  the  drifting  of  ice  by  marine  currents  or  by  rivers,  during  an  epoch 
of  intense  cold,  has  for  a  season  interfered  with  the  ordinary  mode  of 
transport,  or  with  the  geographical  range  of  species,  we  cannot  hope 
speedily  to  extricate  ourselves  from  the  confusion  in  which  the  classifica- 
tion of  these  Pleistocene  formations  is  involved. 

At  several  points  in  the  valleyof  the  Thames,  remnants  of  ancient 
fluviatile  deposits  occur,  which  may  differ  considerably  in  age,  although 
the  imbedded  land  and  freshwater  shells  in  each  are  of  recent  species. 
At  Brentford,  for  example,  the  bones  of  the  Siberian  Mammoth,  or 


CH.  XIII.]  DEPOSITS  IN  VALLEY  OF  THAMES.  153 

Elephas  primigenius,  and  the  Rhinoceros  tichorhinus^looth  of  them  quad- 
rupeds of  which  the  flesh  and  hair  have  been  found  preserved  in  the 
frozen  soil  of  Siberia,  occur  abundantly,  with  the  bones  of  an  hippopot- 
amus, aurochs,  short-horned  ox,  red  deer,  reindeer,  and  great  cave-tiger 
or  lion.*  A  similar  group  has  been  found  fossil  at  Maidstone.  in  Kent, 
and  other  places,  agreeing  in  general  specifically  with  the  fossil  bones 
detected  in  the  caverns  of  England.  When  we  see  the  existing  reindeer 
and  an  extinct  hippopotamus  in  the  same  fluviatile  loam,  we  are  tempted 
to  indulge  our  imaginations  in  speculating  on  the  climatal  conditions 
which  could  have  enabled  these  genera  to  coexist  in  the  same  region. 
Wherever  there  is  a  continuity  of  land  from  polar  to  temperate  and  equa- 
torial regions,  there  will  always  be  points  where  the  southern  limit  of  an 
arctic  species  meets  the  northern  range  of  a  southern  species ;  and  if  one 
or  both  have  migratory  habits,  like  the  Bengal  tiger,  the  American  bison, 
the  musk  ox,  and  others,  they  may  each  penetrate  mutually  far  into  the 
respective  provinces  of  the  other.  There  may  also  have  been  several 
oscillations  of  temperature  during  the  periods  which  immediately  pre- 
ceded and  followed  the  more  intense  cold  of  the  glacial  epoch. 

The  strata  bordering  the  left  bank  of  the  Thames  at  Grays  Thurrock, 
in  Essex,  are  probably  of  older  date  than  those  of  Brentford,  although 
the  associated  land  and  freshwater  shells  are  nearly  all,  if  not  all,  identi- 
cal with  species  now  living.  Three  of  the  shells,  however,  are  no  longer 
inhabitants  of  Great  Britain ;  namely,  Paludina  marginata  (fig.  11*7,  p. 
133),  now  living  in  France ;  Unio  littoralis  (fig.  29,  p.  28),  now  inhab- 
iting the  Loire;  and  Cyrena  consobrina  (fig.  26,  p.  28).  The  last- 
mentioned  fossil  (a  recent  Egyptian  shell  of  the  Nile)  is  very  abundant 
at  Grays,  and  deserves  notice,  because  the  genus  Cyrena  is  now  no  longer 
European. 

The  rhinoceros  occurring  in  the  same  beds  (.#.  leptorhinus,  see  fig. 
136,  p.  167),  is  of  a  different  species  from  that  of  Brentford  above  men- 
tioned, and  the  accompanying  elephant  belongs  to  the  variety  called 
Elephas  meridionalis,  which,  according  to  MM.  Owen  and  H.  von  Meyer, 
two  high  authorities,  is  the  same  species  as  the  Siberian  mammoth, 
although  some  naturalists  regard  it  as  distinct.  With  the  above  mam- 
malia is  also  found  the  Hippopotamus  major,  and  what  is  most  remark- 
able in  so  modern  and  northern  a  deposit,  a  monkey,  called  by  Owen 
Macacus  pliocenus. 

The  submerged  forest  already  alluded  to  (p.  137)  as  underlying  the 
drift  at  the  base  of  the  cliffs  of  Norfolk  is  associated  with  a  bed  of  lignite 
and  loam,  in  which  a  great  number  of  fossil  bones  occur,  apparently  of 
the  same  group  as  that  of  Grays,  just  mentioned.  It  has  sometimes 
been  called  "  the  Elephant  bed."  One  portion  of  it,  which  stretches  out 
under  the  sea  at  Happisburgh,  was  overgrown  in  1820  by  a  bank  of 
recent  oysters,  and  there  the  fishermen  dredged  up,  according  to  Wood- 
ward, in  the  course  of  thirteen  years,  together  with  the  oysters,  above 

*  Morris,  Geol.  Soc.  Proceed.  1849. 


164:  FLTJVIO-MARINE  NORWICH  CRAG.  [Cn.  XIII 

2000  mammoths'  grinders.*  Another  portion  of  the  same  continuous 
stratum  has  yielded  at  Bacton,  Cromer,  and  other  places  on  the  coast, 
the  bones  of  a  gigantic  beaver  (Trogontherium  Cuvierii,  Fischer),  as  well 
as  the  ox,  horse,  and  deer,  and  both  species  of  rhinoceros,  R.  tichorhinus 
and  R.  leptorhinus. 

In  studying  these  and  various  other  similar  assemblages  of  fossils,  we 
have  a  good  exemplification  of  the  more  rapid  rate  at  which  the  mam- 
miferous  fauna,  as  compared  to  the  testaceous,  diverges  from  the  recent  type 
when  traced  backwards  in  time.  I  have  before  hinted,  that  the  longevity  of 
species  in  the  class  of  warm-blooded  quadrupeds  is  not  so  great  as  in  that  of 
the  mollusca,  the  latter  having  probably  more  capacity  for  enduring  those 
changes  of  climate  and  other  external  circumstances,  and  those  revolutions 
in  the  organic  world,  which  in  the  course  of  ages  occur  on  the  earth's  surface. 
This  phenomenon  is  by  no  means  confined  to  Europe,  for  Mr.  Darwin 
found  at  Bahia  Blanca,  in  South  America,  lat.  39°  S.,  near  the  northern 
confines  of  Patagonia,  fossil  remains  of  the  extinct  mammiferous  genera 
Megatherium,  Megalonyx,  Toxodon,  and  others,  associated  with  shells, 
almost  all  of  species  already  ascertained  to  be  still  living  in  the  contigu- 
ous sea  ;•}•  the  marine  mollusca,  as  well  as  those  of  rivers,  lakes,  or  the 
land,  having  died  out  more  slowly  than  the  terrestrial  mammalia. 

I  alluded  before  (p.  131)  to  certain  marine  strata  overlying  till  near 
Glasgow,  and  at  other  points  on  the  Clyde,  in  which  the  shells  are  for 
the  most  part  British,  with  an  intermixture  of  some  arctic  species ; 
while  others,  about  a  tenth  of  the  whole,  are  supposed  to  be  extinct. 
This  formation  may  also  be  called  Newer  Pliocene. 

Fluvio-marine  crag  of  Norwich. — At  several  places  within  five  miles 
of  Norwich,  on  both  banks  of  the  Yare,  beds  of  sand,  loam,  and  gravel, 
provincially  termed  "  crag,"  but  of  a  very  different  age  from  the  Suffolk 
crag,  occur,  in  which  there  is  a  mixture  of  marine,  land,  and  freshwater 
shells,  with  ichthyolites  and  bones  of  mammalia.  It  is  clear  that  these 
beds  have  been  accumulated  at  the  bottom  of  the  sea  near  the  mouth  of  a 
river.  They  form  patches  of  variable  thickness,  resting  on  white  chalk, 
and  are  covered  by  a  dense  mass  of  stratified  flint  gravel.  The  surface  of 
the  chalk  is  often  perforated  to  the  depth  of  several  inches  by  the  Pholas 
crispata,  each  fossil  shell  still  remaining  at  the  bottom  of  its  cylindrical 
cavity,  now  filled  up  with  loose  sand  which  has  fallen  from  the  incumbent 
crag.  This  species  of  Pholas  still  exists  and  drills  the  rocks  between  high 
and  low  water  on  the  British  coast.  The  most  common  shells  of  these 
strata,  such  as  Fusus  striatus,  Turritella  terebra,  Cardium  edule,  and 
Cyprina  islandica,  are  now  abundant  in  the  British  seas  ;  but  with  them 
are  some  extinct  species,  such  as  Nucula  Cobboldice  (fig.  125)  and  Tel- 
Una  obliqua  (fig.  126).  Natica  helicoides  (fig.  127)  is  an  example  of  a 
species  formerly  known  only  as  fossil,  but  which  has  now  been  found  living 
in  our  seas. 

Among   the   accompanying   bones   of  mammalia   is    the   Mastodon 

*  Woodward's  Geology  of  Norfolk.          f  Zool.  of  Beagle,  part  1,  pp.  9,  111. 


OH.  XIJL]  NORWICH  CRAG — PLEISTOCENE. 

Fig.  125.  Fig.  126. 


155 


Fig.  127. 


Nvctda  CobMdia. 


Tettina  obliqua. 


Natica  helic&ides, 
Johnston. 


arvernensis*  (see  fig.  135,  p.  165),  a  portion  of  the  upper  jawbone  with 
a  tooth  having  been  found  by  Mr.  Wigham  at  Postwick,  near  Norwich. 
As  this  species  has  also  been  found  in  the  Red  Crag,  both  at  Sutton  and 
at  Felixstow,  and  had  hitherto  been  regarded  as  characteristic  of  forma- 
tions older  than  the  Pleistocene,  it  may  possibly  have  been  washed  out  of 
the  Red  into  the  Norwich  Crag. 

Among  the  bones,  however,  respecting  the  authenticity  of  which  there 
seems  no  doubt,  may  be  mentioned  those  of  the  elephant,  horse,  pig,  deer, 
and  the  jaws  and  teeth  of  field  mice  (fig.  146,  p.  167).  I  have  seen  the 
tusk  of  an  elephant  from  Bramerton  near  Norwich,  to  which  many 
serpulse  were  attached,  showing  that  it  had  lain  for  some  time  at  the 
bottom  of  the  sea  of  the  Norwich  Crag. 

At  Thorpe,  near  Aldborough,  and  at  Southwold,  in  Suffolk,  this  fluvio- 
marine  formation  is  well  exposed  in  the  sea-cliffs,  consisting  of  sand, 
shingle,  loam,  and  laminated  clay.  Some  of  the  strata  there  bear  the 
marks  of  tranquil  deposition,  and  in  one  section  a  thickness  of  40  feet 
is  sometimes  exposed  to  view.  Some  of  the  lamelli-branchiate  shells  have 
both  valves  united,  although  mixed  with  land  and  freshwater  testacea, 
and  with  the  bones  and  teeth  of  elephant,  rhinoceros,  horse,  and  deer. 
Captain  Alexander,  with  whom  I  examined  these  strata  in  1835,  showed 
me  a  bed  rich  in  marine  shells,  in  which  he  had  found  a  large  specimen 
of  the  Fusus  striatus,  filled  with  sand,  and  in  the  interior  of  which  was 
the  tooth  of  a  horse. 

Among  the  freshwater  shells  I  obtained  the  Cyrena  consobrina  (fig.  26, 
p.  28),  before  mentioned,  supposed  to  agree  with  a  species  now  living  in 
the  Nile. 

I  formerly  classed  the  Norwich  Crag  as  older  Pliocene,  conceiving  that 
more  than  a  third  of  the  fossil  testacea  were  extinct ;  but  there  now 
seems  good  reason  for  believing  that  several  of  the  rarer  shells  obtained 
from  these  strata  do  not  really  belong  to  a  contemporary  fauna,  but  have 
been  washed  out  of  the  older  beds  of  the  "  Red  Crag ;"  while  other 
species,  once  supposed  to  have  died  out,  have  lately  been  met  with  living 
in  the  British  seas.  According  to  Mr.  Searles  Wood,  the  total  number 
of  marine  species  does  not  exceed  seventy-six,  of  which  one  tenth  only 
are  extinct.  Of  the  fourteen  associated  freshwater  shells,  all  the  species 
appear  to  be  living.  Strata  containing  the  same  shells  as  those  near 
Norwich  have  been  found  by  Mr.  Bean,  at  Bridlington,  in  Yorkshire. 


Owen,  Brit.  Foss.  Mamm.  271.     Mastodon  longirostris,  Kaup,  see  ibid. 


156  NEWER  PLIOCENE  STRATA.  [On.  XIII. 

Newer  Pliocene  Strata  of  Sicily. — In  no  part  of  Europe  are  the  Newer 
Pliocene  formations  seen  to  enter  so  largely  into  the  structure  of  the 
earth's  crust,  or  to  rise  to  such  heights  above  the  level  of  the  sea,  as  in 
Sicily.  They  cover  nearly  half  the  island,  arid  near  its  centre,  at  Cas- 
trogiovanni,  they  reach  an  elevation  of  3000  feet.  They  consist  princi- 
pally of  two  divisions,  the  upper  calcareous,  the  lower  argillaceous,  both 
of  which  may  be  seen  at  Syracuse,  Girgenti,  and  Castrogiovanni. 

According  to  Philippi,  to  whom  we  are  indebted  for  the  best  account 
of  the  tertiary  shells  of  this  island,  thirty-five  species  out  of  one  hundred 
and  twenty-four  obtained  from  the  beds  in  central  Sicily  are  extinct.  Ot 
the  remainder,  which  still  live,  five  species  are  no  longer  inhabitants  of 
the  Mediterranean.  "When  I  visited  Sicily  in  1828  I  estimated  the  pro- 
portion of  living  species  as  somewhat  greater,  partly  because  I  con- 
founded with  the  tertiary  formation  of  central  Sicily  the  strata  at  the 
base  of  Etna,  and  some  other  localities,  where  the  fossils  are  now  proved 
to  agree  entirely  with  the  present  Mediterranean  fauna. 

Philippi  came  to  the  conclusion,  that  in  Sicily  there  is  a  gradual  pas- 
sage from  beds  containing  70  per  cent,  of  recent  shells,  to  those  in  which 
the  whole  of  the  fossils  are  identical  with  recent  species ;  but  his  tables 
appear  scarcely  to  bear  out  so  important  a  generalization,  several  of  the 
places  cited  by  him  in  confirmation  having  as  yet  furnished  no  more 
than  twenty  or  thirty  species  of  testacea.  The  Sicilian  beds  in  question 
probably  belong  to  about  the  same  period  as  the  Norwich  Crag,  although 
a  geologist,  accustomed  to  see  nearly  all  the  Pleistocene  formations  in 
the  north  of  Europe  occupying  low  grounds  and  very  incoherent  in  tex- 
ture, is  naturally  surprised  to  behold  formations  of  the  same  age  so  solid 
and  stony,  of  such  thickness,  and  attaining  so  great  an  elevation  above 
the  level  of  the  sea. 

The  upper  or  calcareous  member  of  this  group  in  Sicily  consists  in 
some  places  of  a  yellowish-white  stone,  like  the  calcaire  grossier  of  Paris, 
in  others,  of  a  rock  nearly  as  compact  as  marble.  Its  aggregate  thick- 
ness amounts  sometimes  to  700  or  800  feet.  It  usually  occurs  in  regular 
horizontal  beds,  and  is  occasionally  intersected  by  deep  valleys,  such  as 
those  of  Sortino  and  Pentalica,  in  which  are  numerous  caverns.  The 
fossils  are  in  every  stage  of  preservation,  from  shells  retaining  portions 
of  their  animal  matter  and  color,  to  others  which  are  mere  casts. 

The  limestone  passes  downwards  into  a  sandstone  and  conglomerate, 
below  which  is  clay  and  blue  marl,  like  that  of  the  Subappenine  hills, 
from  which  perfect  shells  and  corals  may  be  disengaged.  The  clay 
sometimes  alternates  with  yellow  sand. 

South  of  the  plain  of  Catania  is  a  region  in  which  the  tertiary  beds 
are  intermixed  with  volcanic  matter,  which  has  been  for  the  most  part 
the  product  of  submarine  eruptions.  It  appears  that,  while  the  clay, 
sand,  and  yellow  limestone  before  mentioned  were  in  course  of  deposition 
at  the  bottom  of  the  sea,  volcanoes  burst  out  beneath  the  waters,  like  that 
of  Graham  Island,  in  1831,  and  these  explosions  recurred  again  and  again 
at  distant  intervals  of  time.  Volcanic  ashes  and  sand  were  showered 


CH.  XIII.] 


OF  SICILY. 


157 


down  and  spread  by  the  waves  and  currents  so  as  to  form  strata  of  tuff, 
which  are  found  intercalated  between  beds  of  limestone  and  clay  contain- 
ing marine  shells,  the  thickness  of  the  whole  mass  exceeding  2000  feet. 
The  fissures  through  which  the  lava  rose  may  be  seen  in  many  places 
forming  what  are  called  dikes. 

In  part  of  the  region  above  alluded  to,  as,  for  example,  near  Lentini, 
a  conglomerate  occurs  in  which  I  observed  many  pebbles  of  volcanic 
rocks  covered  by  full  grown  serpulce.  We  may  explain  the  origin  of 
these  by  supposing  that  there  were  some  small  volcanic  islands  which 
may  have  been  destroyed  from  time  to  time  by  the  waves,  as  Graham 
Island  has  been  swept  away  since  1831,  The  rounded  blocks  and 
pebbles  of  solid  volcanic  matter,  after  being  rolled  for  a  time  on  the 
beach  of  such  temporary  islands,  were  carried  at  length  into  some  tran- 
quil part  of  the  sea,  where  they  lay  for  years,  while  the  marine  serpulce 
adhered  to  them,  their  shells  growing  and  covering  their  surface,  as  they 
are  seen  adhering  to  the  shell  figured  in  p.  22.  Finally,  the  bed  of  peb- 
bles was  itself  covered  with  strata  of  shelly  limestone.  At  Vizzini,  a 
town  not  many  miles  distant  to  the  S.  "W.,  I  remarked  another  striking 
proof  of  the  gradual  manner  in  which  these  modern  rocks  were  formed, 
and  the  long  intervals  of  time  which  elapsed  between  the  pouring  out  of 
distinct  sheets  of  lava.  A  bed  of  oysters  no  less  than  20  feet  in  thick- 
ness rests  upon  a  current  of  basaltic  lava.  The  oysters  are  perfectly  iden- 
tifiable with  our  common  eatable  species.  Upon  the  oyster  bed,  again, 
is  superimposed  a  second  mass  of  lava,  together  with  tuff  or  peperino. 
In  the  midst  of  the  same  alternating  igneous  and  aqueous  formations  is 
seen  near  Galieri,  not  far  from  Vizzini,  a  horizontal  bed,  about  a  foot  and 
a  half  in  thickness,  composed  entirely  of  a  common  Mediterranean  coral 
(  Caryophyllia  ccespitosa,  Lam.).  These  corak  stand  erect  as  they  grew ; 

Fig.  128. 


Caryophyllia  ccespitosa,  Lam.         (Cladocora  stellaria,  Milne  Edw.  and  Haime.) 

a.  Stem  with  young  stem  growing  from  its  side. 

a*.  Young  stem  of  same  twice  magnified. 

&.  Portion  of  branch,  twice  magnified,  with  the  base  of  a  lateral  branch ;  the  exterior 

ridges  of  the  main  branch  appearing  through  the  lamellae  of  the  lateral  one. 
c.  Transverse  section  of  same,  proving  by  the  integrity  of  the  main  branch,  that  the 

lateral  one  did  not  originate  in  a  subdivision  of  "the  animal. 
a.  A  branch,  having  at  its  base  another  laterally  united  to  it,  and  two  young  corals  at 

its  upper  part 

«.  A  main  branch,  with  a  full  grown  lateral  one. 
/.    A  perfect  terminal  star. 


158  NEWER  PLIOCENE  STEATA  OF  SICILY.          [On.  X1IL 

and,  after  being  traced  for  hundreds  of  yards,  are  again  found  at  a  cor- 
responding height  on  the  opposite  side  of  the  valley. 

The  corals  are  usually  branched,  but  not  by  the  division  of  the  animals 
as  some  have  supposed,  but  by  the  attachment  of  young  individuals  to 
the  sides  of  the  older  ones ;  and  we  must  understand  this  mode  of  in- 
crease, in  order  to  appreciate  the  time  which  was  required  for  the  building 
up  of  the  whole  bed  of  coral  during  the  growth  of  many  successive  gen- 
erations.* 

Among  the  other  fossil  shells  met  with  in  these  Sicilian  strata,  which 
still  continue  to  abound  in  the  Mediterranean,  no  shell  is  more  conspic- 
uous, from  its  size  and  frequent  occurrence,  than  the  great  scallop,  Pecten 
jacobceus  (see  fig.  129),  now  so  common  in  the  neighboring  seas.  We 
see  this  shell  in  the  calcareous  beds  at  Palermo  in  great  numbers,  in  the 
limestone  at  Girgenti,  and  in  that  which  alternates  with  volcanic  rocks  in 
the  country  between  Syracuse  and  Vizzini,  often  at  great  heights  above 
the  sea. 

Fig.  129. 


Pecten  jacolceus  ;  half  natural  size. 

The  more  we  reflect  on  the  preponderating  number  of  these  recent  shells, 
the  more  we  are  surprised  at  the  great  thickness,  solidity,  and  height 
above  the  sea  of  the  rocky  masses  in  which  they  are  entombed,  and  the 
vast  amount  of  geographical  change  which  has  taken  place  since  their 
origin.  It  must  be  remembered  that,  before  they  began  to  emerge,  the 
uppermost  strata  of  the  whole  must  have  been  deposited  under  water. 
In  order,  therefore,  to  form  a  just  conception  of  their  antiquity,  we  must 
first  examine  singly  the  innumerable  minute  parts  of  which  the  whole  is 
made  up,  the  successive  beds  of  shells,  corals,  volcanic  ashes,  conglomer- 
ates, and  sheets  of  lava ;  and  we  must  afterwards  contemplate  the  time 

*  I  am  indebted  to  Mr.  Lonsdale  for  the  details  above  given  respecting  the 
structure  of  this  coral. 


CH.  XIII]  CAVE   BRECCIAS.  159 

required  for  .the  gradual  upheaval  of  the  rocks,  and  the  excavation  of  the 
valleys.  The  historical  period  seems  scarcely  to  form  an  appreciable  unit 
in  this  computation,  for  we  find  ancient  Greek  temples,  like  those  of 
Girgenti  (Agrigentum),  built  of  the  modern  limestone  of  which  we  are 
speaking,  and  resting  on  a  hill  composed  of  the  same ;  the  site  having 
remained  to  all  appearance  unaltered  since  the  Greeks  first  colonized  the 
island. 

The  modern  geological  date  of  the  rocks  in  this  region  leads  to  another 
singular  and  unexpected  conclusion,  namely,  that  the  fauna  and  flora  of 
a  large  part  of  Sicily  are  of  higher  antiquity  than  the  country  itself, 
having  not  only  flourished  before  the  lands  were  raised  from  the  deep, 
but  even  before  their  materials  were  brought  together  beneath  the  waters. 
The  chain  of  reasoning  which  conducts  us  to  this  opinion  may  be  stated 
in  a  few  words.  The  larger  part  of  the  island  has  been  converted  from 
sea  into  land  since  the  Mediterranean  was  peopled  with  nearly  all  the 
living  species  of  testacea  and  zoophytes.  We  may  therefore  presume 
that,  before  this  region  emerged,  the  same  land  and  river  shells,  and 
almost  all  the  same  animals  and  plants,  were  in  existence  which  now 
people  Sicily ;  for  the  terrestrial  fauna  and  flora  of  this  island  are  pre- 
cisely the  same  as  that  of  other  lands  surrounding  the  Mediterranean. 
There  appear  to  be  no  peculiar  or  indigenous  species,  and  those  which 
are  now  established  there  must  be  supposed  to  have  migrated  from  pre- 
existing lands,  just  as  the  plants  and  animals  of  the  Neapolitan  territory 
have  colonized  Monte  Nuovo,  since  that  volcanic  cone  was  thrown  up  in 
the  sixteenth  century. 

Such  conclusions  throw  a  new  light  on  the  adaptation  of  the  attributes 
and  migratory  habits  of  animals  and  plants  to  the  changes  which  are  un- 
ceasingly in  progress  in  the  physical  geography  of  the  globe.  It  is  clear 
that  the  duration  of  species  is  so  great,  that  they  are  destined  to  outlive 
many  important  revolutions  in  the  configuration  of  the  earth's  surface ; 
and  hence  those  innumerable  contrivances  for  enabling  the  subjects  of  the 
animal  and  vegetable  creation  to  extend  their  range ;  the  inhabitants  of 
the  land  being  often  carried  across  the  ocean,  and  the  aquatic  tribes  over 
great  continental  spaces.  It  is  obviously  expedient  that  the  terrestrial  and 
fluviatile  species  should  not  only  be  fitted  for  the  rivers,  valleys,  plains, 
and  mountains  which  exist  at  the  era  of  their  creation,  but  for  others  that 
are  destined  to  be  formed  before  the  species  shall  become  extinct ;  and, 
in  like  manner,  the  marine  species  are  not  only  made  for  the  deep  and 
shallow  regions  of  the  ocean  existing  at  the  time  when  they  are  called 
into  being,  but  for  tracts  that  may  be  submerged  or  variously  altered  in 
depth  during  the  time  that  is  allotted  for  their  continuance  on  the  globe. 

OSSEOUS  BRECCIAS  AND  DEPOSITS  IN  CAVES  OF  THE  PLIOCENE  PERIOD. 

Sicily. — Caverns  filled  with  marine  breccias,  at  the  base  of  ancient 
sea-cliffs,  have  been  already  mentioned  in  the  sixth  chapter ;  and  it  was 
noticed,  respecting  the  cave  of  San  Ciro,  near  Palermo  (p.  To),  that  upon 


160 


KIRKDALE   CAVE. 


[On.  XIII 


a  bed  of  sand  filled  with  sea-shells,  almost  all  of  recent  species,  rests  a 
breccia  (6,  fig.  93),  composed  of  fragments  of  calcareous  rock,  and  the 
bones  of  animals.  In  the  sand'  at  the  bottom  of  that  cave,  Dr.  Philippi 
found  about  forty-five  marine  shells,  all  clearly  identical  with  recent 
species,  except  two  or  three.  The  bones  in  the  incumbent  breccia  are 
chiefly  those  of  the  mammoth  (E.  primigenius),  with  some  belonging  to 
an  hippopotamus,  distinct  from  the  recent  species,  and  smaller  than  that 
usually  found  fossil.  (See  fig.  137.)  Several  species  of  deer  also,  and, 
according  to  some  accounts,  the  remains  of  a  bear,  were  discovered. 
These  mammalia  are  probably  referable  to  the  Post-Pliocene  period. 

The  Newer  Pliocene  tertiary  limestone  of  the  south  of  Sicily,  already 
described,  is  sometimes  full  of  caverns :  and  the  student  will  at  once  per- 
ceive that  all  the  quadrupeds  of  which  the  remains  are  found  in  the  sta- 
lactite of  these  caverns,  being  of  later  origin  than  the  rocks,  must  be  re- 
ferable to  the  close  of  the  tertiary  epoch,  if  not  of  still  later  date.  The 
situation  of  one  of  these  caves,  in  the  valley  of  Sortino,  is  represented  in 
the  annexed  section. 

Fig.  180. 


&  6   Deposits  in  caves  f  COQtaining  the  remains  of  quadrupeds  for  the  most  part  extinct. 

C.  Limestone  containing  the  remains  of  shells,  of  which  between  70  and  80  per  cent,  are  recent 

England. — In  a  cave  at  Kirkdale,  about  twenty-five  miles  N.  N.  E.  of 
York,  the  remains  of  about  300  hyaenas,  belonging  to  individuals  of  every 
age,  have  been  detected.  The  species  (Hyaena  spelced)  is  extinct,  and  was 
larger  than  the  fierce  Hycena  crocuta  of  South  Africa,  which  it  most  re- 
sembled. Dr.  Buckland,  after  carefully  examining  the  spot,  proved  that 
the  Hyaenas  must  have  lived  there ;  a  fact  attested  by  the  quantity  of 
their  dung,  which,  as  in  the  case  of  the  living  hyaena,  is  of  nearly  the  same 
composition  as  bone,  and  almost  as  durable.  In  the  cave  were  found  the 
remains  of  the  ox,  young  elephant,  hippopotamus,  rhinoceros,  horse,  bear, 
wolf,  hare,  water-rat,  and  several  birds.  All  the  bones  have  the  appear- 
ance of  having  been  broken  and  gnawed  by  the  teeth  of  the  hyaenas ; 
and  they  occur  confusedly  mixed  in  loam  or  mud,  or  dispersed  through 
a  crust  of  stalagmite  which  covers  it.  In  these  and  many  other  cases  it 
is  supposed  that  portions  of  herbivorous  quadrupeds  have  been  dragged 
into  caverns  by  beasts  of  prey,  and  have  served  as  their  food,  an  opinion 
quite  consistent  with  the  known  habits  of  the  living  hyaena. 

No  less  than  thirty-seven  species  of  mammalia  are  enumerated  by  Pro- 
fessor Owen  as  having  been  discovered  in  the  caves  of  the  British  islands, 
of  which  eighteen  appear  to  be  extinct,  while  the  others  still  survive 


CiLXIIL]  AUSTRALIAN   CAVERNS.  161 

in  Europe.  They  were  not  washed  to  the  spots  where  the  fossils  now  oc- 
cur by  a  great  flood ;  but  lived  and  died,  one  generation  after  another,  in 
the  places  where  they  lie  buried.  Among  other  arguments  in  favor  of  this 
conclusion  may  be  mentioned  the  great  numbers  of  the  shed  antlers  of  deer 
discovered  in  caves  and  in  freshwater  strata  throughout  England.* 

Examples  also  occur  of  fissures  into  which  animals  have  fallen  from 
time  to  time,  or  have  been  washed  in  from  above,  together  with  alluvial 
matter  and  fragments  of  rock  detached  by  frost,  forming  a  mass  which 
may  be  united  into  a  bony  breccia  by  stalagmitic  infiltrations.  Fre- 
quently we  discover  a  long  suite  of  caverns  connected  by  narrow  and 
irregular  galleries,  which  hold  a  tortuous  course  through  the  interior  of 
mountains,  and  seem  to  have  served  as  the  subterranean  channels  of 
springs  and  engulfed  rivers.  Many  streams  in  the  Morea  are  now  car- 
rying bones,  pebbles,  and  mud  into  underground  passages  of  this  kind. 
I£  at  some  future  period,  the  form  of  that  country  should  be  wholly 
altered  by  subterranean  movements  and  new  valleys  shaped  out  by 
denudation,  many  portions  of  the  former  channels  of  these  engulfed 
streams  may  communicate  with  the  surface,  and  become  the  dens  of  wild 
beasts,  or  the  recesses  to  which  quadrupeds  retreat  to  die.  Certain  caves 
of  France,  Germany,  and  Belgium,  may  have  passed  successively  through 
these  different  conditions,  and  in  their  last  state  may  have  remained 
open  to  the  day  for  several  tertiary  periods.  It  is  nevertheless  re- 
markable, that  on  the  continent  of  Europe,  as  in  England,  the  fossil 
remains  of  mammalia  belong  almost  exclusively  to  those  of  the  Newer 
Pliocene  and  Post-Pliocene  periods,  and  not  to  the  Miocene  or  Eocene 
epochs,  and  when  they  are  accompanied  by  land  or  river  shells,  these 
agree  in  great  part,  or  entirely,  with  recent  species. 

As  the  preservation  of  the  fossil  bones  is  due  to  a  slow  and  constant 
supply  of  stalactite,  brought  into  the  caverns  by  water  dropping  from  the 
roof,  the  source  and  origin  of  this  deposit  has  been  a  subject  of  curious 
inquiry.  The  following  explanation  of  the  phenomenon  has  been  re- 
cently suggested  by  the  eminent  chemist  Liebig.  On  the  surface  of 
Franconia,  where  the  limestone  abounds  in  caverns,  is  a  fertile  soil,  in 
which  vegetable  matter  is  continually  decaying.  This  mould  or  humus, 
being  acted  on  by  moisture  and  air,  evolves  carbonic  acid  which  is  dis- 
solved by  rain.  The  rain-water,  thus  impregnated,  permeates  the  porous 
limestone,  dissolves  a  portion  of  it,  and  afterwards,  when  the  excess  of 
carbonic  acid  evaporates  in  the  caverns,  parts  with  the  calcareous  matter, 
and  forms  stalactite.  Such  facts  seem  to  imply  that  the  date  of  the  emer- 
gence of  the  district  was  very  modern,  for  stalactite  could  not  begin  to  form 
until  the  emergence  of  the  cavernous  rock,  and  the  land  shells  and  land 
animals  are  usually  imbedded  in  the  lowest  part  of  the  stalactite  deposit. 

Australian  cave-breccias. — Ossiferous  breccias  are  not  confined  to  Eu- 
rope, but  occur  in  all  parts  of  the  globe  ;  and  those  lately  discovered  in 
fissures  and  caverns  in  Australia  correspond  closely  in  character  with 
what  has  been  called  the  bony  breccia  of  the  Mediterranean,  in  which  the 

*  Oweu,  Brit.  Foss.  Mara.  xxvi.  and  Buckland,  Rel.  Dil.  19,  24. 
11 


162 


FOSSILS  IN  AUSTKALIAN  CAVES. 


[On.  XIII 


fragments  of  bone  and  rock  are  firmly  bound  together  by  a  red  ochreous 
cement. 

Some  of  these  caves  have  been  examined  by  Sir  T.  Mitchell  in  the 
Wellington  Valley,  about  210  miles  west  of  Sidney,  on  the  river  Bell, 
one  of  the  principal  sources  of  the  Macquarie,  and  on  the  Macquarie 
itself.  The  caverns  often  branch  off  in  different  directions  through  the 
rock,  widening  and  contracting  their  dimensions,  and  the  roofs  and  floors 
are  covered  with  stalactite.  The  bones  are  often  broken,  but  do  not  seem 
to  be  water-worn.  In  some  places  they  lie  imbedded  in  loose  earth,  but 
they  are  usually  included  in  a  breccia. 

The  remains  found  most  abundantly  are  those  of  the  kangaroo,  of 
which  there  are  four  species,  besides  which  the  genera  JETypsiprymnus, 
Phalangista,  Phascolomys,  and  Dasyurus,  occur.  There  are  also  bones, 
formerly  conjectured  by  some  osteologists  to  belong  to  the  hippopotamus, 
and  by  others  to  the  dugong,  but  which  are  now  referred  by  Mr.  Owen 
to  a  marsupial  genus,  allied  to  the  Wombat. 

In  the  fossils  above  enumerated,  several  species  are  larger  than  the 
largest  living  ones  of  the  same  genera  now  known  in  Australia.  The 
annexed  figure  of  the  right  side  of  a  lower  jaw  of  a  kangaroo  (Macro- 


Fig.  131 


Macropus  atlas,  Owen. 
a.  Permanent  false  molar,  in  the  alveolus. 

pus  atlas,  Owen)  will  at  once  be  seen  to  exceed  in  magnitude  the  cor- 
responding part  of  the  largest  living  kangaroo,  which  is  represented  in 

Fig.  132. 


Lowest  jaw  of  largest  living  species  of  kangaroo. 
(Macropua  major.) 


EXTIXCT  FOSSIL   MAMMALIA.  163 

fig.  132.  In  both  these  specimens  part  of  the  substance  of  the  jaw  has 
been  broken  open,  so  as  to  show  the  permanent  false  molar  (a,  fig.  131) 
concealed  in  the  socket.  From  the  fact  of  this  molar  not  having  been 
cut,  we  learn  that  the  individual  was  young,  and  had  not  shed  its  first 
Fig.  133.  teeth.  In  fig.  133,  a  front  tooth  of  the  same  species  of 
kangaroo,  is  represented. 

Whether  the  breccias,  above  alluded  to,  of  the  Wellington 
Valley,  appertain  strictly  to  the  Pliocene  period  cannot  be 
affirmed  with  certainty,  until  we  are  more  thoroughly 
acquainted  with  the  recent  quadrupeds  of  the  same  dis- 
trict, and  until  we  learn  what  species  of  fossil  land  shells, 
if  any,  are  buried  in  the  deposits  of  the  same  caves. 

The  reader  will  observe  that  all  these  extinct  quadrupeds 
of  Australia  belong  to  the  marsupial  family,  or,  in  other 
words,  that  they  are  referable  to  the  same  peculiar  type  of 
organization  which  now  distinguishes  the  Australian  mam- 
malia from  those  of  other  parts  of  the  globe.  This  fact  is 
cropus.  one  Of  manv  pointing  to  a  general  law  deducible  from  the 
fossil  vertebrate  and  invertebrate  animals  of  the  eras  immediately  ante- 
cedent to  the  human,  namely,  that  the  present  geographical  distribution 
of  organic  forms  dates  back  to  a  period  anterior  to  the  creation  of  ex- 
isting species ;  in  other  words,  the  limitation  of  particular  genera  or 
families  of  quadrupeds,  mollusca,  &c.,  to  certain  existing  provinces  of 
land  and  sea,  began  before  the  species  now  contemporary  with  man  had 
been  introduced  into  the  earth. 

Mr.  Owen,  in  his  excellent  "  History  of  British  Fossil  Mammals,"  has 
called  attention  to  this  law,  remarking  that  the  fossil  quadrupeds  of 
Europe  and  Asia  differ  from  those  of  Australia  or  South  America.  We 
do  not  find,  for  example,  in  the  Europseo- Asiatic  province  fossil  kangaroos 
or  armadillos,  but  the  elephant,  rhinoceros,  horse,  bear,  hyaena,  beaver, 
hare,  mole,  and  others,  which  still  characterize  the  same  continent. 

In  like  manner  in  the  Pampas  of  South  America  the  skeletons  of  Me- 
gatherium, Megalonyx,  Glyptodon,  Mylodon,  Toxodon,  Macrauchenia, 
and  other  extinct  forms,  are  analogous  to  the  living  sloth,  armadillo,  cavy, 
capybara,  and  llama.  The  fossil  quadrumana,  also  associated  with  some 
of  these  forms  in  the  Brazilian  caves,  belong  to  the  Platyrrhine  family  of 
monkeys,  now  peculiar  to  South  America.  That  the  extinct  fauna  of 
Buenos  Ayres  and  Brazil  was  very  modern  has  been  shown  by  its  rela- 
tion to  deposits  of  marine  shells,  agreeing  with  those  now  inhabiting  the 
Atlantic;  and  when  in  Georgia  in  1845,1  ascertained  that  the  Mega- 
therium, Mylodon,  Harlanus  americanus  (Owen),  Equus  curvidens,  and 
other  quadrupeds  allied  to  the  Pampean  type,  were  posterior  in  date  to 
beds  containing  marine  shells  belonging  to  forty-five  recent  species  of  the 
neighboring  sea. 

There  are  indeed  some  cosmopolite  genera,  such  as  the  Mastodon  (a 
genus  of  the  elephant  family),  and  the  horse,  which  were  simultaneously 
represented  by  different  fossil  species  in  Europe,  North  America,  and 


164  EXTINCT  FOSSIL   MAMMALIA.  [Cn.  XIII 

South  America ;  but  these  few  exceptions  can  by  no  means  invalidate 
the  rule  which  has  been  thus  expressed  by  Professor  Owen,  "  that  in  the 
highest  organized  class  of  animals  the  same  forms  were  restricted  to  the 
same  great  provinces  at  the  Pliocene  periods  as  they  are  at  the  pres- 
ent day." 

However  modern,  in  a  geological  point  of  view,  we  may  consider  the 
Pleistocene  epoch,  it  is  evident  that  causes  more  general  and  powerful 
than  the  intervention  of  man  have  occasioned  the  disappearance  of  the 
ancient  fauna  from  so  many  extensive  regions.  Not  a  few  of  the  species 
had  a  wide  range  'r  the  same  Megatherium,  for  instance,  extended  from 
Patagonia  and  the  river  Plata  in  South  America,  between  latitudes  31° 
and  39°  south,  to  corresponding  latitudes  in  North  America,  the  same 
animal  being  also  an  inhabitant  of  the  intermediate  country  of  Brazil, 
where  its  fossil  remains  have  been  met  with  in  caves.  The  extinct  ele- 
phant, likewise,  of  Georgia  (Elephas  primigenius)  has  been  traced  in  a 
fossil  state  northward  from  the  river  Alatamaha,  in  lat.  33°  50'  N.  to  the 
polar  regions,  and  then  again  in  the  eastern  hemisphere  from  Siberia  to 
the  south  of  Europe,  If  it  be  objected  that,  notwithstanding  the  adapta- 
tion of  such  quadrupeds  to  a  variety  of  climates  and  geographical  con- 
ditions, their  great  size  exposed  them  to  extermination  by  the  first  hunter 
tribes,  we  may  observe  that  the  investigations  of  Lund  and  Clausen  in 
the  ossiferous  limestone  caves  of  Brazil  have  demonstrated  that  these 
large  mammalia  were  associated  with  a  great  many  smaller  quadrupeds, 
some  of  them  as  diminutive  as  field  mice,  which  have  all  died  out  together, 
while  the  land  shells  formerly  their  contemporaries  still  continue  to  exist 
in  the  same  countries.  As  we  may  feel  assured  that  these  minute  quad- 
rupeds eould  never  have  been  extirpated  by  man,  especially  in  a  country 
so  thinly  peopled  as  Brazil,  so  we  may  conclude  that  all  the  species,  small 
and  great,  have  been  annihilated  one  after  the  other,  in  the  course  of  in- 
definite ages,  by  those  changes  of  circumstances  in  the  organic  and  inor- 

O         '          •/  O  O 

ganic  world  which  are  always  in  progress,  and  are  capable  in  the  course 
of  time  of  greatly  modifying  the  physical  geography,  climate,  and  all 
other  conditions  on  which  the  continuance  upon  the  earth  of  any  living 
being  must  depend.* 

The  law  of  geographical  relationship  above  alluded  to,  between  the 
living  vertebrata  of  every  great  zoological  province  and  the  fossils  of  the 
period  immediately  antecedent,  even  where  the  fossil  species  are  extinct, 
is  by  no  means  confined  to  the  mammalia.  New  Zealand,  when  first 
examined  by  Europeans,  was  found  to  contain  no  indigenous  land  quad- 
rupeds, no  kangaroos,  or  opossums,  like  Australia ;  but  a  wingless  bird 
abounded  there,  the  smallest  living  representative  of  the  ostrich  family^ 
called  Kivi,  by  the  natives  (Apteryx).  In  the  fossils  of  the  Post-Pliocene 
and  Pleistocene  period  in  this  same  island,  there  is  the  like  absence  of 
kangaroos,  opossums,  wombats,  and  the  rest ;  but  in  their  place  a  pro- 
digious number  of  well-preserved  specimens  of  gigantic  birds  of  the  stru- 
thious  order,  called  by  Owen  Dinornis  and  Palapteryx,  which  are  en- 
*  See  Principles  of  Geology,  chaps,  xli.  to  xliv. 


CH.  XIII.] 


TEETH   OF   FOSSIL  QUADRUPEDS. 


165 


tombed  in  superficial  deposits.  These  genera  comprehended  many  spe- 
cies, some  of  which  were  4,  some  7,  others  9,  and  others  11  feet  in 
height !  It  seems  doubtful  whether  any  contemporary  mammalia  shared 
the  land  with  this  population  of  gigantic  feathered  bipeds. 

To  those  who  have  never  studied  comparative  anatomy  it  may  seem 
scarcely  credible,  that  a  single  bone  taken  from  any  part  of  the  skeleton 
may  enable  a  skilful  osteologist  to  distinguish,  in  many  cases,  the  genus, 
and  sometimes  the  species,  of  quadruped  to  which  it  belonged.  Although 
few  geologists  can  aspire  to  such  knowledge,  which  must  be  the  result  of 
long  practice  and  study,  they  will  nevertheless  derive  great  advantage 
from  learning  what  is  comparatively  an  easy  task,  to  distinguish  the 
principal  divisions  of  the  mammalia  by  the  forms  and  characters  of  their 
teeth.  The  annexed  figures,  all  taken  from  original  specimens,  may  be 
useful  in  assisting  the  student  to  recognize  the  teeth  of  many  genera  most 
frequently  found  fossil  in  the  Newer  Pliocene  and  Post-Pliocene  periods : — 


Fig.  134. 


Elepha*  primigeniu*  (or  Mammoth) ;  molar  of  upper  jaw,  right  side ;  one-third  of  nat  size. 
a.  Grinding  surface.  &.  Side  view. 

Fig.  135. 


Mastodon  arrernemia  (Norwich  Crag,  Postwick,  also  found  in  Bed  Crae,  see  p.  155);  second 
true  molar,  left  side,  upper  jaw ;  grinding  surface,  nat  size.    (See.  p.  155.) 


166 


TEETH  OF  FOSSIL  MAMMALIA. 
Fig.  136.  Fig.  137. 


Khinoceros. 

Rhinoceros  leptorMmis  ;  fos- 
sil from  freshwater  beds  of 
Grays,  Essex  (see  p.  153); 
penultimate  molar,  lower 
jaw,  left  side ;  two-thirds  of 
Qat.  size. 


Hippopotamus. 

Hippopotamus  Penttandi, 
H.  v.  Meyer;  from  cave 
near  Palermo  (see  p.  160) ; 
molar  tooth;  two-thirds 
of  nat.  size. 


Pig. 

8us  scrofa,  Lin.  (common 
pig)  ;  from  shell-marl, 
Forfarshire  ;  posterior 
molar,  lower  jaw,  nat. 
size. 


Fie.  139. 


Fig.  140. 


Horse. 


Equus  cabaUus,  Lin.  (common  horse) ; 
from  the  shell-marl,  Forfarshire  ; 
second  molar,  lower  jaw. 

a.  Grinding  surface,  two-thirds  nat.  size. 

b.  Side  view  of  same,  half  nat.  size. 


Tapir. 

Tapims  America-tins 
recent ;  third  mola 
upper  jaw;  nat.  size. 


Fig.  141. 


Fig.  142. 


a.  &.  Beer. 

Elk  (Cervus  alces,  Lin.);  re- 
cent; molar  of  upper  jaw. 

a.  Grinding  surface. 
I.  Side  view;    two-thirds  of 
nat.  size. 


c.  d.  Ox. 

Ox,  common,  from  shell-marl,  Forfar- 
shire ;  true  molar  upper  jaw  ;  two- 
thirds  nat.  size. 

c.  Grinding  surface. 

d.  Side  view  ;  fangs  uppermost. 


CH.  XIV.]  OLDER   PLIOCENE   FORMATIONS. 

Fig.  143.  Fig.  144. 


167 


Bear, 
a.  Canine  tooth  or  tusk  of  bear  (  Urrns 

spelceus) ;  from  cave  near  Liege. 
&.  Molar  of  left  side,  upper  jaw ;  one 

third  of  nat  size. 

Fig.  145. 


Tiger. 

c.  Canine  tooth  of  tiger  (Fdis  tigrte) ; 

recent. 

d.  Outside  view   of  posterior  molar 

lower  jaw ;  one-third  of  nat.  size. 

Fig.  146. 


UyoRna  spelcea:  second  molar,  left 
side,  lower  jaw ;  nat  size.  Cave 
ofKirkdale.  (See  p.  160.) 


Teeth  of  a  new  species  of  Arvicola  (field  mouse) ;  from  the 

Norwich  Crag.    (See  p.  155.) 
a.  Grinding  surface.  &.  Side  view  of  same. 

c.  Nat  size  of  a  and  &. 

Fig.  147. 


a.  Fourth  molar,  right  side,  lower  jaw.    Megatherium;  Georgia, 
U.  S. ;  one-third  nat  size. 


<L 

Crown  of  same. 


CHAPTER  XIV. 

OLDER  PLIOCENE  AND  MIOCENE  FORMATIONS. 

Strata  of  Suffolk  termed  Red  and  Coralline  Crag — Fossils,  and  proportion  of  re- 
cent species — Depth  of  sea  and  climate — Reference  of  Suffolk  Crag  to  the 
Older  Pliocene  period — Migration  of  many  species  of  shells  southwards  during 
the  glacial  period — Fossil  whales — Antwerp  Crag — Subapennine  beds — Asti, 
Sienna,  Rome  —  Aralo-Caspian  formations  —  Miocene  formations  —  Faluns  of 
Touraine — Depth  of  sea  and  littoral  character  of  fauna — Tropical  climate  im. 
plied  by  the  testacea — Proportion  of  recent  species  of  shells — Faluns  more  an- 
cient than  the  Suffolk  Crag — Miocene  strata  of  Bourdeaux — of  the  Bolderberg 
in  Belgium — of  ISorth  Germany— Vienna  Basin — Piedmont — Molasse  of  Swit- 
zerland— Leaf-beds  of  Mull  in  Scotland— Older  Pliocene  and  Miocene  forma- 
tions in  the  United  States— Sew^lik  Hills  in  India. 

THE  older  Pliocene  strata,  which  next  claim  our  attention,  are  chiefly 
confined,  in  Great  Britain,  to  the  eastern  part  of  the  county  of  Suffolk, 


168  OLDER   PLIOCENE   FORMATIONS.  [On.  XIV 

where,  like  the  Norwich  beds  already  described,  they  are  called  "  Crag,7' 
a  provincial  name  given  particularly  to  those  masses  of  shelly  sand  which 
have  been  used  from  very  ancient  times  in  agriculture,  to  fertilize  soils 
deficient  in  calcareous  matter.  The  relative  position  of  the  "  Red  Crag" 
in  Essex  to  the  London  clay,  may  be  understood  by  reference  to  the  ac- 
companying diagram  (fig.  148). 

Fig.  148. 
Crag.  London  Clay.  Chalk. 


These  deposits,  according  to  Professor  E.  Forbes,  appear  by  their  im- 
bedded shells  to  have  been  formed  in  a  sea  of  moderate  depth,  usually 
from  15  to  25  fathoms,  but  in  some  few  spots  perhaps  deeper.  Yet  they 
cannot  be  called  littoral,  because  the  fauna  is  such  as  may  have  extended 
40  or  50  miles  from  land. 

The  Suffolk  Crag  is  divisible  into  two  masses,  the  upper  of  which  has 
been  termed  the  Red,  and  the  lower  the  Coralline  Crag.*  The  upper 
deposit  consists  chiefly  of  quartzose  sand,  with  an  occasional  intermixture 
of  shells,  for  the  most  part  rolled,  and  sometimes  comminuted.  In  many 
places  fossils  washed  out  of  older  tertiary  strata,  especially  the  London 
Clay,  are  met  with.  The  lower  or  coralline  Crag  is  of  very  limited  ex- 
tent, ranging  over  an  area  about  20  miles  in  length,  and  3  or  4  in  breadth, 
between  the  rivers  Aide  and  Stour.  It  is  generally  calcareous  and  marly 
— a  mass  of  shells,  bryozoa,f  and  small  corals,  passing  occasionally  into  a 
soft  building-stone.  At  Sudbourn,  near  Oxford,  where  it  assumes  this 
character,  are  large  quarries,  in  which  the  bottom  of  it  has  not  been 
reached  at  the  depth  of  50  feet.  At  some  places  in  the  neighborhood, 
the  softer  mass  is  divided  by  thin  flags  of  hard  limestone,  and  corals 
placed  in  the  upright  position  in  which  they  grew. 

The  Red  Crag  is  distinguished  by  the  deep  ferruginous  or  ochreous 
color  of  its  sands  and  fossils,  the  Coralline  by  its  white  color.  Both  for- 
mations are  of  moderate  thickness ;  the  Red  Crag  rarely  exceeding  40, 
and  the  Coralline  seldom  amounting  to  20  feet.  But  their  importance  is 
not  to  be  estimated  by  the  density  of  the  mass  of  strata  or  its  geographical 
extent,  but  by  the  extraordinary  richness  of  its  organic  remains,  belonging 

*  See  paper  by  E.  Charlesworth,  Esq. ;  London  and  Ed.  Phil.  Mag.  No.  xxxviii. 
p.  81,  Aug.  1835. 

f  Ehrenberg  proposed  in  1831  the  term  Bryozoum,  or  "Moss-animal,"  for  the 
molluscous  or  ascidian  form  of  polyp,  characterized  by  having  two  openings  to 
the  digestive  sack,  as  in  Eschara,  Flustra,  Retepora,  and  other  zoophytes  popu- 
larly included  in  the  corals,  but  now  classed  by  naturalists  as  mollusca.  The 
term  Polyzoum,  synonymous  with  Bryozoum,  was,  it  seems,  proposed  in  1830,  or 
the  year  before,  by  Mr.  J.  V.  Thompson,  but  is  less  generally  adopted.  The  ani- 
mals of  the  Zoantharia  of  Milne  Edwards  and  Haime,  or  the  true  corals,  have 
only  one  opening  to  the  stomach. 


CH.  XIV.]  SUFFOLK  CRAG.  169 

to  a  very  peculiar  type,  which  seems  to  characterize  the  state  of  the  living 
creation  in  the  north  of  Europe  during  the  Older  Pliocene  era. 

For  a  large  collection  of  the  fish,  echinoderms,  shells,  bryozoa,  and  cor- 
als of  the  deposits  in  Suffolk,  we  are  indebted  to  the  labors  of  Mr.  Searles 
Wood.  Of  testacea  alone  he  has  obtained  230  species  from  the  Red,  and 
345  from  the  Coralline  Crag,  about  150  being  common  to  each.  The 
proportion  of  recent  species  in  the  new  group  is  considered  by  Mr.  Wood 
to  be  about  70*  per  cent.,  and  that  in  the  older  or  Coralline  about  60. 
When  I  examined  these  shells  of  Suffolk  in  1835,  with  the  assistance  of 
Dr.  Beck,  Mr.  George  Sowerby,  Mr.  Searles  Wood,  and  other  eminent 
conchologists,  I  came  to  the  opinion  that  the  extinct  species  predominated 
very  decidedly  in  number  over  the  living.  Recent  investigations,  how- 
ever, have  thrown  much  new  light  on  the  conchology  of  the  Arctic, 
Scandinavian,  British,  and  Mediterranean  Seas.  Many  of  the  species  for- 
merly known  only  as  fossils  of  the  Crag,  and  supposed  to  have  died  out, 
have  been  dredged  up  in  a  living  state  from  depths  not  previously  ex- 
plored. Other  recent  species,  before  regarded  as  distinct  from  the  nearest 
allied  Crag  fossils,  have  been  observed,  when  numerous  individuals  were 
procured,  to  be  liable  to  much  greater  variation,  both  in  size  and  form, 
than  had  been  suspected,  and  thus  have  been  identified.  Consequently, 
the  Crag  fauna  has  been  found  to  approach  much  more  nearly  to  the  re- 
cent fauna  of  the  Northern,  British,  and  Mediterranean  Seas  than  had 
been  imagined.  The  analogy  of  the  whole  group  of  testacea  to  the  Eu- 
ropean type  is  very  marked,  whether  we  refer  to  the  large  development 
of  certain  genera  in  number  of  species  or  to  their  size,  or  to  the  sup- 
pression or  feeble  representation  of  others.  The  indication  also  afforded 
by  the  entire  fauna  of  a  climate  not  much  warmer  than  that  now  pre- 
vailing in  corresponding  latitudes,  prepares  us  to  beh'eve  that  they  are  not 
of  higher  antiquity  than  the  Older  Pliocene  era. 

The  position  of  the  Red  Crag  in  Essex  to  the  subjacent  London  clay 
and  chalk  has  been  already  pointed  out  (fig.  148).  Whenever  the  two 
divisions  are  met  with  in  the  same  district,  the  Red  Crag  lies  uppermost ; 
and,  in  some  cases,  as  in  the  section  represented  in  fig.  149,  which  I  had 
an  opportunity  of  seeing  exposed  to  view  in  1839,  it  is  clear  that  the 
older  or  Coralline  mass  b  had  suffered  denudation,  before  the  newer  for- 
mation a  was  thrown  down  upon  it.  At  D  there  is  not  only  a  distinct 

Fig.  149. 
Button. 


Section  near  Ipswich,  in  Suffolk. 
a.  Bed  Crag.  6.  Coralline  Crag.  c.  London  Clay. 

cliff,  8  or  10  feet  high,  of  Coralline  Crag,  running  in  a  direction  K  E.  and 
S.  W.,  against  which  the  red  crag  abuts  with  its  horizontal  layers ;  but 

*  See  Monograph  on  the  Crag  Mollusca.    Searles  Wood,  Paleont.  Soc.  1848. 


170  OLDER  PLIOCENE   FORMATIONS.  [On.  XIY 

this  cliff  occasionally  overhangs.  The  rock  composing  it  is  drilled  every 
where  by  Pholades,  the  holes  which  they  perforated  having  been  after 
wards  filled  with  sand  and  covered  over  when  the  newer  beds  were  thrown 
down.  As  the  older  formation  is  shown  by  its  fossils  to  have  accumulated 
in  a  deeper  sea  (15,  and  sometimes  25,  fathoms  deep  or  more),  there  must 
no  doubt  have  been  an  upheaval  of  the  sea-bottom  before  the  cliff  here 
alluded  to  was  shaped  out.  We  may  also  conclude  that  so  great  an 
amount  of  denudation  could  scarcely  take  place,  in  such  incoherent  ma- 
terials, without  many  of  the  fossils  of  the  inferior  beds  becoming  mixed  up 
with  the  overlying  crag,  so  that  considerable  difficulty  must  be  occasion- 
ally experienced  by  the  palaeontologists  in  deciding  which  species  belong 
severally  to  each  group. 

The  Red  Crag  being  formed  in  a  shallower  sea,  often  resembles  in  struc- 
ture a  shifting  sand-bank,  its  layers  being  inclined  diagonally,  and  the 
planes  of  stratification  being  sometimes  directed  in  the  same  quarry  to 
the  four  cardinal  points  of  the  compass,  as  at  Butley.  That  in  this  and 
many  other  localities,  such  a  structure  is  not  deceptive  or  due  to  any  sub- 
sequent concretionary  rearrangement  of  particles,  or  to  mere  lines  of  color, 
is  proved  by  each  bed  being  made  up  of  flat  pieces  of  shell  which  lie  par- 
allel to  the  planes  of  the  smaller  strata. 

Some  fossils,  which  are  very  abundant  in  the  Red  Crag,  have  never 
been  found  in  the  white  or  coralline  division  ;  as,  for  example,  the  Fusus 
contrarius  (fig.  150),  and  several  species  of  Murex  and  Bucdnum  (or 
Nassa)  (see  figs.  151,  152),  which  two  genera  seem  wanting  in  the  lower 
crag. 

Fig.  150.  Fossils  characteristic  of  the  Red  Crag. 

Fig.  151.  Fig.  152. 


Nassa  granulata. 
Fig.  153. 


Fusm  contrarius.  Murex  atoeolatus.  Cyprceo.  coccinelloides. 

Fig.  150  half  nat.  size ;  the  others  nat  size. 

Among  the  bones  and  teeth  of  fishes  are  those  of  large  sharks  (  Carcha- 
rodon),  and  a  gigantic  skate  of  the  extinct  genus  Myliobates,  and  many 
other  forms,  some  common  to  our  seas,  and  many  foreign  to  them.  It  is 
questionable,  however,  whether  all  these  can  really  be  ascribed  to  the  era 
of  the  Red  Crag.  Not  a  few  of  them  may  possibly  have  been  derived 
from  older  strata,  especially  from  those  Upper  Eocene  formations  to  be 
described  in  the  next  chapter,  which  are  largely  developed  in  Belgium, 


CH.  XIV.]  FOSSILS  OF  THE  SUFFOLK  CEAG.  1T1 

and  of  which  a  fragment  (the  Hempstead  beds  of  Forbes)  escaped  denu- 
dation in  England. 

The  distinctness  of  the  fossils  of  the  Coralline  from  those  of  the  Red 
Crag,  arises  in  part  from  their  higher  antiquity,  and,  in  some  degree,  from 
a  difference  in  the  geographical  conditions  of  the  submarine  bottom.  The 
prolific  growth  of  corals,  echini,  and  a  prodigious  variety  of  testacea  and 
bryozoa,  implies  a  region  of  deeper  and  more  tranquil  water ;  whereas, 
the  Eed  Crag  may  have  been  formed  afterwards  on  the  same  spot,  when 
the  water  was  shallower.  In  the  mean  time  the  climate  may  have  become 
somewhat  cooler,  and  some  of  the  zoophytes  which  flourished  in  the  first 
period  may  have  disappeared,  so  that  the  fauna  of  the  Red  Crag  acquired 
a  character  somewhat  more  nearly  resembling  that  of  our  northern  seas, 
as  is  implied  by  the  large  development  of  certain  sections  of  the  genera 
Fusus,  Bucdnum,  Purpura,  and  Trochus,  proper  to  higher  latitudes,  and 
which  are  wanting  or  feebly  represented  in  the  inferior  crag. 

Some  of  the  corals  and  bryozoa  of  the  lower  Crag  of  Suffolk  belong  to 
genera  unknown  in  the  living  creation,  and  of  a  very  peculiar  structure  ; 
as,  for  example,  that  represented  in  the  annexed  fig.  (154),  which  is  one 

Fig.  154. 


Fascicularia  aurantium,  Milne  Edwards.    Family,  Tubuliporidce,  of  same  author. 
Bryozoan  of  extinct  genus,  from  the  inferior  or  Coralline  Crag,  Suffolk. 

a.  Exterior.  5.  Vertical  section  of  interior.  c.  Portion  of  exterior  magnified. 

d.  Portion  of  interior  magnified,  showing  that  it  is  made  up  of  long,  thin,  straight  tubes, 
united  in  conical  bundles. 

of  several  species  having  a  globular  form.  The^reat  number  and  variety 
of  these  zoophytes  probably  indicate  an  equable  climate,  free  from  intense 
cold  in  winter.  On  the  other  hand,  that  the  heat  was  never  excessive  is 
confirmed  by  the  prevalence  of  northern  forms  among  the  testacea,  such 
as  the  Glycinieris,  Cyprina,  and  Astarte.  Of  the  genus  last  mentioned 
(see  fig.  155)  there  are  about  fourteen  species,  many  of  them  being  rich 
in  individuals ;  and  there  is  an  absence  of  genera  peculiar  to  hot  climates, 
such  as  Conus,  Oliva,  Mitra,  Fasciolaria,  Crassatella,  and  others.  The 
cowries  (Cyprcea,  fig.  153),  also,  are  small,  and  belong  to  a  section  (Trivia) 
now  inhabiting  the  colder  regions.  A  large  volute,  called  Valuta  Lam- 
berti  (fig.  156),  may  seem  an  exception ;  but  it  differs  in  form  from  the 


172 


OLDER  PLIOCENE  FORMATIONS. 
Fig.  155. 


[Ctt  XIV. 


Astarte  (Orassina,  Lam.) ;  species  common  to  upper  and  lower  crag. 

Astarte  Omalii,  Lajonkaire;  Syn.  A.  bipartita,  Sow.  Min.  Con.  T.  521,  f.  3;  a  very  variable 
species,  most  characteristic  of  the  Coralline  Crag,  Suffolk. 

volutes  of  the  torrid  zone,  and  may,  like  the  living  Valuta  Magellanica, 
have  been  fitted  for  an  extra-tropical  climate. 


Fig.  156. 


Fig.  157. 


Fig.  158. 


Valuta,  Lambertl,  young 
Individ.,  Cor.  and  Kec 
Crag. 


Pyrula  reticulata,  Lam. ; 
Coralline     Crag,    Eam- 


Temnechinus  excavatus, 
Forbes;  Temnopleurus 
excavatus,  Wood ;  Cor. 
Crag,  Ramsholt 


The  occurrence  of  a  species  of  Lingula  at  Sutton  (see  fig.  160)  is  worthy 
of  remark,  as  these  Brachiopoda  seem  now  confined  to  more  equatorial 
latitudes ;  and  the  same  may  be  said  still  more  decidedly  of  a  species  of 
Pyrula,  supposed  by  Mr.  Wood  to  be  identical  with  P.  reticulata  (fig. 
157),  now  living  in  the  Indian  Ocean.  A  genus  also  of  echinoderms, 
called  by  Professor  Forbes  Temnechinus  (fig.  158),  is  peculiar  to  the  Red 
and  Coralline  Crag  of  Suffolk.  The  only  species  now  living  occur  in  the 
Indian  Ocean.  Whether,  therefore,  we  may  incline  to  the  belief  that  the 
mean  annual  temperature  was  higher  or  lower  than  now,  we  may  at  least 
infer  that  the  climate  an<i  geographical  conditions  were  by  no  means  the 
same  at  the  period  of  the  Suffolk  Crag  as  those  which  now  prevail  in  the 
same  region. 

One  of  the  most  interesting  conclusions  deduced  from  a  careful  com- 
parison of  the  shells  of  these  British  Older  Pliocene  strata  and  the  fauna 
of  our  present  seas,  has  been  pointed  out  by  Prof.  E.  Forbes.  It  appears 
that,  during  the  glacial  period,  a  period  intermediate,  as  we  have  seen, 
between  that  of  the  crag  and  our  own  time,  many  shells,  previously  estab- 
lished in  the  temperate  zone,  retreated  southwards  to  avoid  an  uncon- 
genial climate.  The  Professor  has  given  a  list  of  fifty  shells  which  in- 
habited the  British  seas  while  the  Coralline  and  Red  Crag  were  forming; 


Cn.  XIV.]  SUBAPENNINE  STEATA.  173 

and  which,  though  now  living  in  our  seas,  are  all  wanting  in  the  Pleisto- 
cene or  glacial  deposits.  They  must  therefore,  after  their  migration  to 
the  south,  which  took  place  during  the  glacial  period,  have  made  their 
way  northwards  again.  In  corroboration  of  these  views,  it  is  stated  that 
all  these  fifty  species  occur  fossil  in  the  Newer  Pliocene  strata  of  Sicily, 
Southern  Italy,  and  the  Grecian  Archipelago,  where  they  may  have  en- 
joyed, during  the  era  of  floating  icebergs,  a  climate  resembling  that  now 
prevailing  in  higher  European  latitudes.* 

In  the  Red  Crag  at  Felixstow,  in  Suffolk,  Professor  Henslow  has  found 
the  ear-bones  of  one  or  more  species  of  cetacea,  which,  according  to  Prof. 
Owen,  are  the  remains  of  true  whales  of  the  family  Balcenidce  (fig.  159). 
Mr.  Wood  is  of  opinion  that  these  cetacea  may  be  of  the  age  of  the  Red 
Crag,  or  if  not,  that  they  may  be  derived  from  the  destrucl'on  of  beds  of 
Coralline  Crag. 

Antwerp. — Strata  of  the  same  age  as  the  Red  and  Coralline  Crag  of 
Suffolk  have  been  long  known  in  the  country  round  Antwerp  and  on  the 
banks  of  the  Scheldt,  below  that  city.  More  than  200  species  of  testacea 

Fig.  159.  Fig.  160. 


Tympanic  bone  of  Ealasna  emarginata,  Lingula  Dumortieri,  Nyst ; 

Owen ;  Bed  Crag,  Felixstow.  Antwerp  Crag. 

have  been  collected  by  MM.  De  Wael,  Nyst,  and  others,  of  which  two- 
thirds  have  been  identified  with  Suffolk  fossils  by  Mr.  Wood.  Among 
these  he  recognizes  Lingula  Dumortieri  of  Nyst  (fig.  160),  which  I  found 
in  abundance  at  Antwerp  in  1851,  in  what  is  called  by  M.  de  Wael  the 
middle  crag.  More  than  half  of  the  shells  of  this  Antwerp  deposit  agree 
with  living  species,  and  these  belong  in  great  part  to  the  fauna  of  our 
northern  seas,  though  some  Mediterranean  species  are  not  wanting.  I 
also  met  with  numerous  cetacean  bones  of  the  genera  Balcenoptera  and 
Ziphius  in  the  same  formation.  They  are  not  at  all  rolled,  as  if  washed 
out  of  older  beds,  and  I  infer  that  the  animals  to  which  they  belonged 
once  coexisted  in  the  same  sea  with  the  associated  mollusca.f 

Normandy. — I  observed  in  1840  a  small  patch  of  shells  corresponding 
to  those  of  the  Suffolk  Crag,  near  Valognes,  in  Normandy  ;  and  there  is 
a  deposit  containing  similar  fossils  at  St.  George  Bohon,  and  several  places 
a  few  leagues  to  the  S.  of  Carentan,  in  Normandy ;  but  they  have  never 
been  traced  farther  southwards. 

Subapennine  strata. — The  Apennines,  it  is  well  known,  are  composed 
chiefly  of  secondary  rocks,  forming  a  chain  which  branches  off  from  the 
Ligurian  Alps  and  passes  down  the  middle  of  the  Italian  peninsula.  At 

*  E.  Forbes,  Mem.  GeoL  Survey,  Gt.  Brit.  vol.  i.  386. 

•j-  Lyell  on  Belgian  Tertiaries,  Quart  Journ.  Geol.  Soc.  1852,  p.  882. 


174  SUBAPENNINE  STRATA.  [Off.  XIV. 

the  foot  of  these  mountains,  on  the  side  both  of  the  Adriatic  and  the 
Mediterranean,  are  found  a  series  of  tertiary  strata,  which  form,  for  the 
most  part,  a  line  of  low  hills  occupying  the  space  between  the  older  chain 
and  the  sea.  Brocchi,  as  we  have  seen  (p.  110),  was  the  first  Italian 
geologist  who  described  this  newer  group  in  detail,  giving  it  the  name  of 
the  Subapennines ;  and  he  classed  all  the  tertiary  strata  of  Italy,  from 
Piedmont  to  Calabria,  as  parts  of  the  same  system.  Certain  mineral 
characters,  he  observed,  were  common  to  the  whole ;  for  the  strata  consist 
generally  of  light  brown  or  blue  marl,  covered  by  yellow  calcareous  sand 
and  gravel.  There  are  also,  he  added,  some  species  of  fossil  shells  which 
are  found  in  these  deposits  throughout  the  whole  of  Italy. 

We  have  now,  however,  satisfactory  evidence  that  the  Subapennine 
beds  of  Brocchi,  although  chiefly  composed  of  Older  Pliocene  strata,  be- 
long nevertheless,  in  part,  both  to  older  and  newer  members  of  the  ter- 
tiary series.  The  strata,  for  example,  of  the  Superga,  near  Turin,  are 
Miocene ;  those  of  Asti  and  Parma,  Older  Pliocene,  as  is  the  blue  marl  of 
Sienna ;  while  the  shells  of  the  incumbent  yellow  sand  of  the  same  ter- 
ritory approach  more  nearly  to  the  recent  fauna  of  the  Mediterranean,  and 
may  be  Newer  Pliocene. 

The  grayish-brown  or  blue  marl  of  the  Subapennine  formation  is  very 
aluminous,  and  usually  contains  much  calcareous  matter  and  scales  of 
mica.  Near  Parma  it  attains  a  thickness  of  2000  feet,  and  is  charged 
throughout  with  marine  shells,  some  of  which  lived  in  deep,  others  in 
shallow  water,  while  a  few  belong  to  freshwater  genera,  and  must  have 
been  washed  in  by  rivers.  Among  these  last  I  have  seen  the  common 
Limnea  palustris  in  the  blue  marl,  filled  with  small  marine  shells.  The 
wood  and  leaves,  which  occasionally  formed  beds  of  lignite  in  the  same 
deposit,  may  have  been  carried  into  the  sea  by  similar  causes.  The  shells, 
in  general,  are  soft  when  first  taken  from  the  marl,  but  they  become  hard 
when  dried.  The  superficial  enamel  is  often  well  preserved,  and  many 
shells  retain  their  pearly  lustre,  part  of  their  external  color,  and  even  the 
ligament  which  unites  the  valves.  No  shells  are  more  usually  perfect 
than  the  microscopic  foraminifera,  which  abound  near  Sienna,  where  more 
than  a  thousand  full-grown  individuals  may  be  sometimes  poured  out  of 
the  interior  of  a  single  univalve  of  moderate  dimensions. 

The  other  member  of  the  Subapennine  group,  the  yellow  sand  and  con- 
glomerate, constitutes,  in  most  places,  a  border  formation  near  the  junction 
of  the  tertiary  and  secondary  rocks.  In  some  cases,  as  near  the  town  of 
Sienna,  we  see  sand  and  calcareous  gravel  resting  immediately  on  the 
Apennine  limestone,  without  the  intervention  of  any  blue  marl.  Alterna- 
tions are  there  seen  of  beds  containing  fluviatile  shells,  with  others  filled 
exclusively  with  marine  species ;  and  I  observed  oysters  attached  to  many 
limestone  pebbles.  The  site  of  Sienna  appears  to  have  been  a  point  where 
a  river,  flowing  from  the  Apennines,  entered  the  sea  when  the  tertiary 
strata  were  formed. 

The  sand  passes  in  some  districts  into  a  calcareous  sandstone,  as  at  San 
Vignone.  Its  general  superposition  to  the  marl,  even  in  parts  of  Italy 


CH.XIV.]  MIOCENE  FOKMATIOJSTS.  175 

and  Sicily  where  the  date  of  its  origin  is  very  distinct,  may  be  explained 
if  we  consider  that  it  may  represent  the  deltas  of  rivers  and  torrents,  which 
gained  upon  the  bed  of  the  sea  where  blue  marl  had  previously  been  de- 
posited. The  latter,  being  composed  of  the  finer  and  more  transportable 
mud,  would  be  conveyed  to  a  distance,  and  first  occupy  the  bottom,  over 
which  sand  and  pebbles  would  afterwards  be  spread,  in  proportion  as 
rivers  pushed  their  deltas  farther  outwards.  In  some  large  tracts  of  yel- 
low sand  it  is  impossible  to  detect  a  single  fossil,  while  in  other  places 
they  occur  in  profusion.  Occasionally  the  shells  are  silicified,  as  at  San 
Vitale,  near  Parma,  from  whence  I  saw  two  individuals  of  recent  species, 
one  freshwater  and  the  other  marine  (Lymnea  palustris,  and  Cytherea 
concentrica,  Lam.),  both  perfectly  converted  into  flint. 

Rome. — The  seven  hills  of  Home  are  composed  \  artly  of  marine  ter- 
tiary strata,  those  of  Monte  Mario,  for  example,  of  the  Older  Pliocene 
period,  and  partly  of  superimposed  volcanic  tuff,  on  the  top  of  which  are 
usually  cappings  of  a  fluviatile  and  lacustrine  deposit.  Thus,  on  Mount 
Aventine,  the  Vatican,  and  the  Capitol,  we  find  beds  of  calcareous  tufa 
with  incrusted  reeds,  and  recent  terrestrial  shells,  at  the  height  of  about 
200  feet  above  the  alluvial  plain  of  the  Tiber.  The  tusk  of  the  mammoth 
has  been  procured  from  this  formation,  but  the  shells  appear  to  be  all  of 
living  species,  and  must  have  been  imbedded  when  the  summit  of  the 
Capitol  was  a  marsh,  and  constituted  one  of  the  lowest  hollows  of  the 
country  as  it  then  existed.  It  is  not  without  interest  that  we  thus  dis- 
cover the  extremely  recent  date  of  a  geological  event  which  preceded  an 
historical  era  so  remote  as  the  building  of  Rome. 

Aralo- Caspian  formations. — This  name  has  been  given  by  Sir  R.  Mur- 
chison  and  M.  de  Verneuil  to  the  limestone  and  associated  sandy  beds,  of 
brackish-water  origin,  which  have  been  traced  over  a  very  extensive  area 
surrounding  the  Caspian,  Azoff,  and  Aral  Seas,  and  parts  of  the  northern 
and  western  coasts  of  the  Black  Sea.  The  fossil  shells  are  partly  fresh- 
water, as  Paludina,  Neritina,  <fec.,  and  partly  marine,  of  the  family  Car- 
dizcice  and  Mytili.  The  species  are  identical,  in  great  part,  with  those 
now  inhabiting  the  Caspian  ;  and  when  not  living,  they  are  analogous  to 
forms  now  found  in  the  inland  seas  of  Asia,  rather  than  to  oceanic  types. 
The  limestone  rises  occasionally  to  the  height  of  several  hundred  feet  above 
the  sea,  and  is  supposed  to  indicate  the  former  existence  of  a  vast  inland 
sheet  of  brackish  water  as  large  as  the  Mediterranean,  or  larger. 

The  proportion  of  recent  species  agreeing  with  the  fauna  of  the  Caspian 
is  so  considerable  as  to  leave  no  doubt  in  the  minds  of  the  geologists  above 
cited,  that  this  rock,  also  called  by  them  the  "  Steppe  Limestone,"  belongs 
to  the  Pliocene  period.* 

MIOCENE  FORMATIONS. 

Faluns  of  Touraine. — The  strata  which  we  meet  with  next  in  the  de- 
scending order  are  those  called  by  many  geologists  "  Middle  Tertiary," 

*  Geol.  of  Russia,  p.  279,  <fcc. 


176  FALUNS  OF  TOURAINE.  [Cn.  XIV. 

and  for  which  in  1833  I  proposed  the  name  of  Miocene,  selecting  the 
faluns  of  the  valley  of  the  Loire  in  France  as  my  example  or  type. 
No  strata  contemporaneous  with  these  formations  have  as  yet  been  met 
with  in  the  British.  Isles,  where  the  lower  crag  of  Suffolk  is  the  deposit 
nearest  in  age.  The  term  "faluns"  is  given  provincially  by  French 
agriculturists  to  shelly  sand  and  marl  spread  over  the  land  in  Touraine, 
just  as  the  "  crag"  was  formerly  much  used  to  fertilize  the  soil  in  Suffolk. 
Isolated  masses  of  such  faluns  occur  from  near  the  mouth  of  the  Loire,  in 
the  neighborhood  of  Nantes,  to  as  far  inland  as  a  district  south  of  Tours. 
They  are  also  found  at  Pontlevoy,  on  the  Cher,  about  70  miles  above  the 
junction  of  that  river  with  the  Loire,  and  30  miles  S.  E.  of  Tours.  De- 
posits of  the  same  age  also  appear  under  new  mineral  conditions  near  the 
towns  of  Dinan  and  Rennes,  in  Brittany.  I  have  visited  all  the  locali- 
ties above  enumerated,  and  found  the  beds  on  the  Loire  to  consist  princi- 
pally of  sand  and  marl,  in  which  are  shells  and  corals,  some  entire,  some 
rolled,  and  others  in  minute  fragments.  In  certain  districts,  as  at  Doue, 
in  the  department  of  Maine  and  Loire,  10  miles  S.  W.  of  Saumur,  they 
form  a  soft  building-stone,  chiefly  composed  of  an  aggregate  of  broken 
shells,  bryozoa,  corals,  and  echinoderms,  united  by  a  calcareous  cement ; 
the  whole  mass  being  very  like  the  Coralline  Crag  near  Aldborough  and 
Sudbourn  in  Suffolk.  The  scattered  patches  of  faluns  are  of  slight 
thickness,  rarely  exceeding  50  feet ;  and  between  the  district  called 
Sologne  and  the  sea  they  repose  on  a  great  variety  of  older  rocks ;  being 
seen  to  rest  successively  upon  gneiss,  clayslate,  various  secondary  for- 
mations, including  the  chalk ;  and,  lastly,  upon  the  upper  freshwater 
limestone  of  the  Parisian  tertiary  series,  which,  as  before  mentioned 
(p.  Ill),  stretches  continuously  from  the  basin  of  the  Seine  to  that  of 
the  Loire. 

At  some  points,  as  at  Louans,  south  of  Tours,  the  shells  are  stained  of 
a  ferruginous  color,  not  unlike  that  of  the  Red  Crag  of  Suffolk.  The 
species  are,  for  the  most  part,  marine,  but  Fig.  iei. 

a  few  of  them  belong  to  land  and  fluviatile 
genera,  Among  the  former,  Helix  turo- 
nensis  (fig.  45,  p.  30)  is  the  most  abun- 
dant. Remains  of  terrestrial  quadrupeds 
are  here  and  there  intermixed,  belonging 
to  the  genera  Deinotherium  (fig.  161), 
Mastodon,  Rhinoceros,  Hippopotamus, 
Chseropotamus,  Dichobune,  Deer,  and 
others,  and  these  are  accompanied  by 
cetacea,  such  as  the  Lamantine,  Morse, 
Sea-Calf,  and  Dolphin,  all  of  extinct 

species.  Deinotherium  giganteum,  Kaup. 

Professor  E.- Forbes,  after  studying  the  fossil  testacea  which  I  obtained 
from  these  beds,  informs  me  that  he  has  no  doubt  they  were  formed 
partly  on  the  shore  itself  at  the  level  of  low  water,  and  partly  at  very 
moderate  depths,  not  exceeding  ten  fathoms  below  that  level.  The  mol- 


CH.  XIV.]       COMPARISON  OF   THE   CRAG  AJSTD   FALUNS.  177 

luscous  fauna  of  the  "  faluns"  is  on  the  whole  much  more  littoral  than 
that  of  the  Bed  and  Coralline  Crag  of  Suffolk,  and  implies  a  shallower 
sea.  It  is,  moreover,  contrasted  with  the  Suffolk  Crag  by  the  indications 
it  affords  of  an  extra-European  climate.  Thus  it  contains  seven  species  of 
Cyprcea,  some  larger  than  any  existing  cowry  of  the  Mediterranean,  sev- 
eral species  of  Oliva,  Ancillaria,  Mitra,  Terebra,  Pyrula,  Fasciolaria, 
and  Conus.  Of  the  cones  there  are  no  less  than  eight  species,  some  very 
large,  whereas  the  only  European  cone  is  of  diminutive  size.  The  genus 
Nerita,  and  many  others,  are  also  represented  by  individuals  of  a  type  now 
characteristic  of  equatorial  seas,  and  wholly  unlike  any  Mediterranean 
forms.  These  proofs  of  a  more  elevated  temperature  seem  to  imply  the 
higher  antiquity  of  the  faluns  as  compared  with  the  Suffolk  Crag,  and 
are  in  perfect  accordance  with  the  fact  of  the  smaller  proportion  of  testacea 
of  recent  species  found  in  the  faluns. 

Out  of  290  species  of  shells,  collected  by  myself  in  1840  at  Pontlevoy, 
Louans,  Bossee,  and  other  villages  twenty  miles  south  of  Tours ;  and  at 
Savigne,  about  fifteen  miles  northwest  of  that  place,  seventy-two  only 
could  be  identified  with  recent  species,  which  is  in  the  proportion  of 
twenty-five  per  cent.  A  large  number  of  the  290  species  are  common  to 
all  the  localities,  those  peculiar  to  each  not  being  more  numerous  than  we 
might  expect  to  find  in  different  bays  of  the  same  sea. 

The  total  number  of  testaceous  mollusca  from  the  faluns,  in  my  pos- 
session, is  302  ;  of  which  forty-five  only  were  found  by  Mr.  Wood  to  be 
common  to  the  Suffolk  Crag.  The  number  of  corals,  including  bryozoa 
and  zoantharia,  obtained  by  me  at  Doue,  and  other  localities  before  ad- 
verted to,  amounts  to  forty-three,  as  determined  by  Mr.  Lonsdale,  of  which 
seven  (one  of  them  a  zoantharian)  agree  specifically  with  those  of  the  Suf- 
folk Crag.  Only  one  has,  as  yet,  been  identified  with  a  living  species. 
But  it  is  difficult,  notwithstanding  the  advances  recently  made  by  MM. 
Dana,  Milne  Edwards,  Haime,  and  Lonsdale,  to  institute  a  satisfactory 
comparison  between  recent  and  fossil  zoantharia  and  bryozoa.  Some  of  the 
genera  occurring  fossil  in  Touraine,  as  the  Astrea,  Dendrophyllia,  Lunu- 
lites,  have  not  been  found  in  European  seas  north  of  the  Mediterranean  ; 
nevertheless  the  zoantharia  of  the  faluns  do  not  seem  to  indicate  on  the 
whole  so  warm  a  climate  as  would  be  inferred  from  the  shells. 

It  was  stated  that,  on  comparing  about  300  species  of  Touraine  shells 
with  about  450  from  the  Suffolk  Crag,  forty-five  only  were  found  to  be 
common  to  both,  which  is  in  the  proportion  of  only  fifteen  per  cent. 
The  same  small  amount  of  agreement  is  found  in  the  corals  also.  I  for- 
merly endeavored  to  reconcile  this  marked  difference  in  species  with  the 
supposed  coexistence  of  the  two  faunas,  by  imagining  them  to  have  sever- 
ally belonged  to  distinct  zoological  provinces  or  two  seas,  the  one  opening 
to  the  north,  and  the  other  to  the  south,  with  a  barrier  of  land  between 
them,  like  the  Isthmus  of  Suez,  separating  the  Eed  Sea  and  the  Medi- 
terranean. But  I  now  abandon  that  idea  for  several  reasons ;  among 
others,  because  I  succeeded  in  1841  in  tracing  the  Crag  fauna  southwards 
in  Normandy  to  within  seventy  miles  of  the  Falunian  type,  near  Dinan, 

12 


178  SHELLS  IN  MIOCENE  STRATA.  [On. 

yet  found  that  both  assemblages  of  fossils  retained  their  distinctive  char 
acters,  showing  no  signs  of  any  blending  of  species  or  transition  of  cli- 
mate. 

On  a  comparison  of  280  Mediterranean  shells  with  600  British  species, 
made  for  me  by  an  experienced  conchologist  in  1841,  160  were  found  to 
be  common  to  both  collections,  which  is  in  the  proportion  of  fifty-seven 
per  cent.,  a  fourfold  greater  specific  resemblance  than  between  the  seas  of 
the  crag  and  the  faluns,  notwithstanding  the  greater  geographical  dis- 
tance between  England  and  the  Mediterranean  than  between  Suffolk  and 
the  Loire.  The  principal  grounds,  however,  for  referring  the  English  crag 
to  the  Older  Pliocene  and  the  French  faluns  to  the  Miocene  epochs,  con- 
sist in  the  predominance  of  fossil  shells  in  the  British  strata  identifiable 
with  species,  not  only  still  living,  but  which  are  now  inhabitants  of  neigh- 
boring seas,  while  the  accompanying  extinct  species  are  of  genera  such 
as  characterize  Europe.  In  the  faluns,  on  the  contrary,  the  recent  species 
are  in  a  decided  minority  ;  and  most  of  them  ar.e  now  inhabitants  of  the 
Mediterranean,  the  coast  of  Africa,  and  the  Indian  Ocean ;  in  a  word, 
less  northern  in  character  and  pointing  to  the  prevalence  of  a  warmer 
climate.  They  indicate  a  state  of  things  receding  farther  from  the  present 
condition  of  central  Europe  in  physical  geography  and  climate,  and 
doubtless  therefore  receding  farther  from  our  era  in  time. 

Bourdeaux. — A  great  extent  of  country  between  the  Pyrenees  and  the 
Gironde  is  overspread  by  tertiary  deposits  of  various  ages  from  the  Eocene 
to  the  Pliocene.  Among  these,  especially  near  Saucats  in  the  environs 
of  Bourdeaux,  and  at  Merignac  and  Bazas  in  the  same  region,  are 
sands  containing  marine  shells,  and  corals  of  the  type  of  the  Touraine 
faluns.* 

Belgium. — In  a  small  hill  or  ridge  called  the  Bolderberg,  which  I 
visited  in  1851,  situated  near  Hasselt,  about  forty  miles  E.  N.  E.  of  Brus- 
sels, strata  of  sand  and  gravel  occur,  to  which  M.  Dumont  first  called 
attention  as  appearing  to  constitute  a  northern  representative  of  the  faluns 
of  Touraine.  They  are  quite  distinct  in  their  fossils  from  the  Antwerp 
Crag  before  mentioned,  and  contain  shells  of  the  genera  Oliva,  Conus, 
Ancillaria,  Pleurotoma,  and  Cancellaria  in  abun- 
dance. The  most  common  shell  is  an  Olive  (see 
fig.  162),  called  by  Nyst  Oliva  Dufresnii,  Bast; 
but  which  is  undoubtedly,  as  M.  Bosquet  observes, 
smaller  and  shorter  than  the  Bourdeaux  species. f 

North  Germany. — We  learn  from  the  able  trea- 
tise published  by  M.  Beyrich,  in  1853,  that  the 
fossil  fauna  above  alluded  to,  which  is  so  meagerly 
exhibited  in  the  Bolderberg,  is  rich  in  species  in  a> fro^  view ;  &,  back  view. 
other  localities  in  North  Germany,  as  in  Mecklenburg,  Liineburg,  the 

*  See  a  Memoir  by  V.  Raulin,  1848  :  Bourdeaux. 

f  Lyell  on  Belgian  Tertiaries,  Quart.  Geol.  Journ.  1852,  p.  295.     Nyst's  figure 
seems  to  be  copied  from  that  given  by  Basterot  of  the  Bourdeaux  fossil. 
J  Die  Conchylien  des  Norddeutschen  Tertiargebirge  :  Berlin,  1853. 


CH.  XIV.]  SHELLS  IN  MIOCENE  STRATA.  179 

Island  Sylt,  and  at  Bersenbrtick  north  of  Osnabriick,  in  Westphalia, 
where  it  was  first  discovered  by  F.  Komer.  It  is  also  said  to  occur  at 
Bocholt,  and  other  points  in  Westphalia ;  on  the  borders  of  Holland ; 
also  at  Crefeld  and  Dusseldorf.  Not  having  visited  these  localities,  I  can 
offer  no  opinion  as  to  the  agreement  in  age  of  the  several  deposits  here 
enumerated. 

Vienna  basin. — In  South  Germany  the  general  resemblance  of  the 
shells  of  the  Vienna  tertiary  basin  with  those  of  the  faluns  of  Touraine 
has  long  been  acknowledged.  In  Dr.  Homes'  excellent  work,  recently 
commenced,  on  the  fossil  mollusca  of'  that  formation,  we  see  figures  of 
many  shells  of  the  genus  Conus,  some  of  large  size,  clearly  of  the  same 
species  as  those  found  in  the  falunian  sands  of  Touraine.  M.  Alcide 
d'Orbigny  has  also  shown  that  the  foraminifera  of  the  Vienna  basin  differ 
alike  from  the  Eocene  and  Pliocene  species,  and  agree  with  those  of  the 
faluns,  so  far  as  the  latter  are  known.  Among  the  Vienna  foraminifera, 
the  genus  Amphistegina  (fig.  163)  is  very  characteristic,  and  is  supposed 

Fig.  163. 


Ampkistegina  ffatierina,  D'Orb.    Vienna,  miocene  strata. 

by  Archiac  to  take  the  same  place  among  the  foraminifera  of  the  Miocene 
era,  which  the  Nummulites  occupy  in  the  Eocene  period. 

The  Vienna  basin  is  thought  by  some  geologists  to  comprise  tertiary 
strata  of  more  than  one  age,  the  lowest  strata  reached  in  boring  Artesian 
wells  being  older  than  the  faluns. 

Piedmont. — Switzerland. — To  the  same  Miocene  or  "  falunian"  epoch, 
we  may  refer  a  portion  of  the  strata  of  the  Hill  of  the  Superga  near 
Turin  in  Piedmont,*  as  also  part  of  the  Molasse  of  Switzerland,  or  the 
greenish  sand  which  fills  the  great  Swiss  valley  between  the  Alps  and  the 
Jura.  At  the  foot  of  the  Alps  it  usually  takes  the  form  of  a  conglomerate 
called  provincially  "  nagelflue,"  sometimes  attaining  the  truly  wonderful 
thickness  of  6000  and  8000  feet,  as  in  the  Riga  near  Lucerne  and  in 
the  Speer  near  Wesen.  The  lower  portion  of  this  molasse  is  of  freshwater 
origin. 

Scotland. — Isle  of  Mull. — In  the  sea-cliffs  forming  the  headland  of 
Ardtun  on  the  west  coast  of  Mull,  in  the  Hebrides,  several  bands  of  ter- 
tiary strata  containing  leaves  of  dicotyledonous  plants  were  discovered  *in 
1851  by  the  Duke  of  Argyle.f  From  his  description  it  appears  that 
there  are  three  leaf-beds,  varying  in  thickness  from  1 J  to  2j  feet,  which 
are  interstratified  with  volcanic  tuff  and  trap,  the  whole  mass  being  about 
130  feet  in  thickness.  A  sheet  of  basalt  40  feet  thick  covers  the  whole  ; 

*  See  Sig.  Giov.  Micnelotti's  works.  \   Quart  GeoL  Journ.  1851,  p.  89. 


180  PLIOCENE  AND   MIOCENE  FORMATIONS-        [On.  XIV 

and  another  columnar  bed  of  the  same  rock  10  feet  thick  is  exposed  at 
the  bottom  of  the  cliff.  One  of  the  leaf-beds  consists  of  a  compressed 
mass  of  leaves  unaccompanied  by  any  stems,  as  if  they  had  been  blown 
into  a  marsh  where  a  species  of  Equisetum  grew,  of  which  the  remains 
are  plentifully  imbedded  in  clay. 

It  is  supposed  by  the  Duke  of  Argyle  that  this  formation  was  accumu- 
lated in  a  shallow  lake  or  marsh  in  the  neighborhood  of  a  volcano,  which 
emitted  showers  of  ashes  and  streams  of  lava.  The  tufaceous  envelope  of 
the  fossils  may  have  fallen  into  the  lake  from  the  air  as  volcanic  dust, 
or  have  been  washed  down  into  it  as  mud  from  the  adjoining  land.  The 
deposit  is  decidedly  newer  than  the  chalk,  for  chalk  flints  containing  cre- 
taceous fossils  were  detected  by  the  Duke  in  the  principal  mass  of  vol- 
canic ashes  or  tuff.* 

The  leaves  belong  to  species,  and  sometimes  even  to  families,  no  longer 
indigenous  in  the  British  Isles  ;  and  "  their  climatal  aspect,"  says  Pro- 
fessor E.  Forbes,  "  is  more  mid-European  than  that  of  the  English  Eocene 
Flora.  They  also  resemble  some  of  the  Miocene  plants  of  Croatia  de- 
scribed by  Unger."  Some  of  them  appear  to  belong  to  a  coniferous  tree, 
possibly  a  yew  (Taxus)  ;  others,  still  more  abundant,  to  a  plane  (Platanus), 
having  the  same  outline  and  veining  well  preserved.  No  accompanying 
fossil  shells  have  been  met  with,  and  there  seems  therefore  the  same  un- 
certainty in  determining  whether  these  beds  are  Upper  Eocene  or  Mio- 
cene, which  we  experience  when  we  endeavor  to  fix  the  age  of  many  con- 
tinental Brown-Coal  formations,  those  of  Croatia  not  excepted. 

These  interesting  discoveries  in  Mull  naturally  raise  the  question, 
whether  the  basalt  of  Antrim  in  Ireland,  and  of  the  celebrated  Giant's 
Causeway,  may  not  be  of  the  same  age.  For  in  Antrim  the  basalt  over- 
lies the  chalk,  and  the  upper  mass  of  it  covers  everywhere  a  bed  of  lignite 
and  charcoal,  in  which  wood,  with  the  fibre  well  preserved,  and  evidently 
dicotyledonous,  is  preserved.f  The  general  dearth  of  strata  in  the  British 
Isles,  intermediate  in  age  between  the  formation  of  the  Eocene  and  Plio- 
cene periods,  may  arise,  says  Professor  Forbes,  from  the  extent  of  dry  land 
which  prevailed  in  the  last  interval  of  time  alluded  to.  If  land  predomi- 
nated, the  only  monuments  we  are  likly  ever  to  find  of  Miocene  date  are 
those  of  lacustrine  and  volcanic  origin,  such  as  these  Ardtun  beds  in 
Mull,  or  the  lignites  and  associated  basalts  in  Antrim.  On  the  flanks  of 
Mont  Dor,  in  Auvergne,  I  have  seen  leaf-beds  among  the  ancient  volcanic 
tuffs  which  I  have  always  supposed  to  be  of  Miocene  date.  Some  of  the 
Brown-Coal  deposits  of  Germany  are  believed  to  be  Miocene  ;  others,  as 
will  be  seen  in  the  next  chapter,  are  Eocene,  Upper  or  Middle. 

Older  Pliocene  and  Miocene  formations  in  the  United  States. — Be- 
tween the  Alleghany  mountains,  formed  of  older  rocks,  and  the  Atlantic, 
there  intervenes,  in  the  United  States,  a  low  region  occupied  principally 
by  beds  of  marl,  clay,  and  sand,  consisting  of  the  cretaceous  and  tertiary 
formations,  and  chiefly  of  the  latter.  The  general  elevation  of  this  plain 

*  Quart.  Geol.  Journ.  185T,  p.  90.  f  Duke  of  Argyle,  ibid.  p.  101. 


CH.  XIV.]  IX   UNITED   STATES,   AND   IN   INDIA.  181 

bordering  the  Atlantic  does  not  exceed  100  feet,  although  it  is  sometimes 
several  hundred  feet  high.  It*  width  in  the  middle  and  southern  states 
is  very  commonly  from  100  to  150  miles.  It  consists,  in  the  south,  as  in 
Georgia,  Alabama,  and  South  Carolina,  almost  exclusively  of  Eocene  de- 
posits ;  but  in  North  Carolina,  Maryland,  Virginia,  Delaware,  more 
modern  strata  predominate,  which,  after  examining  them  in  1842,  1  sup- 
posed to  be  of  the  age  of  the  English  crag  and  Faluns  of  Touraine.*  If, 
chronologically  speaking,  they  can  be  truly  said  to  be  the  representatives 
of  these  two  European  formations,  they  may  range  in  age  from  the  Older 
Pliocene  to  the  Miocene  epoch,  according  to  the  classification  of  European 
strata  adopted  in  this  chapter. 

The  proportion  of  fossil  shells  agreeing  with  recent,  out  of  147  species 
collected  by  me,  amounted  to  about  17  per  cent.,  or  one-sixth  of  the 
whole  ;  but  as  the  fossils  so  assimilated  were  almost  always  the  same  as 
species  now  living  in  the  neighboring  Atlantic,  the  number  may  hereafter 
be  augmented,  when  the  recent  fauna  of  that  ocean  is  better  ktiown. 
In  different  localities,  also,  the  proportion  of  recent  species  varied  con- 
siderably. 

On  the  banks  of  the  James  River,  in  Virginia,  about  20  miles  below 
Richmond,  in  a  cliff  about  30  feet  high,  I  observed  yellow  and  white 
sands  overlying  an  Eocene  marl,  just  as  the  yellow  sands  of  the  crag  lie 
on  the  blue  London  clay  in  Suffolk  and  Essex  in  England.  In  the  Vir- 
ginian sands,  we  find  a  profusion  of  an  Astarte  (A.  undulata,  Conrad), 
which  resembles  closely,  and  may  possibly  be  a  variety  of,  one  of  the 
commonest  fossils  of  the  Suffolk  Crag  (A.  bipartita)  ;  the  other  shells 
also,  of  the  genera  Natka,  Fissurella,  Artemis,  Lucina,  Chama,  Pectun- 
culus,  and  Pecten,  are  analogous  to  shells  both  of  the  English  crag  and 
French  faluns,  although  the  species  are  almost  all  distinct.  Out  of  147 
of  these  American  fossils  I  could  only  find  13  species  common  to  Europe, 
and  these  occur  partly  in  the  Suffolk  Crag,  and  partly  in  the  faluns  of 


Fig.  165. 


Fulgur  canaliculatus.    Maryland.  Fusus  quadricoslatus,  Say.    Maryland. 

Touraine ;  but  it  is  an  important  characteristic  of  the  American  group, 
that  it  not  only  contains  many  peculiar  extinct  forms,  such  as  Fusus 

*  Proceed,  of  the  Geol.  Soc.  vol.  iv.  part  3,  1845,  p.  547. 


182  PLIOCENE  AND  MIOCENE  FORMATIONS,   ETC.     [Cii.  XIV 

quadricostatus,  Say  (see  fig.  165),  and  Venus  tridacnoides,  abundant  in 
these  same  formations,  but  also  some  shells  which,  like  Fulgur  carica  01 
Say  and  F.  canaliculatus  (see  fig.  164),  Calyptrcea  costata,  Venus  merce- 
naria,  Lam.,  Modiola  glandula,  Totten,  and  Pecten  magellanicus^  Lam., 
are  recent  species,  yet  of  forms  now  confined  to  the  western  side  of  the 
Atlantic, — a  fact  implying  that  some  traces  of  the  beginning  of  the  pres- 
ent geographical  distribution  of  mollusca  date  back  to  a  period  as  remote 
as  that  of  the  Miocene  strata. 

Of  ten  species  of  zoophytes  which  I  procured  on  the  banks  of  the 
James  River,  one  was  formerly  supposed  by  Mr.  Lonsdale  to  be  identical 
with  a  fossil  from  the  faluns  of  Touraine,  but  this  species  (see  fig.  166) 
proves  on  re-examination  to  be  different,  and  to 
agree  generically  with  a  coral  now  living  on 
the  coast  of  the  United  States.  With  respect 
to  climate,  Mr.  Lonsdale  regards  these  corals  as 
indicating  a  temperature  exceeding  that  of  the 
Mediterranean,  and  the  shells  would  lead  to  sim- 
ilar conclusions.  Those  occurring  on  the  James 
River  are  in  the  37th  degree  of  N.  latitude, 
while  the  French  faluns  are  in  the  47th :  yet 

,       „  <«•!*          •          />M  IT  i        Astrangia  linecita,  Lonsdale. 

the  lorms  or  the  American  lossils  would  scarcely    gyn.  Anthophyiium  Uneatum. 
imply  so  warm  a  climate  as  must  have  prevailed       Williams^r'sh.  Virginia. 
in  France  when  the  Miocene  strata  of  Touraine  originated. 

Among  the  remains  of  fish  in  these  Post-Eocene  strata  of  the  United 
States  are  several  large  teeth  of  the  shark  family,  not  distinguishable 
specifically  from  fossils  of  the  faluns  of  Touraine. 

India. — Sewalik  Hills. — The  freshwater  deposits  of  the  sub-Hima- 
layan or  Sewalik  Hills,  described  by  Dr.  Falconer  and  Captain  Cautley, 
belong  probably  to  some  part  of  the  Miocene  period,  although  it  is  diffi- 
cult to  decide  this  question  until  the  accompanying  freshwater  and  land- 
shells  have  been  more  carefully  determined  and  compared  with  fossils  of 
other  tertiary  deposits.  The  strata  are  certainly  newer  than  the  num. 
mulitic  rocks  of  India,  and,  like  the  faluns  of  Touraine,  they  contain  the 
genera  Deinotheri:im  and  Mastodon,  with  which  are  associated  no  less 
than  seven  extinct  species  of  elephants.  The  presence  of  a  fossil  giraffe 
and  hippopotamus,  genera  now  only  living  in  Africa,  and  of  a  camel,  an 
inhabitant  of  extensive  plains,  implies  a  former  geographical  state  of 
things  strongly  contrasted  with  what  now  prevails  in  the  same  region. 
A  species  of  Anoplotherium  (A.  posterogenium)  forms  a  link  between 
this  fauna  and  that  of  the  Eocene  period  ;  yet,  on  the  whole,  the  Sewalik 
mammalia  have  a  more  modern  aspect  than  those  of  the  Upper  Eocene, 
so  many  being  referable  to  existing  genera,  whereas  almost  every  Eocene 
genus  is  extinct.  Moreover,  the  sub-Himalayan  fauna  exhibits  a  great 
development  of  the  Ruminants,  an  order  so  feebly  represented  in  the 
Eocene  period.  In  addition  to  the  camel  and  giraffe  already  alluded  to, 
we  have  here  the  huge  Sivatherium,  a  ruminant  bigger  than  the  rhi- 
noceros, and  provided  with  a  large  upper  lip,  if  not  a  short  proboscis,  and 


CH.  XV.]         UPPER  EOCEXE  FORMATIONS.  183 

having  two  pair  of  horns  resembling  those  of  antelopes.  The  number  of 
species  of  the  genus  Antelope  is  also  remarkable.  In  the  same  fauna 
appear  many  carnivorous  beasts,  often  belonging  to  existing  genera,  and 
several  species  of  monkey.  Among  the  reptiles  are  crocodiles,  some 
larger  than  any  now  living ;  and  an  enormous  tortoise,  Testudo  Atlas,  the 
curved  shell  of  which  measured  twenty  feet  across. 


CHAPTER  XV. 

UPPER   EOCENE    FORMATIONS. 

(Lower  Miocene  of  many  authors) 

Preliminary  remarks  on  classification,  and  on  the  line  of  separation  between 
Eocene  and  Miocene  strata — Whether  the  Limburg  and  contemporaneous  for- 
mations should  be  called  Upper  Eocene — Limburg  strata  in  Belgium — Strata 
of  same  age  in  North  Germany — Mayence  basin — Brown  Coal  of  Germany — 
Upper  Eocene  of  Hempstead  Hill,  Isle  of  Wight — Upper  Eocene  of  France — 
Lacustrine  strata  of  Auvergne — Indusial  limestone — Freshwater  strata  of  the 
Cantal — Its  resemblance  in  some  places  to  white  chalk  with  flints — Proofs  of 
gradual  deposition — Upper  Eocene  of  Bourdeaux,  Aix-en-Provence,  Malta,  <kc. 
— Upper  Eocene  of  Nebraska,  United  States. 

Preliminary  remarks. — In  the  last  chapter  it  was  stated  that  as  yet  we 
know  of  no  marine  strata  in  the  British  Isles  contemporaneous  with  the 
faluns  of  Touraine,  or  those  shelly  deposits  of  the  valley  of  the  Loire 
which  I  selected  as  the  type  of  the  Miocene  period.  There  have,  how- 
ever, been  recently  discovered  in  the  Isle  of  Wight  certain  fluvio-marine 
deposits,  which  many  continental  geologists  would  call  "  Lower  Miocene," 
the  "  faluns"  being  termed  by  them  "  Upper  Miocene."  A  few  prelimi- 
nary remarks  on  this  difference  of  nomenclature,  bearing  as  it  does  on 
questions  involving  the  first  principles  of  classification,  will  be  necessarj 
before  I  treat  of  the  Upper  Eocene  formations. 

The  marine  strata,  which  in  the  north  of  France  come  next  in  chrono- 
logical order  to  the  "  faluns,"  or  which  immediately  precede  them  in  age, 
are  the  sands  and  sandstones,  called  the  "  Ores  de  Fontainebleau,"  01 
"sables  marins  superieurs."  (See  General  Table,  p.  104.)  They  consti- 
tute the  uppermost  beds  of  the  Paris  basin,  and  are  overlaid  by  a  fresh- 
water limestone  called  "  Calcaire  de  la  Beauce."  The  upper  marine  sands 
•ontain  no  fossil  shells  common  to  the  faluns,  or  extremely  few  species ; 
and  no  shells  of  living  species,  or,  if  so,  they  are  about  as  scarce  as  in  the 
Middle  or  typical  Eocene  groups.  In  consequence  of  this  distinctness  in 
the  fossils,  and  for  other  reasons  presently  to  be  mentioned,  I  excluded 
these  "  upper  sands"  from  the  Miocene  period  in  former  editions  of  this 
work,  availing  myself  of  the  hiatus  between  the  Ores  de  Fontainebleau 
and  the  faluns  to  draw  a  line  of  separation  between  Eocene  and  Miocene. 


184:  KEMARKS  ON  CLASSIFICATION.  [Cn.  XV 

In  support  of  this  classification  I  pointed  out  the  fact  that  the  "  uppei 
marine  sands,"  or  Gres  de  Fontainebleau  of  the  Parisian  series,  with  their 
characteristic  shells,  extend  southwards  from  the  French  metropolis,  as 
far  as  Etampes,  which  is  within  seventy  miles  of  Pontlevoy,  near  Blois, 
rtiid  not  more  than  100  miles  from  Savigne,  near  Tours,  two  localities 
where  fhefalunian  shells  are  very  abundant.  So  remarkable  a  difference 
between  the  species  of  the  valley  of  the  Loire  and  those  of  the  valley 
of  the  Seine  cannot  be  the  result  of  geographical  distribution  at  one 
and  the  same  former  era,  but  must  evidently  have  depended  on  a  differ- 
ence in  the  age  of  the  deposits.  It  marks  the  influence  of  Time,  and 
not  of  Space. 

Another  reason  which  induced  me  to  class  the  Gres  de  Fontainebleau 
and  strata  of  the  same  age  with  the  older  series  rather  than  with  the 
newer,  was  the  decidedly  Eocene  aspect  of  the  testaceous  fauna,  and  the 
fact  that  a  certain  proportion  of  the  shells  of  the  "  upper  sands"  are  of 
species  common  to  the  underlying  Parisian  strata. 

A  different  arrangement,  however,  was  adopted  by  MM.  Dufrenoy  and 
E.  de  Beaumont,  in  their  coloring  of  the  Government  Map  of  France,  for 
they  comprehended  in  their  Miocene  group,  not  only  the  faluns  of  Tou- 
raine,  but  also  the  freshwater  "  calcaire  de  la  Beauce,"  and  the  marine 
sands  and  sandstone  (Gres  de  Fontainebleau),  i.  e.  all  the  tertiary  de- 
posits which  lie  above  the  gypseous  series  of  Montmartre,  a  formation 
well  known  as  rich  in  extinct  mammalia,  first  brought  to  light  by  the 
genius  of  Cuvier.  M.  D'Archiac,  in  1839,  followed  the  same  mode  of 
classification,  dividing  what  he  termed  "  Lower"  from  his  "  Middle  ter- 
tiary" in  the  same  way.  M.  Deshayes,  in  his  work  on  the  Fossil  Shells 
of  the  Environs  of  Paris  (1824-1837),  had  given  twenty-nine  species 
as  belonging  to  the  upper  marine  strata,  nearly  all  of  which  he  distin- 
guished specifically  from  shells  of  the  Calcaire  Grossier,  although  he 
regarded  them  as  characteristic  of  the  same  fauna.  The  railway  cut- 
tings near  Etampes,  in  1849,  enabled  M.  Hebert  to  raise  the  number  to 
ninety,  and  he  first  pointed  out  that  most  of  them  agreed  specifically 
with  shells  of  Kleyn  Spawen,  near  Maestricht,  in  Belgium,  and  with 
those  of  Rupelmonde  and  other  places  near  Antwerp.  These  Belgian 
fossils  had  been  described  by  MM.  Nyst,  De  Koninck,  and  Bosquet,  and 
their  geological  position  had  been  accurately  ascertained  by  M.  Dumont, 
and  placed  by  him  above  the  Brussels  tertiary  beds,  which  are  the  un- 
doubted representatives  of  the  Calcaire  Grossier  of  Paris,  a  typical 
Eocene  group.  M.  de  Koninck,  about  the  same  time,  remarked  that 
the  Kleyn  Spawen,  or  "  Limburg"  fossils,  were  in  part  identical  with 
those  of  the  Mayence  tertiary  basin,  a  group  which  in  my  first  editions 
I  had  assigned  to  the  Miocene  period.  M.  Beyrich  more  recently  (1850) 
has  described  a  formation  of  the  same  age  as  that  of  Kleyn  Spawen, 
occurring  within  seven  miles  of  the  gates  of  Berlin,  near  the  village  of 
Hermsdorf ;  and  has  shown  that  about  a  third  of  the  species  agreed 
with  known  Belgian  shells  of  the  age  of  the  Gres  de  Fontainebleau, 
while  about  a  fifth  are  English  and  French  Middle  Eocene  species. 


CH.  XV.]  UPPER  EOCENE   FORMATIONS.  185 

In  1851,  I  examined  with  care  the  Belgian  formations  at  Rupelmonde 
and  Boom,  near  Antwerp,  and  in  the  Limburg,  near  Maestricht,  and 
was  able,  with  the  assistance  of  M.  Bosquet,  to  give  a  table  of  no  less 
than  201  species  of  shells  of  the  era  under  consideration.  Of  these  more 
than  a  third  proved  to  be  identical  with  English  Eocene  testacea,  even 
when  I  restricted  the  term  Eocene  to  its  most  limited  sense,  extending  it 
no  farther  upwards  than  the  Middle  Eocene  or  nummulitic  formations.* 
For  this  reason  I  called  the  Limburg  or  Kleyn  Spawen  beds  Upper 
Eocene,  giving  as  my  reason  "  that  they  resembled  the  older  formations 
in  their  fossils  as  much  as  some  of  the  different  divisions  of  the  Eocene 
series  in  France  and  England  resemble  each  other  ;  as  much,  for  exam- 
ple, as  the  Barton  Clay  in  Hampshire  agrees  with  the  London  Clay 
proper,  or  the  Calcaire  Grossier  with  the  Soissonnais  sands  in  France." 

Subsequently,  in  the  winter  of  1852,  Professor  Edward  Forbes  exam- 
ined near  Yarmouth,  in  the  Isle  of  Wight,  a  deposit  occupying  a  very 
limited  area,  but  about  170  feet  in  thickness,  which  he  first  determined 
to  be  of  the  same  age  as  the  Limburg  beds.  They  were  found  to  be  in 
conformable  position  with  the  other  tertiary  strata  previously  known  in 
that  island,  and  to  contain,  abundantly  some  of  the  most  characteristic 
Kleyn  Spawen  fossils.  He  named  this  deposit  "the  Hempstead  series," 
and  classed  it  as  Upper  Eocene,  for  reasons  similar  to  those  which  had 
induced  me  so  to  name  the  Limburg  beds  of  Belgium.  They  cannot  in 
fact  be  separated  from  the  subjacent  Eocene  strata  without  drawing  a 
line  of  demarcation  confessedly  arbitrary,  and  which  would  leave  a  great 
many  of  the  same  species  of  fossils  above  and  below  it.  So  complete, 
indeed,  is  the  passage  from  the  Bembridge  series  (an  equivalent  of  the 
gypsum  of  Montmartre,  and  therefore  an  acknowledged  Eocene  forma- 
tion) into  the  Hempstead  beds,  that  Professor  Forbes  places  both  groups 
together  in  his  Upper  Eocene  division,  drawing  the  line  between  Upper 
and  Middle  Eocene  at  the  base  of  the  Bembridge  beds. 

In  opposition  to  this  view  two  recent  authorities,  who  in  the  course  of 
the  present  year  (1853)  have  written  on  the  tertiary  formations  of  Ger- 
many, M.  Beyrich,  before  cited,f  and  Dr.  SandbergerJ  contend  that  all 
strata,  parallel  in  age  with  the  Limburg,  should  be  termed  Lower-  Mio- 
cene. M.  Beyrich  affirms  that  if  the  strata  of  the  Bolderberg  in  Bel- 
gium, and  numerous  deposits  of  contemporaneous  date  of  Northern 
Germany  already  enumerated  (p.  178),  be  of  the  age  of  the  "faluns," 
then  it  can  be  shown  that  these  same  beds  have  so  many  fossils  in 
common  with  the  Limburg  strata,  that  the  latter  may  fairly  be  regarded 
as  Miocene,  or  as  an  older  deposit  of  the  same  great  period ;  and  he 
goes  on  to  say  that,  unless  we  are  prepared  to  allow  the  Eocene  division 
to  absorb  all  the  overlying  tertiary  formations,  we  must  begin  a  new 
series  from  the  base  of  the  Limburg  upwards,  calling  the  latter  Lower 

*  Quart.  Geol.  Journ.  1852,  vol.  riii.  p.  322. 

f  Die  Conchylien  des  Xorddeutsch.  Tertiiirgeb. :  Berlin,  1853. 

t  Uber  das  Mainzer  Tertiarbeckens,  &c.  :  Wiesbaden,  1853. 


186      SEPARATION  OF  EOCENE  AND  MIOCENE  STRATA.     [On.  XV 

Miocene.  Dr.  Sandberger  divides  the  strata  of  the  Mayence  basin  into 
two  sections,  an  older  and  a  newer,  the  former  confessedly  the  equiva- 
lent of  the  Limburg  (or  Hempstead)  beds,  while  in  the  upper  he  find., 
some  fossil  remains,  which  appear  to  him  to  have  a  more  modern  char 
acter.  But  when  we  separate  from  this  higher  division  the  sands  c 
Eppelsheim,  containing  bones  of  Deinotherium  and  Mastodon  longirostrit 
which  are  most  probably  of  falunian  age,  the  rest  of  his  upper  seriei 
may  be  as  old  as  the  Limburg  beds,  though,  for  want  of  good  sections, 
there  is  much  obscurity  in  regard  to  the  grouping  of  the  beds.  Dr. 
Sandberger,  however,  gives  a  list  of  twelve  shells,  besides  some  teeth  ol 
fish  and  other  fossils,  which  are  common  to  the  Mayence  basin  and  the 
Hesse-Cassel  sands.  Now  the  latter  were  classed  as  Subapennine  or 
Pliocene  by  Philippi,  and,  although  we  have  as  yet  no  sufficient  data 
^or  determining  their  true  age,  appear  clearly  to  belong  to  a  more  mod- 
ern fauna  than  that  of  the  Mayence  basin.  If  such  a  relationship  could 
be  established  between  the  two  as  to  indicate  a  passage  from  the  Hesse- 
Cassel  fauna  to  that  of  the  Mayence  beds,  this  fact  would  doubtless  go 
some  way  towards  bearing  out  the  views  of  the  author. 

The  reader  has  probably  by  this  time  begun  to  perceive  that  one 
cause  of  embarrassment,  experienced  in  the  classification  of  these  ter- 
tiary formations,  arises  from  the  discovery  of  several  missing  links  in  the 
chain  of  historical  records.  I  may  remind  him  that  for  more  than 
twenty  years  I  have  advocated  in  the  Principles  of  Geology  the  doctrine 
that  there  has  been  a  continual  coming  in  of  new  species,  and  dying  oui, 
of  old  ones,  and  a  gradual  change  in  the  physical  geography  and  cli- 
mate of  the  earth,  and  not  such  a  reiteration  of  sudden  revolutions  in  the 
animate  and  inanimate  worlds,  as  was  once  insisted  upon  by  many  Eng- 
lish geologists  of  note,  and  is  still  maintained  by  not  a  few  of  the  most 
distinguished  continental  writers.  When,  therefore,  I  proposed  in  1833 
the  term  Miocene  for  the  faluns  of  Touraine,  the  fossil  shells  of  which, 
according  to  the  determination  of  M.  Deshayes,  contained  an  admixture 
of  about  seventeen  in  the  hundred  of  recent  species,  I  foretold  that  from 
time  to  time  new  sets  of  strata  would  come  to  light,  and  require  to  be 
intercalated  between  those  already  described,  and  in  that  case  that  the 
fossils  of  newly-found  beds  would  "  deviate  from  the  normal  types  first 
selected,  and  approximate  more  and  more  to  the  types  of  the  ante- 
cedent or  subsequent  epochs."  According  to  this  view,  it  was  obvious 
from  the  first  that  the  oldest  Miocene  records,  whenever  they  were 
detected,  would  not  be  easily  distinguishable  from  the  youngest 
members  of  the  Eocene  series,  especially  in  the  proportion  of  the 
living  to  the  extinct  species  of  fossil  shells.  The  importance,  indeed, 
of  the  latter  test  must  diminish  rapidly  the  more  we  recede  from 
the  Pliocene  and  approach  the  Miocene,  and  still  more  the  Eocene  for- 
mations, although  it  is  never  without  its  value,  and  often  furnishes 
the  only  common  standard  of  comparison  between  strata  of  very  distant 
countries.  ' 

I  make  these  allusions  to  show  that  I  am  by  no  means  unprepared 


Ca  XV.]  EOCENE  AND  MIOCENE  STRATA.  187 

for  the  discovery  of  gradations  from  Miocene  to  Eocene,  and  for  the 
probable  necessity  of  including  hereafter  in  the  Miocene  series  some 
fossiliferous  groups  which  may  diverge  in  their  characters  from  the 
standard  first  set  up,  or  from  the  type  of  the  faluns  of  Touraine.  But  I 
have  seen,  as  yet,  no  sufficient  evidence  that  such  a  passage,  as  is  here 
spoken  of,  has  been  made  out.  The  limits  of  the  Eocene  series  have 
been  extended,  without  as  yet  filling  up  the  gap  between  that  series 
and  the  faluns  of  Touraine.  I  am  desirous  at  the  same  time  to  explain, 
that  the  important  point  now  at  issue  is  not  simply  one  of  nomenclature. 
The  difficulty  is  the  same,  whether  we  use  the  terms  Lower  and  Middle 
Tertiary,  or  Eocene  and  Miocene.  To  one  or  other  of  the  periods  so  named 
we  must  refer  the  Limburg  and  Hempstead  beds,  and  the  sands  of  the 
Forest  of  Fontainebleau.  Can  we,  without  doing  violence  to  paleonto- 
logical  principles,  refer  all  these  to  the  same  period  as  the  faluns  of 
Touraine  ?  If  so,  it  would  be  immaterial  whether  we  called  them 
Middle  Tertiary,  Miocene,  or  "  Falunian,"  or  by  any  other  general  name. 
The  question  is,  whether,  in  the  present  state  of  our  information,  the 
mass  of  characteristic  fossils  of  the  groups  alluded  to  resemble  more 
nearly  the  Eocene  or  the  Falunian.  I  adhere  at  present  to  the  nomen- 
clature formerly  adopted  by  me  for  strata  described  in  this  chapter, 
calling  them  Upper  Eocene — not  because  of  the  small  number  of  living 
species  of  shells  found  in  them,  although  this  is  certainly  one  point  of 
agreement  between  them  and  the  "  nummulitie"  Eocene  beds,  but  be- 
cause of  the  aspect  of  the  whole  fauna,  which  seems  to  me  to  be  Eocene 
rather  than  Falunian.  Among  other  illustrations  of  this  affinity,  I  may 
refer  the  reader  to  the  numerous  and  excellent  figures  of  species  of  the 
genus  Valuta  given  by  M.  Beyrich  from  the  Limburg  beds  of  North 
Germany — forms  strikingly  characteristic  of  the  Barton  clay  in  Hamp- 
shire, a  regular  member  of  the  Middle  Eocene  group.  The  faluns  are 
devoid  of  such  forms.  Until,  therefore,  the  time  arrives  when  the  break 
between  the  Limburg  beds  and  the  faluns  has  disappeared  more  com- 
pletely, it  appears  to  me  safer  to  include  the  Limburg  and  all  contem- 
poraneous formations  in  the  Eocene. 

At  the  same  time  I  have  drawn  the  line  between  Middle  and  Upper 
Eocene,  as  in  former  editions,  excluding  from  the  latter  the  Bembridge 
beds  of  the  Isle  of  Wight,  or  the  gypseous  series  of  Montmartre.  A 
preference  is  given  to  this  last  method,  simply  for  convenience  sake,  in 
order  that  the  Upper  Eocene  of  this  work  may  coincide  exactly  with 
the  strata  classed  by  so  many  distinguished  geologists  as  Lower  Miocene. 
I  am  bound,  however,  to  state,  that  the  parting  line  between  the  Bem- 
bridge and  Hempstead  series,  in  the  Isle  of  Wight,  has  been  shown  by 
Professor  Forbes  to  be  an  arbitrary  one — a  purely  conventional  line, 
if  any  thing,  less  marked  than  the  line  separating  the  Bembridge  series 
from  the  underlying  St.  Helen's  group.  (See  Table,  p.  209.)  If  re- 
tained as  more  useful,  it  is,  as  before  hinted,  for  the  sake  of  confor- 
mity with  a  system  of  classification  adopted  by  many  able  geologists, 
who  selected  it  before  the  uninterrupted  continuity  of  the  Eocene  series 


188  LIMBURG  STRATA  IN  BELGIUM.  [On.  XV 

from  its  nummulitic  or  central  portions  to  its  Upper  or  Limburg  beds 
was  clearly  made  out. 

LIMBUR&  STRATA  IN  BELGIUM. 

(Rupflian  and  Tongrian  Systems  of  Dumont.) 

The  best  type  which  we  as  yet  possess  of  the  Upper  Eocene,  as  defined 
in  the  foregoing  observations,  consists  of  the  beds  formerly  known  to  col- 
lectors as  those  of  Kleyn  Spawen.  These  can  be  best  studied  in  the 
environs  of  the  village  so  named,  which  is  situated  about  seven  miles 
west  of  Maestricht,  and  in  the  old  province  of  Limburg  in  Belgium.  In 
that  region,  about  200  species  of  testacea,  marine  and  freshwater,  have 
been  obtained,  with  many  foraminifera  and  remains  of  fish. 

The  following  table  will  show  the  position  of  the  Limburg  beds. 

MIOCENE. 
A.  Bolderberg  beds,  see  p.  178,  seen  near  Hasselt. 

UPPER  EOCENE. 

B.  1.  Nucula  Loam  of  Kleyn  Spawen,  same  )  Upper  Limburg  beds. — Rupelian 
age  as  clay  of  Rupelmonde  and  Boom.  J  of  Duinont. 

B.  2.  Fluvio-marine  beds  of  Bergh,  Lethen,  )  Middle  Limburg  beds.  —  Upper 
and  other  places  near  Kleyn  Spawen.  y  Tongrian  of  Dumont. 

B.  3.  Green  sand  of  Bergh,  Neerepen,  &c.,  )  Lower  Limburg  Beds. — Lower 
near  Kleyn  Spawen  :  Marine.  y  Tongrian  of  Dumont. 

MIDDLE  EOCENE. 

C.  Lacken   and  Brussels  beds,  with  num- 
mulites,  &c. :  Louvaiu  and  Brussels. 

The  uppermost  of  the  three  subdivisions  (B.  1)  into  which  the  Limburg 
series  is  separated  in  the  abov  3  table,  contains  at  Kleyn  Spawen  many  of 
the  same  fossils  as  the  clay  o:  Rupelmonde  and  Boom,  ten  miles  south  of 
Antwerp,  and  sixty  miles  N.  W.  of  Kleyn  Spawen.  About  forty  species 
of  shells  have  been  collected  from  the  tile-clay  worked  on  the  banks  of 
the  Scheldt  at  the  villages  above  mentioned.  At  Rupelmonde,  this  clay 
attains  a  thickness  of  about  100  feet,  and  much  resembles  in  mineral 
character  the  "  London  Clay,"  containing  like  it  septaria  or  concretions  of 
argillaceous  limestone  traversed  by  cracks  in  the  interior.  The  shells 
have  been  described  by  MM.  Nyst  and  De  Koninck.  Among  them 
Leda  (or  Nucula)  Deshayesiana  (see  fig.  167)  is  by  far  the  most  abun- 

Fig.  167. 


Leda  Deshayesiana.    Nyst    Syn.  Nueula,  Deshayesiana. 


CH.  XV.]  STEATA  IX  NORTH  GER3IAXY.  189 

dant ;  a  fossil  unknown  as  yet  in  the  English  tertiary  strata,  but  when 
young  much  resembling  Leda  amygdaloides  of  the  London  clay  proper 
(see  fig.  227,  p.  218).  Among  other  characteristic  shells  are  Pecten 
Hoeninghausii,  and  a  species  of  Cassidaria,  and  several  of  the  genus 
Pleurotoma.  Not  a  few  of  these  testacea  agree  with  English  Eocene 
species,  such  as  Actceon  simulatus,  Sow.,  Cancellaria  evulsa,  Brander, 
Corbula  pisum  (fig.  170,  p.  193),  and  Nautilus  ziczac.  They  are  accom- 
panied by  many  teeth  of  sharks,  as  Lamna  contortidens,  Ag.,  Oxyrhina 
riphodon,  Ag.,  Carcharodon  heterodon  (see  fig.  211),  Ag.,  and  other  fish, 
some  of  them  common  to  the  Middle  Eocene  strata.  The  same  deposit, 
B.  1,  is  very  imperfectly  seen  at  Kleyn  Spawen,  where  the  lower  divisions 
B.  2  and  B.  3  are  much  better  developed.  B.  2  consists  of  several  alter- 
nations of  sands  and  marls,  in  which  a  greater  or  less  intermixture  of 
fluviatile  and  marine  shells  occurs,  implying  the  occasional  entrance  of  a 
river  near  the  spot,  and  possibly  oscillations  in  the  level  of  the  bottom  of 
the  sea.  Among  the  shells  are  found  Cyrena  semistriata  (fig.  171,  p. 
193),  Cerithium  plicatum,  Lam.  (fig.  172,  p.  193),  Rissoa  Cliastelii, 
Bosq.  (fig.  174),  and  Corbula  pisum  (fig.  170),  four  shells  all  common  to 
the  Hempstead  beds  in  the  Isle  of  Wight,  to  be  mentioned  in  the  sequel. 
With  the  above,  Lucina  Thierensii,  and  other  marine  forms  of  the  genera 
Venus,  Limopsis,  Trochus,  &c.,  are  met  with. 

In  B.  3,  or  the  Lower  Limburg,  more  than  100  marine  shells  have  been 
collected,  among  which  the  Ostrea  ventilabrum  is  very  conspicuous.  Spe- 
cies common  to  the  underlying  Brussels  sands,  or  the  Middle  Eocene,  are 
numerous,  constituting  a  third  of  the  whole  ;  but  most  of  these  are  feebly 
represented  in  comparison  with  the  more  peculiar  and  characteristic  shells, 
such  as  Ostrea  ventilabrum,  Mytilus  Nystii,  Valuta  saturalis,  &c. 

In  none  of  the  Belgian  Upper  Eocene  strata,  could  I  find  any  nummu- 
lites ;  and  M.  D'Archiac  had  previously  observed  that  these  foraminifera 
characterize  his  "  Lower  Tertiary  Series,"  as  contrasted  with  the  Middle, 
anc  tTould  therefore  serve  as  a  good  test  of  age  between  Eocene  and  Mio- 
cene, if  the  line  of  demarcation  be  drawn  according  to  his  method,  or 
equally  so  between  Upper  and  Middle  Eocene,  according  to  the  plan 
adopted  in  this  work.  The  same  naturalist  informs  us  that  one  nummu- 
lite  only  has  ever  yet  been  seen  to  penetrate  upwards  into  the  middle 
tertiary,  viz.,  Nummulites  intermedia,  an  Eocene  species.  It  has  been 
found  in  the  hill  of  the  Superga  near  Turin,*  in  beds  usually  classed  as 
Miocene,  but  probably  somewhat  older  than  the  falunian  type. 

Hermsdorf,  near  Berlin. — Professor  Beyrich  has  described  a  mass  of 
clay,  used  for  making  tiles  within  seven  miles  of  the  gates  of  Berlin,  near 
the  village  of  Hermsdorf,  rising  up  from  beneath  the  sands  with  which 
that  country  is  chiefly  overspread.  This  clay  is  more  than  forty  feet 
thick,  of  a  dark  bluish-gray  color,  and,  like  that  of  Rupelmonde,  contains 
septaria.  Among  othervshells,  the  Leda  Deshayesiana  before  mentioned 
(fig.  167)  abounds,  together  with  many  species  of  Pleurotoma,  Voluta,  &c., 

*  Archiac,  Monogr.  pp.  79,  100. 


190  MAYENOE  BASIN.  [On.  XV. 

a  certain  proportion  of  the  fossils  being  identical  in  species  with  Limburg 
and  Mayence  shells. '  M.  Beyrich  enumerates  several  other  localities  in 
North  Germany,  and  particularly  one  at  Magdeburg,  and  several  on  the 
Lower  Elbe,  where  beds  of  the  same  age  appear. 

Mayence  basin. — I  have  already  alluded  to  the  elaborate  description 
published  by  Dr.  F.  Sandberger  of  the  Mayence  tertiary  area,  which  oc- 
cupies a  tract  from  five  to  twelve  miles  in  breadth,  extending  for  a  great 
distance  along  the  left  bank  of  the  Rhine  from  Mayence  to  the  neighbor- 
hood of  Manheim,  and  which  is  also  found  to  the  east,  north,  and  south- 
west of  Frankfort.  M.  De  Koninck,  of  Liege,  first  pointed  out  to  me  that 
the  purely  marine  portion  of  the  deposit  (the  Lower  group  of  Dr.  Sand- 
berger) contained  many  species  of  shells  common  to  the  Limburg  beds 
near  Kleyn  Spawen,  and  to  the  clay  of  Rupelmonde,  near  Antwerp. 
Among  these  he  mentioned  Cassidaria  depressa,  Tritonium  argutum, 
Brander  ( T.  flandricum,  De  Koninck),  Tornatella  simulata,  Rostellaria 
Sowerbyi,  Leda  Deshayesiana  (fig.  167,  p.  188),  Corbula  pisum  (fig.  1*70), 
and  Pectunculus  terebratularis. 

The  marine  beds  are  in  some  places  covered  with  brackish-water 
marls  containing  Cyrence  in  great  numbers,  among  which  Cyrena  semis- 
triata  occurs,  with  Cerithium  plicatum,  Corbulomya  triangula,  Mytilus 
Fanjasii,  and  other  Limburg  and  Hempstead  shells.  Perna  Soldani,  a 
shell  of  the  upper  Eocene  or  Merignac  beds  of  the  Bourdeaux  basin,  but 
also  a  Vienna  basin  shell,  is  characteristic  both  of  the  marine  and  brackish 
series.  Two  species  of  Anthracotherium,  A.  magnum,  Cuv.,  and  A.  al- 
saticum,  are  met  with  in  the  same  deposits. 

The  upper  portion  of  this  Mayence  series  has  at  its  base  a  limestone 
full  of  Cerithia  and  land-shells  ;  among  which  Cerithium  plicatum  before 
mentioned,  and  another  Limburg  shell,  Venus  incrassata,  Sow.,  a  fossil 
common  to  the  Headon  or  Middle  Eocene  of  England,  are  met  with ;  alsc 
Neritina  concava  (fig.  194),  a  Middle  Eocene  shell,  and  Rhinoceros  in- 
cisivus,  the  oldest  form  of  that  genus,  and  called  by  Kaup  Acerotherium. 
Next  above  is  a  limestone,  in  which  Littorinella  or  Paludina  inflata  is  a 
very  common  fossil,  with  others  of  the  same  genus.  One  of  these,  very 
nearly  resembling  the  recent  Littorinella  ulva,  is  found  through- 
out this  basin.  These  shells  are  like  grains  of  rice  in  size,  and  Fig%  16S* 
are  often  in  such  quantity  as  to  form  entire  beds  of  marl  and 
limestone,  in  stratified  masses  from  fifteen  to  thirty  feet  in 
thickness,  just  as  in  the  Baltic  modern  accumulations  several 
feet  thick  of  the  Littorinella  ulva  are  spread  far  and  wide  over 
the  bottom  of  the  sea.  In  the  same  beds,  several  species  of 
Dreissena  abound,  a  form  common  to  the  Headon  or  Middle  Eocene  beds 
of  the  Isle  of  Wight,  as  well  as  to  the  existing  seas.  On  the  whole,  I  am 
not  satisfied  that  this  fauna  diverges  from  the  Limburg  type  towards  that 
of  the  faluns  as  much  as  Dr.  Sandberger  believes.  Among  the  Mammalia, 
we  find  Hippotherium  gracile,  Acerotherium  (or  Rhinoceros)  incisivum, 
Paleomeryx,  Chalicomys,  &c.  Lastly,  the  Eppelsheim  sand  overlies  the 
whole,  containing  Deinotherium  giganteum,  and  some  other  true  Miocene 


CH.  XV.] 


BROWN   COAL   OF   GERMANY. 


191 


quadrupeds.  Several  mammalia,  proper  to  the  Upper  Eocene  series,  are 
also  said  to  be  associated  ;  but  there  being  no  good  section  at  Eppelsheim, 
the  true  succession  of  the  beds  from  which  the  bones  were  dug  out  cannot 
be  seen,  and  we  have  yet  to  learn  whether  some  remains  of  an  older  series 
may  not  have  been  confounded  with  those  of  a  newer  one. 

Brown  coal  of  Germany. — In  a  recent  essay  on  the  Brown  Coal  de- 
posits of  Germany,  Baron  Von  Buch  has  expressed  a  decided  opinion 
that  they  all  belong  to  one  epoch,  being  of  subsequent  date  to  the  great 
nummulitic  period,  and  older  than  the  Pliocene  formations.  He  has 
therefore  called  the  whole  Miocene.  Unfortunately,  these  formations 
rarely  contain  any  internal  evidence  of  their  age,  except  what  may  be 
derived  from  plants,  constituting  in  every  case  but  a  fraction  of  an 
ancient  Flora,  and  consisting  of  mere  leaves,  without  flowers  or  fruits. 
It  is  often  therefore  impossible  to  form  more  than  a  conjecture  as  to 
the  precise  place  in  the  chronological  series  which  should  be  assigned 
to  each  layer  of  lignite  or  each  leaf-bed.  Nevertheless,  enough  is  known 
to  show  that  some  of  the  Brown  Coals  found  in  isolated  patches  be- 
long to  the  Upper  Eocene,  others  to  the  Miocene,  and  some  perhaps 
to  the  Pliocene  eras.  They  seem  to  have  been  formed  at  a  period  when 
the  European  area  had  already  a  somewhat  continental  character,  so  that 
few  contemporaneous  marine  or  even  fluvio  marine  beds  were  in  progress 
there. 

The  brown  coal  of  Brandenburg,  on  the  borders  of  the  Baltic,  under- 
lies the  Hermsdorf  tile-clay  already  spoken  of,  and  therefore  belongs  to 
a  period  at  least  as  old  as  the  Upper  Eocene.  The  brown  coal  of 
Radoboj,  on  the  confines  of  Styria,  is  covered,  says  Von  Buch,  by  beds 
containing  the  marine  shells  of  the  Vienna 
basin,  which,  as  before  remarked,  are  chiefly 
of  the  Falunian  or  Miocene  type.  This 
lignite,  therefore,  may  be  of  Miocene  or 
Upper  Eocene  date,  a  point  to  be  deter- 
mined by  the  botanical  characters  of  the 
plants.  In  this,  and  most  of  the  principal 
brown  coal  formations,  several  species  of 
fan-palm  or  Flabellaria  abound.  This  genus 
also  appears  in  the  Middle  Eocene  or  Bern- 
bridge  beds  in  the  Isle  of  Wight,  and  in  the 
gypseous  series  of  Montmartre ;  but  it  is  still 
more  largely  represented  in  the  Upper  Eo- 
cene series,  accompanied  by  palms  of  the 
genus  Phoenicites.  Various  cones,  and  the 
leaves  and  wood  of  coniferous  trees,  are  also 
met  with  at  Radoboj.  Species  also  of 
Comptonia  and  Myrica,  with  various  trees, 
such  as  the  plane  or  Platanus,  are  recog- 
nized by  their  leaves,  as  also  several  of  the  Laurel  tribe,  especially  one, 
called  Daphnogene  cinnamomifolia  (fig.  169)  by  Unger,  who,  together 


Fig.  169. 


Daphnogene  cinnamomifolia, 
Altsattel,  in  Bohemia. 


192  UPPER  EOCENE  STEATA  OF  ENGLAND.  [On.  XV. 

with  Goppert,  has  investigated  the  botany  of  these  formations.  It  will 
be  seen  that  in  the  leaf  of  this  Daphnogene  two  veins  branch  off  on 
each  side  from  the  mid-rib,  and  run  up  without  interruption  to  the 
point. 

On  the  Lower  Rhine,  whether  in  the  Mayence  basin  or  in  the  Sieben- 
gebirge,  and  in  the  neighborhood  of  Bonn  and  Cologne,  there  seem  to 
be  Brown  Coals  of  more  than  one  age.  Von  Buch  tells  us  that  the 
only  fossil  found  in  the  Brown  Coal  near  Cologne,  one  often  met  with 
there  in  the  excavation  of  a  tunnel,  is  the  peculiar  fruit,  so  like  a  cocoa- 
nut,  called  Nipadites  or  Burtonia  Fanjasii  (see  fig.  220).  Now  this 
fossil  abounds  in  the  Lower  Eocene  or  Sheppy  clay  near  London,  also 
in  the  Middle  Eocene  at  Brussels;  and  I  found  it  still  higher  in  the 
same  nummulitic  series  at  Cassel,  in  French  Flanders.  This  fact  taken 
alone  would  rather  lead  us  to  refer  the  Cologne  lignite  to  the  Eocene 
period. 

Some  of  the  lignites  of  the  Siebengebirge  near  Bonn  associated  with 
volcanic  rocks,  and  those  of  Hesse  Cassel  which  accompany  basaltic  out- 
pourings, are  certainly  of  much  later  date. 

UPPER  EOCENE  STRATA  OP  ENGLAND. 

Hempstead  beds. — Isle  of  Wight. — Until  veiy  lately  it  was  supposed 
by  English  geologists  that  the  newest  tertiary  strata  of  the  Isle  of  Wight 
corresponded  in  age  with  the  gypseous  series  of  Montrnartre  near  Paris  ; 
and  this  idea  was  confirmed  by  the  fact  that  the  same  species  of  Palceo- 
therium,  Anoplotherium,  and  other  extinct  mammalia  so  characteristic  of 
the  Parisian  series,  were  also  found  at  Binstead,  near  Hyde,  in  the  north- 
ern district  of  the  island,  forming  part  of  the  fluvio-marine  series.  We 
are  indebted  to  Prof.  E.  Forbes  for  having  discovered  in  the  autumn  of 
1852  that  there  exist  three  formations,  the  true  position  of  which  had 
been  overlooked,  all  of  them  newer  than  the  beds  of  Headon  Hill,  in 
Alum  Bay,  which  last  were  formerly  believed  to  be  the  uppermost  part  of 
the  Isle  of  Wight  tertiary  series.* 

The  three  overlying  formations  to  which  I  allude  are  as  follows  : — 
1st,  certain  shales  and  sandstones  called  the  St.  Helen's  beds  (see 
Table,  p.  104,  et  seq.)  rest  immediately  upon  the  Headon  series ;  2dly, 
the  St.  Helen's  series  is  succeeded  by  the  Bembridge  beds  before  men- 
tioned, the  equivalent  of  the  Montmartre  gypsum ;  and  3dly,  above 
the  whole  is  found  the  Upper  Eocene  or  Hempstead  series.  This  newer 
deposit,  which  is  170  feet  thick,  has  been  so  called  from  Hempstead 
Hill,  near  Yarmouth,  in  the  Isle  of  Wightf  The  following  is  the  suc- 
cession of  strata  there  discovered,  the  details  of  which  are  important 
for  reasons  explained  in  the  preliminary  remarks  of  this  chapter  (p. 
187)  :— 

*  E.  Forbes,  Geol.  Quart.  Journ.  1853. 

\  This  hill  must  not  be  confounded  with  Hampstead  Hill,  near  London,  where 
the  Lower  Eocene  or  London  Clay  is  capped  by  Middle  Eocene  sands. 


CH.  XV.] 


UPPER  EOCENE,  ISLE  OF  WIGHT. 


193 


SUBDIVISIONS  OF  THE  HEMPSTEAD  SERIES. 


1.  The  uppermost  or  Corbula  beds,  consisting  of  marine  sands  and  clays,  contain 
Corbula  pisum,  fig.  170,  a  species  common  to  the  Middle  Eocene  clay  of 
Barton;  Cyrena  semistriata,  fig.  1 71,  which  is  also  a  Middle  Eocene  fossil; 
several  Cerithia,  and  other  shells  peculiar  to  this  series. 


Fig.  170. 


Fig.  171. 


Corbula  pisum,    Hempstead  Beds, 
Isle  of  Wight 


Cyrena  semistriata. 
Hempstead  Beds. 


2.  Next  below  are  freshwater  and  estuary  marls  and  carbonaceous  clays,  in  the 
brackish-water  portion  of  which  are  found  abundantly  Cerithium  plicatum, 
Lam.,  fig.  172,  C.  elegans,  fig.  173,  and  C.  tricinctum ;  also  Rissoa  Chastelii, 
fig.  174,  a  very  common  Limburg  shell,  and  which  occurs  in  each  of  the  four 
subdivisions  of  the  Hempstead  series  down  to  its  base,  where  it  passes  into 
the  Bembridge  beds.  In  the  freshwater  portion  of  the  same  beds  Paludina 


Fig.  172. 


Fig.  173. 


Fig.  174 


Fig.  175. 


Cerithium  plicatum,      Cerithium  elegans,      Ris»oa  Chastelii,  Nyst, 
Lam.  Hempstead.  Hempstead.  Sp.  Hempstead,  Isle 


Paludina  lenta. 
Hempstead  Beds. 


lent  a,  fig.  175,  occurs  a  shell  identified  by  some  conchologists  with  a  species 
now  living,  P.  unicolor  ;  also  several  species  of  Lymneus,  Planorbis,  and  Unio. 

8.  The  next  series,  or  middle  freshwater  and  estuary  marls,  are  distinguished  by 
the  presence  of  Melania  fasciata,  Paludina  lenta,  and  clays  with  Cypris  ;  the 
lowest  bed  contains  Cyrena  semistriata,  fig.  171,  mingled  with  Cerithia  and  a 
Panopcea. 

4.  The  lower  freshwater  and  estuary  marls  contain  Melania  costata,  Sow.,  Me- 
lanopsis,  &c.  The  bottom  bed  is  carbonaceous,  and  called  the  "Black  band," 
in  which  Jtissoa  Chastelii,  fig.  173,  before  alluded  to,  is  common.  This  bed 
contains  a  mixture  of  Hempstead  shells  with  those  of  the  underlying  Middle 
Eocene  or  Bembridge  series.  The  seed-vessels  of  Char  a  medicaginula,  Brong., 
and  C.  helecteras  are  characteristic  of  the  Hempstead  beds  generally.  The 
mammalia,  among  which  is  a  species  of  Hyotherium,  differ,  so  far  as  they  are 
known,  from  those  of  the  Bembridge  beds  immediately  underlying. 

13 


194  UPPER  EOCENE   STRATA   OF   FRANCE.  [On.  XV 

Between  the  Hempstead  beds  above  described  and  those  next  below  them,  there 
is  no  break,  as  before  stated,  p.  187.  The  freshwater,  brackish,  and  marine 
limestones  and  marls  of  the  underlying  or  Bembridge  group  are  in  conformable 
stratification,  and  contain  Cyrena  semistriata,  fig.  171,  Melania  muricata,  Pain- 
dina  lenta,  fig.  175,  and  several  other  shells  belonging  to  the  Hempstead  beds. 
Prof.  Forbes  therefore  classes  both  of  them  in  the  same  Upper  Eocene  division. 
I  have  called  the  Bembridge  beds  Middle  Eocene,  for  convenience  sake,  as 
already  explained  (pp.  183,  187.) 

UPPER  EOCENE  STRATA  OF  FRANCE. 

(Lower  Miocene  of  many  French  authors) 

The  Gres  de  Fontainebleau,  or  sandstone  of  the  Forest  of  Fontainebleau, 
has  been  frequently  alluded  to  in  the  preceding  pages,  as  corresponding 
in  age  to  the  Limburg  or  Hempstead  beds.  It  is  associated  in  the  sub- 
urbs of  Paris  with  a  set  of  strata,  very  varied  in  their  composition,  and 
containing  in  their  lower  portion  a  green  clay  with  abundance  of  small 
oysters  (Ostrea  cyathula,  Lam.)  which  are  spread  over  a  wide  area.  The 
marine  sands  and  sandstone  which  overlie  this  clay  include  Cytherea  in- 
crassata  and  many  other  Limburg  fossils,  the  finest  collections  of  which 
have  been  made  at  Etampes,  south  of  Paris,  where  they  occur  in  loose 
sand.  The  Gres  de  Fontainebleau  is  sometimes  called  the  "  Upper  marine 
sands"  to  distinguish  it  from  the  "  Middle  sands"  or  Gres  de  Beauchamp, 
a  Middle  Eocene  group. 

Calcaire  lacustre  superieur. — Above  the  Gres  de  Fontainebleau  is  seen 
the  upper  freshwater  limestone  and  marl,  sometimes  called  Calcaire  de  la 
Beauce,  which  with  its  accompanying  marls  and  siliceous  beds  seem  to 
have  been  formed  in  marshes  and  shallow  lakes,  such  as  frequently  over- 
spread the  newest  parts  of  great  deltas.  Beds  of  flint,  continuous  or  in 
nodules,  accumulated  in  these  lakes,  and  Charce,  aquatic  plants,  already 
alluded  to,  left  their  stems  and  seed-vessels  imbedded  both  in  the  marl 
and  flint,  together  with  freshwater  and  land-shells.  Some  of  the  siliceous 
rocks  of  this  formation  are  used  extensively  for  millstones.  The  flat  sum- 
mits or  platforms  of  the  hills  round  Paris — large  areas  in  the  forest  of 
Fontainebleau,  and  the  Plateau  de  la  Beauce,  between  the  Seine  and  the 
Loire,  are  chiefly  composed  of  these  upper  freshwater  strata.  When  they 
reach  the  valley  of  the  Loire,  they  occasionally  underlie  and  form  the 
boundaiy  of  the  marine  Miocene  faluns,  fragments  of  the  older  freshwater 
limestone  having  been  broken  off  and  rolled  on  the  shores  and  in  the  bed 
of  the  Miocene  sea,  as  at  Pontlevoy,  on  the  Cher,  where  the  perforating 
marine  shells  of  the  Miocene  period  still  remain  in  hollows  drilled  in  the 
blocks  of  Eocene  limestone. 

Central  France. — Lacustrine  strata,  belonging,  for  the  most  part,  to 
the  same  Upper  Eocene  series,  are  again  met  with  in  Auvergne,  Cantal, 
and  Velay,  the  sites  of  which  may  be  seen  in  the  annexed  map.  They 
appear  to  be  the  monuments  of  ancient  lakes,  which,  like  some  of  those 
now  existing  in  Switzerland,  once  occupied  the  depressions  in  a  mountain- 
ous region,  and  have  been  each  fed  by  one  or  more  rivers  and  torrents. 


OH.  XV.]  UPPER   EOCENE   OF   CENTRAL   FRANCE.  195 


Fig.  176. 


196  SUCCESSION  OF   CHANGES  IN  AUVEKGNE.  [Cs.  XT 

The  country  where  they  occur  is  almost  entirely  composed  of  granite 
and  different  varieties  of  granitic  schist,  with  here  and  there  a  few 
patches  of  secondary  strata,  much  dislocated,  and  which  have  probably 
suffered  great  denudation.  There  are  also  some  vast  piles  of  volcanic 
matter  (see  the  map),  the  greater  part  of  which  is  newer  than  the  fresh- 
water strata,  and  is  sometimes  seen  to  rest  upon  them,  while  a  small  part 
has  evidently  been  of  contemporaneous  origin.  Of  these  igneous  rocks 
T  shall  treat  more  particularly  in  another  part  of  this  work. 

Before  entering  upon  any  details,  I  may  observe,  that  the  study  of 
these  regions  possesses  a  peculiar  interest,  very  distinct  in  kind  from  that 
derivable  from  the  investigation  either  of  the  Parisian  or  English  ter- 
tiary areas.     For  we  are  presented  in  Auvergne  with  the  evidence  of  a 
series  of  events  of  astonishing  magnitude  and  grandeur,  by  which  the 
original  form  and  features  of  the  country  have  been  greatly  changed, 
yet  never  so  far  obliterated  but  that  they  may  still,  in  part  at  least,  be 
restored  in  imagination.     Great  lakes  have  disappeared, — lofty  moun- 
tains have  been  formed,  by  the  reiterated  emission  of  lava,  preceded  and 
followed  by  showers  of  sand  and  scoriae, — deep  valleys  have  been  sub- 
sequently furrowed  out  through  masses  of  lacustrine  and  volcanic  origin, 
— at  a  still  later  date,  new  cones  have  been  thrown  up  in  these  valleys, — 
new  lakes  have  been  formed  by  the  damming  up  of  rivers, — and  more 
than  one  creation  of  quadrupeds,  birds,  and  plants,  Eocene,  Miocene,  and 
Pliocene,  have  followed  in  succession  ;  yet  the  region  has  preserved  from 
first  to  last  its  geographical  identity ;  and  we  can  still  recall  to  our 
thoughts   its   external   condition  and  physical   structure   before   these 
wonderful  vicissitudes  began,  or  while  a  part  only  of  the  whole  had 
been  completed.     There  was  first  a  period  when  the  spacious  lakes,  of 
which  we  still  may  trace  the  boundaries,  lay  at  the  foot  of  mountains  of 
moderate  elevation,  unbroken  by  the  bold  peaks  and  precipices  of  Mont 
Dor,  and  unadorned  by  the  picturesque  outline  of  the  Puy  de  Dome,  or 
of  the  volcanic  cones  and  craters  now  covering  the  granitic  platform. 
During  this  earlier  scene  of  repose  deltas  were  slowly  formed ;  beds  of 
marl  and  sand,  several  hundred  feet  thick,  deposited ;  siliceous  and  cal- 
careous rocks  precipitated  from  the  waters  of  mineral  springs  ;  shells  and 
insects  imbedded,  together  with  the  remains  of  the  crocodile  and  tor- 
toise, the  eggs  and  bones  of  water  birds,  and  the  skeletons  of  quadru- 
peds, some  of  them  belonging  to  the  same  genera  as  those  entombed  in 
the  Eocene  gypsum  of  Paris.     To  this  tranquil  condition  of  the  surface 
succeeded  the  era  of  volcanic  eruptions,  when  the  lakes  were  drained, 
and  when  the  fertility  of  the  mountainous  district  was  probably  enhanced 
by  the  igneous  matter  ejected  from  below,  and  poured  down  upon  the 
more  sterile  granite.     During  these   eruptions^  which  appear  to  have 
',aken  place  after  the  disappearance  of  the  upper  Eocene  fauna,  and  partly 
in  the  Miocene  epoch,  the  mastodon,  rhinoceros,  elephant,  tapir,  hippo- 
potamus, together  with  the  ox,  various  kinds  of  deer,  the  bear,  hyaena, 
and  many  beasts  of  prey,  ranged  the  forest,  or  pastured  on  the  plain,  and 
were  occasionally  overtaken  by  a  fall  of  burning  cinders,  or  buried  in 


OH.  XV.]  LACUSTRINE  STRATA — AUVERGNE.  197 

flows  of  mud,  such  as  accompany  volcanic  eruptions.  Lastly,  these  quad- 
rupeds became  extinct,  and  gave  place  to  Pliocene  mammalia  (see  chap. 
xxxii.V  and  these  in  their  turn,  to  species  now  existing.  There  are  no 
signs,  during  the  whole  time  required  for  this  series  of  events,  of  the  sea 
having  intervened,  nor  of  any  denudation  which  may  not  have  been  ac- 
complished by  currents  in  the  different  lakes,  or  by  rivers  and  floods  ac- 
companying repeated  earthquakes,  during  which  the  levels  of  the  district 
have  in  some  places  been  materially  modified,  and  perhaps  the  whole  up- 
raised relatively  to  the  surrounding  parts  of  France. 

Auvergne. — The  most  northern  of  the  freshwater  groups  is  situated  in 
the  valley-plain  of  the  Allier,  which  lies  within  the  department  of  the  Puy 
de  Dome,  being  the  tract  which  went  formerly  by  the  name  of  the  Li- 
magne  d' Auvergne.  It  is  inclosed  by  two  parallel  mountain  ranges, — 
that  of  the  Forez,  which  divides  the  waters  of  the  Loire  and  Allier,  on 
the  east ;  and  that  of  the  Monts  Domes,  which  separates  the  Allier  from 
the  Sioule,  on  the  west.*  The  average  breadth  of  this  tract  is  about  20 
miles ;  and  it  is  for  the  most  part  composed  of  nearly  horizontal  strata  of 
sand,  sandstone,  calcareous  marl,  clay,  and  limestone,  none  of  which  ob- 
serve a  fixed  and  invariable  order  of  superposition.  The  ancient  borders 
of  the  lake,  wherein  the  freshwater  strata  were  accumulated,  may  gen- 
erally be  traced  with  precision,  the  granite  and  other  ancient  rocks  rising 
up  boldly  from  the  level  country.  The  actual  junction,  however,  of  the 
lacustrine  and  granitic  beds  is  rarely  seen,  as  a  small  valley  usually  in- 
tervenes between  them.  The  freshwater  strata  may  sometimes  be  seen 
to  retain  their  horizontally  within  a  very  slight  distance  of  the  border- 
rocks,  while  in  some  places  they  are  inclined,  and  in  few  instances  vertical. 
The  principal  divisions  into  which  the  lacustrine  series  may  be  separated 
are  the  following ; — 1st,  Sandstone,  grit,  and  conglomerate,  including  red 
marl  and  red  sandstone.  2dly,  Green  and  white  foliated  marls.  3dly, 
Limestone  or  travertin,  often  oolitic.  4thly,  Gypseous  marls. 

1.  a.  Sandstone  and  conglomerate. — Strata  of  sand  and  gravel,  some- 
times bound  together  into  a  solid  rock,  are  found  in  great  abundance 
around  the  confines  of  the  lacustrine  basin,  containing,  in  different  places, 
pebbles  of  all  the  ancient  rocks  of  the  adjoining  elevated  country ;  namely, 
granite,  gneiss,  mica-schist,  clay-slate,  porphyry,  and  others,  but  without 
any  intermixture  of  basaltic  or  other  tertiary  volcanic  rocks.  These  strata 
do  not  form  one  continuous  band  around  the  margin  of  the  basin,  being 
rather  disposed  like  the  independent  deltas  which  grow  at  the  mouths  of 
torrents  along  the  borders  of  existing  lakes. 

At  Chamalieres,  near  Clermont,  we  have  an  example  of  one  of  these 
deltas,  or  littoral  deposits,  of  local  extent,  where  the  pebbly  beds  slope 
away  from  the  granite,  as  if  they  had  formed  a  talus  beneath  the  waters 
of  the  lake  near  the  steep  shore.  A  section  of  about  50  feet  in  vertical 
height  has  been  laid  open  by  a  torrent,  and  the  pebbles  are  seen  to  con- 
sist throughout  of  rounded  and  angular  fragments  of  granite,  quartz, 

*  Scrope,  Geology  of  Central  France,  p.  15. 


198  UPPER  EOCENE  PERIOD.          [Cn.  XV. 

primary  slate,  and  red  sandstone.  Partial  layers  of  lignite  and  pieces  of 
wood  are  found  in  these  beds. 

At  some  localities  on  the  margin  of  the  basin  quartzose  grits  are  found ; 
and,  where  these  rest  on  granite,  they  are  sometimes  formed  of  separate 
crystals  of  quartz,  mica,  and  felspar,  derived  from  the  disintegrated  granite, 
the  crystals  having  been  subsequently  bound  together  by  a  siliceous  ce- 
ment. In  these  cases  the  granite  seems  regenerated  in  a  new  and  more 
solid  form ;  and  so  gradual  a  passage  takes  place  between  the  rock  of 
crystalline  and  that  of  mechanical  origin,  that  we  can  scarcely  distinguish 
where  one  ends  and  the  other  begins. 

In  the  hills  called  the  Puy  de  Jussat  and  La  Roche,  we  have  the  advan- 
tage of  seeing  a  section  continuously  exposed  for  about  700  feet  in  thick- 
ness. At  the  bottom  are  foliated  marls,  white  and  green,  about  400  feet 
thick ;  and  above,  resting  on  the  marls,  are  the  quartzose  grits,  cemented 
by  calcareous  matter,  which  is  sometimes  so  abundant  as  to  form  imbed- 
ded nodules.  These  sometimes  constitute  spheroidal  concretions  6  feet  in 
diameter,  and  pass  into  beds  of  solid  limestone,  resembling  the  Italian 
travertins,  or  the  deposits  of  mineral  springs. 

1.  b.  Red  marl  and  sandstone. — But  the   most  remarkable   of  the 
arenaceous  groups  is  one  of  red  sandstone  and  red  marl,  which  are  iden- 
tical in  all  their  mineral  characters  with  the  secondary  New  Red  sand- 
stone and  marl  of  England.     In  these  secondary  rocks  the  red  ground  is 
sometimes  variegated  with  light  greenish  spots,  and  the  same  may  be 
seen  in  the  tertiary  formation  of  freshwater  origin  at  Coudes,  on  the  Al- 
lier.     The  marls  are  sometimes  of  a  purplish-red  color,  as  at  Champheix, 
and  are  accompanied  by  a  reddish  limestone,  like  the  well-known  "  corn- 
stone,"  which  is  associated  with  the  Old  Red  sandstone  of  English  geol- 
ogists.    The  red  sandstone  and  marl  of  Auvergne  have  evidently  been 
derived  from  the  degradation  of  gneiss  and  mica-schist,  which  are  seen 
in  situ  on  the  adjoining  hills,  decomposing  into  a  soil  very  similar  to  the 
tertiary  red  sand  and  marl.     We  also  find  pebbles  of  gneiss,  mica-schist, 
and  quartz  in  the  coarser  sandstones  of  this  group,  clearly  pointing  to 
the  parent  rocks  from  which  the  sand  and  marl  are  derived.     The  red 
beds,  although  destitute  themselves  of   organic  remains,  pass  upwards 
into  strata  containing  tertiary  fossils,  and  are  certainly  an  integral  part  of 
the  lacustrine  formation.     From  this  example  the  student  will  learn  how 
small  is  the  value  of  mineral  character  alone,- as  a  test  of  the  relative  age 
of  rocks. 

2.  Green  and  white  foliated  marls. — The  same  primary  rocks  of  Au- 
vergne, which,  by  the  partial  degradation  of  their  harder  parts,  gave  rise 
to  the  quartzose  grits  and  conglomerates  before  mentioned,  would,  by  the 
reduction  of  the  same  materials  into  powder,  and  by  the  decomposition 
of  their  felspar,  mica,  and  hornblende,  produce  aluminous  clay,  and,  if  a 
sufficient  quantity  of  carbonate  of  lime  was  present,  calcareous  marl. 
This  fine  sediment  would  naturally  be  carried  out  to  a  greater  distance 
from  the  shore,  as  are  the  various  finer  marls  now  deposited  in  Lake 
Superior.     And  as,  in  the  American  lake,  shingle  and  sand  are  annually 


CH.  XV.]  LACUSTRINE  STRATA — AUYERGNE.  199 

amassed  near  the  northern  shores,  so  in  Auvergne  the  grits  and  con- 
glomerates before  mentioned  were  evidently  formed  near  the  borders. 

The  entire  thickness  of  these  marls  is  unknown ;  but  it  certainly  ex- 
ceeds, in  some  places,  700  feet.  They  are,  for  the  most  part,  either  light- 
green  or  white,  and  usually  calcareous.  They  are  thinly  foliated, — a 
character  which  frequently  arises  from  the  innumerable  thin  shells,  or 
carapace-valves,  of  that  small  animal  called  Cypris.  This  animal  is  pro- 
vided with  two  small  valves,  not  unlike  those  of  a  bivalve  shell,  and 
moults  its  integuments  periodically,  which  the  conchiferous  mollusks  do 
not  This  circumstance  may  partly  explain  the  countless  myriads  of  the 
shells  of  Cypris  which  were  shed  in  the  ancient  lakes  of  Auvergne,  so  as 
to  give  rise  to  divisions  in  the  marl  as  thin  as  paper,  and  that,  too,  in 
stratified  masses  several  hundred  feet  thick.  A  more  convincing  proof  of 
the  tranquillity  and  clearness  of  the  waters,  and  of  the  slow  and  gradual 
process  by  which  the  lake  was  filled  up  with  fine  inud,  cannot  be  desired. 
But  we  may  easily  suppose  that,  while  this  fine  sediment  was  thrown 
down  in  the  deep  and  central  parts  of  the  basin,  gravel,  sand,  and  rocky 
fragments  were  hurried  into  the  lake,  and  deposited  near  the  shore,  form- 
ing the  group  described  in  the  preceding  section. 

Not  far  from  Clermont,  the  green  marls,  containing  the  Cypris  in 
abundance,  approach  to  within  a  few  yards  of  the  granite  which  forms 
the  borders  of  the  basin.  The  occurrence  of  these  marls  so  near  the 
ancient  margin  may  be  explained  by  considering  that,  at  the  bottom  of 
the  ancient  lake,  no  coarse  ingredients  were  deposited  in  spaces  inter- 
mediate between  the  points  where  rivers  and  torrents  entered,  but  finer 

Fig.  177. 


Vertical  strata  of  marl,  at  Champradelle,  near  Clermont 

A.  Granite.  B.  Space  of  60  feet,  in  which  no  section  is  seen. 

C.  Green  marl,  vertical  and  inclined.        D.  White  marl. 

mud  only  was  drifted  there  by  currents.  The  verticality  of  some  of  the 
beds  in  the  above  section  bears  testimony  to  considerable  local  disturb- 
ance subsequent  to  the  deposition  of  the  marls  ;  but  such  inclined  and 
vertical  strata  are  very  rare. 

3.  Limestone,  travertin,  oolite, — Both  the  preceding  members  of  the 
lacustrine  deposit,  the  marls  and  grits,  pass  occasionally  into  limestone. 
Sometimes  only  concretionary  nodules  abound  in  them ;  but  these,  where 
there  is  an  increase  in  the  quantity  of  calcareous  matter,  unite  into  reg- 
ular beds. 

On  each  side  of  the  basin  of  the  Limagne,  both  on  the  west  at  Gan- 
nat,  and  on  the  easjt  at  Vichy,  a  white  oolitic  limestone  is  quarried.  At 


200 


INDUSIAL  LIMESTONE. 


[On.  XV. 


Vichy,  the  oolite  resembles  our  Bath  stone  in  appearance  and  beauty ; 
and,  like  it,  is  soft  when  first  taken  from  the  quarry,  but  soon  hardens 
on  exposure  to  the  air.  At  Gannat,  the  stone  contains  land-shells  and 
bones  of  quadrupeds.  At  Chadrat,  in  the  hill  of  La  Serre,  the  limestone 
is  pisolitic,  the  small  spheroids  combining  both  the  radiated  and  concen- 
tric structure. 

Indusial  limestone. — There  is  another  remarkable  form  of  freshwater 
limestone  in  Auvergne,  called  "  indusial,"  from  the  cases,  or  inclusive,  of 
caddis-worms  (the  larvae  of  Phryganea)  \  great  heaps  of  which  have 
been  incrusted,  as  they  lay,  by  carbonate  of  lime,  and  formed  into  a  hard 
travertin.  The  rock  is  sometimes  purely  calcareous,  but  there  is  occa- 
sionally an  intermixture  of  siliceous  matter.  Several  beds  of  it  are  fre- 
quently seen,  either  in  continuous  masses,  or  in  concretionary  nodules, 
one  upon  another,  with  layers  of  marl  interposed.  The  annexed  drawing 
(fig.  178)  will  show  the  manner  in  which  one  of  these  indusial  beds  (a) 
is  laid  open  at  the  surface,  between  the  marls  (b  6),  near  the  base  of  the 
hill  of  Gergovia ;  and  affords,  at  the  same  time,  an  example  of  the  extent 
to  which  the  lacustrine  strata,  which  must  once  have  filled  a  hollow,  have 
been  denuded,  and  shaped  out  into  hills  and  valleys,  on  the  site  of  the 
ancient  lakes. 

Fi?.  178. 


Bed  of  indusial  limestone,  interstratified  with  freshwater  marl,  near  Clermont  (Kleinschrod). 

« 

We  may  often  observe  in  our  ponds  the  Phryganea  (or  Caddice-fly), 
.n  its  caterpillar  state,  covered  with  small  freshwater  shells,  which  they 
Lave  the  power  of  fixing  to  the  outside  of  their  tubular  cases,  in  order, 
probably,  to  give  them  weight  and  strength.  The  individual  figured  in 


CH.  XV,]  EOCKlSrE  PEKIOD.  201 

the  annexed  cut,  which  belongs  to  a  species  very  abundant  in  England, 
j,.   im  has  covered  its  case  with  shells  of  a  small 

Planorbis.  In  the  same  manner  a  large 
species  of  caddis-worm,  which  swarmed  in  the 
Eocene  lakes  of  Auvergne,  was  accustomed 
to  attach  to  its  dwelling  the  shells  of  a  small 
spiral  univalve  of  the  genus  Paludina.  A 
Larva  of  recent  Phryganea.*  hundred  of  these  minute  shells  are  some- 
times seen  arranged  around  one  tube,  part  of  the  central  cavity  of  which 
is  often  empty,  the  rest  being  filled  up  with  thin  concentric  layers  of 
travertin.  The  cases  have  been  thrown  together  confusedly,  and  often 
lie,  as  in  fig.  180,  at  right  angles  one  to  the  other.  When  we  consider 

Fig.  ISO. 


a.  Indusial  limestone  of  Auvergne.  5.  Fossil  Paludina  magnified. 

that  ten  or  twelve  tubes  are  packed  within  the  compass  of  a  cubic  inchj 
and  that  some  single  strata  of  this  limestone  are  6  feet  thick,  and  may 
be  traced  over  a  considerable  area,  we  may  form  some  idea  of  the  count- 
less number  of  insects  and  mollusca  which  contributed  their  integuments 
and  shells  to  compose  this  singularly  constructed  rock.  It  is  unnecessa- 
ry to  suppose  that  the  Phryganece  lived  on  the  spots  where  their  cases 
are  now  found ;  they  may  have  multiplied  in  the  shallows  near  the 
margin  of  the  lake,  or  in  the  streams  by  which  it  was  fed,  and  their 
cases  may  have  been  drifted  by  a  current  far  into  the  deep  water. 

In  the  summer  of  1837,  when  examining,  in  company  with  Dr.  Beck, 
a  small  lake  near  Copenhagen,  I  had  an  opportunity  of  witnessing  a 
beautiful  exemplification  of  the  manner  in  which  the  tubular  cases  of 
Auvergne  were  probably  accumulated.  This  lake,  called  the  Fuure-Soe, 
occurring  in  the  interior  of  Seeland,  is  about  twenty  English  miles  in 
circumference,  and  in  some  parts  200  feet  in  depth.  Kound  the  shallow 
borders  an  abundant  crop  of  reeds  and  rushes  may  be  observed,  covered 
with  the  indusia  of  the  Phryganea  grandis  and  other  species,  to  which 
shells  are  attached.  The  plants  which  support  them  are  the  bullrush. 
Scirpus  lacustris,  and  common  reed,  Arundo  phragmites,  but  chiefly  the 
former.  In  summer,  especially  in  the  month  of  June,  a  violent  gust  of 
wind  sometimes  causes  a  current  by  which  these  plants  are  torn  up  by 
the  roots,  washed  away,  and  floated  off  in  long  bands,  more  than  a  mile 
in  length,  into  deep  water.  The  Cypris  swarms  in  the  same  lake ;  and 
calcareous  springs  alone  are  wanting  to  form  extensive  beds  of  indusial 
limestone,  like  those  of  Auvergne. 

*  I  believe  that  the  British  specimen  here  figured  is  P.  rhombica,  Linn. 


202  LACUSTKINE  STKATA — AUVERGNE.  [Cn.  XV 

4.  Gypseous  marls. — More  than  50  feet  of  thinly  laminated  gypseous 
marls,  exactly  resembling  those  in  the  hill  of  Montmartre,  at  Paris,  are 
worked  for  gypsum  at  St.  Romain,  on  the  right  bank  of  the  Allier.  They 
rest  on  a  series  of  green  cypridiferous  marls  which  alternate  with  grit,  the 
united  thickness  of  this  inferior  group  being  seen,  in  a  vertical  section  OB 
the  banks  of  the  river,  to  exceed  250  feet. 

General  arrangement,  origin,  and  age  of  the  freshwater  formations 
of  Auvergne. — The  relations  of  the  different  groups  above  described  can- 
not be  learnt  by  the  study  of  any  one  section ;  and  the  geologist  who 
sets  out  with  the  expectation  of  rinding  a  fixed  order  of  succession  may 
perhaps  complain  that  the  different  parts  of  the  basin  give  contradictory 
results.  The  arenaceous  division,  the  marls,  and  the  limestone,  may  aL 
be  seen  in  some  places  to  alternate  with  each  other  ;  yet  it  can  by  no 
means  be  affirmed  that  there  is  no  order  of  arrangement.  The  sands, 
sandstone,  and  conglomerate  constitute  in  general  a  littoral  group  ;  the 
foliated  white  and  green  marls,  a  contemporaneous  central  deposit ;  and 
the  limestone  is  for  the  most  part  subordinate  to  the  newer  portions  of 
both.  The  uppermost  marls  and  sands  are  more  calcareous  than  the 
lower ;  and  we  never  meet  with  calcareous  rocks  covered  by  a  consider- 
able thickness  of  quartzose  sand  or  green  marl.  From  the  resemblance 
of  the  limestones  to  the  Italian  travertins,  we  may  conclude  that  they 
were  derived  from  the  waters  of  mineral  springs, — such  springs  as  even 
now  exist  in  Auvergne,  and  which  may  be  seen  rising  up  through  the 
granite,  and  precipitating  travertin.  They  are  sometimes  thermal,  but 
this  character  is  by  no  means  constant. 

It  seems  that,  when  the  ancient  lake  of  the  Limagne  first  began  to  be 
filled  with  sediment,  no  volcanic  action  had  yet  produced  lava  and  scoriae 
on  any  part  of  the  surface  of  Auvergne.  No  pebbles,  therefore,  of  lava 
were  transported  into  the  lake, — no  fragments  of  volcanic  rocks  im- 
bedded in  the  conglomerate.  But  at  a  later  period,  when  a  considerable 
thickness  of  sandstone  and  marl  had  accumulated,  eruptions  broke  out, 
and  lava  and  tuff  were  deposited,  at  some  spots,  alternately  with  the 
lacustrine  strata.  It  is  not  improbable  that  cold  and  thermal  springs, 
holding  different  mineral  ingredients  in  solution,  became  more  numerous 
during  the  successive  convulsions  attending  this  development  of  volcanic 
agency,  and  thus  deposits  of  carbonate  and  sulphate  of  lime,  silex,  and 
other  minerals  were  produced.  Hence  these  minerals  predominate  in 
the  uppermost  strata.  The  subterranean  movements  may  then  have 
continued,  until  they  altered  the  relative  levels  of  the  country,  and  caused 
the  waters  of  the  lakes  to  be  drained  off,  and  the  farther  accumulation 
of  regular  freshwater  strata  to  cease. 

We  may  easily  conceive  a  similar  series  of  events  to  give  rise  to  anal- 
ogous results  in  any  modern  basin,  such  as  that  of  Lake  Superior,  for 
example,  where  numerous  rivers  and  torrents  are  carrying  down  the 
detritus  of  a  chain  of  mountains  into  the  lake.  The  transported  mate- 
rials must  be  arranged  according  to  their  size  and  weight,  the  coarser 
near  the  shore,  the  finer  at  a  greater  distance  from  land ;  but  in  the 


Ca  XV.]  UPPER  EOCENE  STRATA.  203 

gravelly  and  sandy  beds  of  Lake  Superior  no  pebbles  of  modern  volcanic 
rocks  can  be  included,  since  there  are  none  of  these  at  present  in  the 
district.  If  igneous  action  should  break  out  in  that  country,  and  pro- 
duce lava,  scoriae,  and  thermal  springs,  the  deposition  of  gravel,  sand, 
and  marl  might  still  continue  as  before ;  but,  in  addition,  there  would 
then  be  an  intermixture  of  volcanic  gravel  and  tuff,  and  of  rocks  precip- 
itated from  the  waters  of  mineral  springs. 

Although  the  freshwater  strata  of  the  Limagne  approach  generally  to 
a  horizontal  position,  the  proofs  of  local  disturbance  are  sufficiently 
numerous  and  violent  to  allow  us  to  suppose  great  changes  of  level  since 
the  lacustrine  period.  We  are  unable  to  assign  a  northern  barrier  to  the 
ancient  lake,  although  we  can  still  trace  its  limits  to  the  east,  west,  and 
south,  where  they  were  formed  of  bold  granite  eminences.  Nor  need 
we  be  surprised  at  our  inability  to  restore  entirely  the  physical  geography 
of  the  country  after  so  great  a  series  of  volcanic  eruptions ;  for  it  is  by 
no  means  improbable  that  one  part  of  it,  the  southern,  for  example,  may 
have  been  moved  upwards  bodily,  while  others  remained  at  rest,  or  even 
suffered  a  movement  of  depression. 

Whether  all  the  freshwater  formations  of  the  Limagne  d' Auvergne 
belong  to  one  period,  I  cannot  pretend  to  decide,  as  large  masses  both  of 
the  arenaceous  and  marly  groups  are  often  devoid  of  fossils.  Some  of 
the  oldest  or  lowest  sands  and  marls  may  very  probably  be  of  Middle 
Eocene  date.  Much  light  has  been  thrown  on  the  mammiferous  fauna  by 
the  labors  of  MM.  Bravard  and  Croizet,  and  by  those  of  M.  Pomel.  The 
last-mentioned  naturalist  has  pointed  out  the  specific  distinction  of  all,  or 
nearly  all,  the  species  of  mammalia  from  those  of  the  gypseous  series  near 
Paris,  although  many  of  the  forms  are  analogous  to  those  of  Eocene 
quadrupeds.  The  Cainotkerium,  for  example,  is  not  far  removed  from 
the  Anoplotherium,  and  is,  according  to  Waterhouse,  the  same  as  the 
genus  Microtherium  of  the  Germans.  There  are  two  species  of  marsupial 
animals  allied  to  Didelphys,  a  genus  also  found  in  the  Paris  gypsum,  and 
several  forms  of  ruminants  of  extinct  genera,  such  as  Amphitragulas  elegans 
of  Pomel,  which  has  been  identified  with  a  Rhenish  species  from  Weisse- 
nau  near  Mayence,  called  by  Kaup  Dorcatkerium  nanum  ;  other  associ- 
ated fossils,  e.  g.,  Microtherium  Reuggeri,  and  a  small  rodent,  Titanomys, 
are  also  specifically  the  same  with  mammalia  of  the  Mayence  basin.  The 
Hycenodon,  a  remarkable  carnivorous  genus,  is  represented  by  more  than 
one  species,  and  the  oldest  representative  of  the  genus  Machairodus  has 
been  discovered  in  these  beds  in  Auvergne.  The  first  of  these,  Hycenodon, 
also  occurs  in  the  English  Middle-Eocene  marls  of  Hordwell  cliff,  Hamp- 
shire, considerably  below  the  level  of  the  Bembridge  limestone,  with 
Paleotheria.  Upon  the  whole  it  is  clear  that  a  large  portion  of  the 
Limagne  rocks  have  been  correctly  referred  by  French  geologists  to  their 
Middle  Tertiary,  and  to  that  part  of  it  which  is  called  Upper  Eocene 
in  this  work. 

Cantal — A  freshwater  formation,  of  about  the  same  age  and  very 
analogous  to  that  of  Auvergne,  is  situated  in  the  department  of  Haute 


204  UPPER  EOCENE  STRATA — CANTAL.  [dr.  XV. 

Loire,  near  the  town  of  Le  Puy,  in  Velay ;  and  another  occurs  neat 
Aurillac,  in  Cantal.  The  leading  feature  of  the  formation  last  mentioned, 
as  distinguished  from  those  of  Auvergne  and  Velay,  is  the  immense 
abundance  of  silex  associated  with  calcareous  marls  and  limestone. 

The  whole  series  may  be  separated  into  two  divisions ;  the  lower,  com- 
posed of  gravel,  sand,  and  clay,  such  as  might  have  been  derived  from 
the  wearing  down  and  decomposition  of  the  granitic  schists  of  the 
surrounding  country  ;  the  upper  system,  consisting  of  siliceous  and  calca- 
reous marls,  contains  subordinately  gypsum,  silex,  and  limestone. 

The  resemblance  of  the  freshwater  limestone  of  the  Cantal,  and  its 
accompanying  flint,  to  the  upper  chalk  of  England,  is  very  instructive, 
and  well  calculated  to  put  the  student  upon  his  guard  against  rely- 
ing too  implicitly  on  miperal  character  alone  as  a  safe  criterion  of  rela- 
tive age. 

When  we  approach  Aurillac  from  the  west,  we  pass  over  great  heathy 
plains,  where  the  sterile  mica-schist  is  barely  covered  with  vegetation. 
Near  Ytrac,  and  between  La-Capelle  and  Viscamp,  the  surface  is  strewed 
over  with  loose  broken  flints,  some  of  them  black  in  the  interior,  but 
with  a  white  external  coating ;  others  stained  with  tints  of  yellow  and 
red,  and  in  appearance  precisely  like  the  flint  gravel  of  our  chalk  districts. 
When  heaps  of  this  gravel  have  thus  announced  our  approach  to  a  new 
formation,  we  arrive  at  length  at  the  escarpment  of  the  lacustrine  beds. 
At  the  bottom  of  the  hill  which  rises  before  us,  we  see  strata  of  clay 
and  sand,  resting  on  mica-schist ;  and  above,  in  the  quarries  of  Belbet, 
Leybros,  and  Bruel,  a  white  limestone,  in  horizontal  strata,  the  surface  of 
which  has  been  hollowed  out  into  irregular  furrows,  since  filled  up  with 
broken  flint,  marl,  and  dark  vegetable  mould.  In  these  cavities  we  recog- 
nize an  exact  counterpart  to  those  which  are  so  numerous  on  the  fur- 
rowed surface  of  our  own  white  chalk.  Advancing  from  these  quarries 
along  a  road  made  of  the  white  limestone,  which  reflects  as  glaring  a  light 
in  the  sun  as  do  our  roads  composed  of  chalk,  we  reach,  at  length,  in 
the  neighborhood  of  Aurillac,  hills  of  limestone  and  calcareous  marl,  in 
horizontal  strata,  separated  in  some  places  by  regular  layers  of  flint  in 
nodules,  the  coating  of  each  nodule  being  of  an  opaque  white  color,  like 
the  exterior  of  the  flinty  nodules  of  our  chalk. 

The  abundant  supply  both  of  siliceous,  calcareous,  and  gypseous  mat- 
ter, which  the  ancient  lakes  of  France  received,  may  have  been  connected 
with  the  subterranean  volcanic  agency  of  which  those  regions  were  so 
long  the  theatre,  and  which  may  have  impregnated  the  springs  with  min- 
eral matter,  even  before  the  great  outbreak  of  lava.  It  is  well  known  that 
the  hot  springs  of  Iceland,  and  many  other  countries,  contain  silex  in  solu- 
tion ;  and  it  has  been  lately  affirmed,  that  steam  at  a  high  temperature  is 
capable  of  dissolving  quartzose  rocks  without  the  aid  of  any  alkaline  or 
other  flux.*  Warm  wa.ter  charged  with  siliceous  matter  would  immedi- 
ately part  with  a  portion  of  its  silex,  if  its  temperature  was  lowered  by 
mixing  with  the  cooler  waters  of  a  lake. 

*  See  Proceedings  of  Royal  Soc.,  No.  44,  p.  288. 


Cir.  XV.]  SLOWNESS  OF  DEPOSITION.  205 

A  hasty  observation  of  the  white  limestone  and  flint  of  Aurillac  might 
convey  the  idea  that  the  rock  was  of  the  same  age  as  the  white  chalk  of 
Europe ;  but  when  we  turn  from  the  mineral  aspect  and  composition  to 
the  organic  remains,  we  find  in  the  flints  of  the  Cantal  seed-vessels  of  the 
freshwater  Chara,  instead  of  the  marine  zoophytes  so  abundant  in  chalk 
flints ;  and  in  the  limestone  we  meet  with  shells  of  Limnea,  Planorbis, 
and  other  lacustrine  genera. 

Proofs  of  gradual  deposition. — Some  sections  of  the  foliated  marls  in 
the  valley  of  the  Cer,  near  Aurillac,  attest,  in  the  most  unequivocal  man- 
ner, the  extreme  slowness  with  which  the  materials  of  the  lacustrine  series 
were  amassed.  In  the  hill  of  Barrat,  for  example,  we  find  an  assemblage 
of  calcareous  and  siliceous  marls ;  in  which,  for  a  depth  of  at  least  60 
feet,  the  layers  are  so  thin,  that  thirty  are  sometimes  contained  in  the 
thickness  of  an  inch ;  and  when  they  are  separated,  we  see  preserved  in 
every  one  of  them  the  flattened  stems  of  Charce,  or  other  plants,  or  some- 
times myriads  of  small  Paludince  and  other  freshwater  shells.  These 
minute  foliations  of  the  marl  resemble  precisely  some  of  the  recent  lamina- 
ted beds  of  the  Scotch  marl  lakes,  and  may  be  compared  to  the  pages  of 
a  book,  each  containing  a  history  of  a  certain  period  of  the  past.  The 
different  layers  may  be  grouped  together  in  beds  from  a  foot  to  a  foot 
and  a  half  in  thickness,  which  are  distinguished  by  differences  of  composi- 
tion and  color,  the  tints  being  white,  green,  and  brown.  Occasionally 
there  is  a  parting  layer  of  pure  flint,  or  of  black  carbonaceous  vegetable 
matter,  about  an  inch  thick,  or  of  white  pulverulent  marl.  We  find  sev- 
eral hills  in  the  neighborhood  of  Aurillac  composed  of  such  materials,  for 
the  height  of  more  than  200  feet  from  their  base,  the  whole  sometimes 
covered  by  rocky  currents  of  trachytic  or  basaltic  lava.* 

Thus  wonderfully  minute  are  the  separate  parts  of  which  some  of  the 
most  massive  geological  monuments  are  made  up  !  When  we  desire  to 
classify,  it  is  necessary  to  contemplate  entire  groups  of  strata  in  the  aggre- 
gate ;  but  if  we  wish  to  understand  the  mode  of  their  formation,  and  to 
explain  their  origin,  we  must  think  only  of  the  minute  subdivisions  of 
which  each  mass  is  composed.  We  must  bear  in  mind  how  many  thin 
leaf-like  seams  of  matter,  each  containing  the  remains  of  myriads  of  tes- 
tacea  and  plants,  frequently  enter  into  the  composition  of  a  single  stratum, 
and  how  vast  a  succession  of  these  strata  unite  to  form  a  single  group ! 
We  must  remember,  also,  that  piles  of  volcanic  matter,  like  the  Plomb 
du  Cantal,  which  rises  in  the  immediate  neighborhood  of  Aurillac,  are 
themselves  equally  the  result  of  successive  accumulation,  consisting  of 
reiterated  sheets  of  lava,  showers  of  scorise,  and  ejected  fragments  of 
rock. — Lastly,  we  must  not  forget  that  continents  and  mountain-chains, 
colossal  as  are  their  dimensions,  are  nothing  more  than  an  assemblage  of 
many  such  igneous  and  aqueous  groups,  formed  in  succession  during  an 
indefinite  lapse  of  ages,  and  superimposed  upon  each  other. 

Bourdeaux,  Aix,  &c. — The  Upper  Eocene  Strata  in  the  Bourdeaux 

*  Lyell  and  Murchison,  sur  les  Dep&ts  Lacustres  Tertiaires  du  Cantal,  Ac.  Ana 
des  ScL  Nat.  Oct.  1829. 


206         UPPER  EOCENE  OF  NEBRASKA,  U.  S.     [On.  XV. 

basin  are  represented,  according  to  M.  Raulin,  by  the  Falun  de  Leognan, 
and  the  underlying  limestone  of  St.  Macaire.  By  many,  however,  the 
upper  of  these,  or  the  Leognan  beds,  are  considered  to  be  no  older  than 
the  faluns  of  Touraine.  The  freshwater  strata  of  Aix-en- Provence  are 
probably  Upper  Eocene  ;  also  the  tertiary  rocks  of  Malta,  Crete,  Cerigo, 
and  those  of  many  parts  of  Greece  and  other  countries  bordering  the 
Mediterranean . 

Nebraska,  United  States. — In  the  territory  of  Nebraska,  on  the  Upper 
Missouri,  near  the  Platte  River,  lat.  42°  N.,  a  tertiary  formation  occurs, 
consisting  of  white  limestone,  marls,  and  siliceous  clay,  described  by  Dr. 
D.  Dale  Owen,*  in  which  many  bones  of  extinct  quadrupeds,  and  of 
chelonians  of  land  or  freshwater  forms,  are  met  with.  Among  these, 
Dr.  Leidy  recognizes  a  gigantic  Palceotherium,  larger  than  any  of  the 
Parisian  species  ;  several  species  of  the  genus  Orcodon,  Leidy,  uniting  the 
characters  of  pachyderms  and  ruminants ;  Eucrotaphus,  another  new 
genus  of  the  same  mixed  character ;  two  species  of  rhinoceros  of  the 
sub-genus  Acerotherium,  an  Upper  Eocene  form  of  Europe  before  men- 
tioned ;  two  of  Archceotherium,  a  pachyderm  allied  to  Chceropotamus 
and  Hyracotherium  ;  also  Poebrotherium,  an  extinct  ruminant  allied  to 
Dorcatherium,  Kaup ;  also  Agriochoegus  of  Leidy,  a  ruminant  allied 
to  Merycopotamus  of  Falconer  and  Cautley ;  and,  lastly,  a  large  car- 
nivorous animal  of  the  genus  Machairodus,  the  most  ancient  example 
of  which  in  Europe  occurs  in  the  Upper  Eocene  beds  of  Auvergne. 
The  turtles  are  referred  to  the  genus  Testudo,  but  have  some  affinity 
to  Emys.  On  the  whole,  this  formation  has,  I  believe,  been  correctly 
referred  by  American  writers  to  the  Eocene  period,  in  conformity  with 
the  classification  adopted  by  me,  but  would,  I  conceive,  be  called  Lower 
Miocene  by  those  who  apply  that  term  to  all  strata  newer  than  the 
Paris  gypsum. 

*  David  Dale  Owen,  Geol  Survey  of  Wisconsin,  &c. ;  Philad.  1852. 


CH.  XVI.1 


MIDDLE   EOCENE   FORMATIONS. 


207 


CHAPTER   XVI. 


MIDDLE    AND    LOWER    EOCENE    FORMATIONS. 

Middle  Eocene  strata  of  England — Fluvio-marine  series  in  the  Isle  of  Wight  and 
Hampshire — Successive  groups  of  Eocene  Mammalia — Fossils  of  Barton  Clay — 
Shells,  mummulites,  fishes,  and  reptiles  of  the  Bagshot  and  Bracklesham  beds 
— Lower  Eocene  strata  of  England — Fossil  plants  and  shells  of  the  London 
Clay  proper — Strata  of  Kyson  in  Suffolk — Fossil  monkey  and  opossum — Plastic 
clays  and  sands — Thanet  sands — Middle  Eocene  formations  of  France — Gyp- 
seous series  of  Montmartre  and  extinct  quadrupeds — Calcaire  grossier — Milio- 
lites — Lower  Eocene  in  France — Nummulitic  formations  of  Europe  and  Asia — 
Their  wide  extent ;  referable  to  the  Middle  Eocene  period — Eocene  strata  in 
the  United  States — Section  at  Claiborne,  Alabama — Colossal  cetacean — Orbitoid 
limestone — Burr-stone. 

THE  strata  next  in  order  in  the  descending  series  are  those  which  I 
term  Middle  Eocene.  In  the  accompanying  map,  the  position  of  several 
Eocene  areas  is  pointed  out,  such  as  the  basin  of  the  Thames,  part  of 

Fig.  181. 
Map  of  the  principal  tertiary  basins  of  the  Eocene  period. 


IHypogene  rocks  and  strata 
older  than  the  Devonian 
or  Old  Eed  series. 


Eocene  formations. 


N.  B.  The  space  left  blank  is  occupied  by  secondary  formations  from  the  Devonian  or  old  red 
sandstone  to  the  chalk  inclusive. 

Hampshire,  part  of  the  Netherlands,  and  the  country  round  Paris.  The 
three  last-mentioned  areas  contain  some  marine  and  freshwater  formations, 
which  have  been  already  spoken  of  as  Upper  Eocene,  but  their  superficial 
extent  in  this  part  of  Europe  is  insignificant. 

ENGLISH   MIDDLE   EOCENE   FORMATIONS. 

The  following  table  will  show  the  order  of  succession  of  the  strata  found 
in  the  Tertiary  areas,  commonly  called  the  London  and  Hampshire 
basins.  (See  also  Table,  p.  104,  et  seq.) 


203  ENGLISH  MIDDLE  EOCENE   FORMATIONS.         [On.  XVI. 

UPPER  EOCENE. 

Thickness. 

A.  Hempstead  beds,  Isle  of  Wight,  see  above,  p.  192        -        -     170  feet. 

MIDDLE   EOCENE. 

B.  1.  Bembridge  Series,— North  coast  of  Isle  of  Wight         -        -  120 

B.  2.  Osborne  or  St.  Helen's  Series, — ibid. 100 

B.  8.  Headon  Series,— Isle  of  Wight,  and  Hordwell  Cliff,  Hants  -  170 
B.  4.  Headon  Hill  sands  and  Barton  Clay, — Isle  of  Wight,  and 

Barton  Cliff,  Hants 300 

B.  5.  Bagshot  and  Bracklesham  Sands  and  Clays, — London  and 

Hants  basins 700 

LOWER    EOCENE. 

C.  1.  London  Clay  proper  and  Bognor  beds, — London  and  Hants 

basins 360  to  600 

C.  2.  Plastic  and  Mottled  Clays  and  Sands  (Woolwich  and  Reading 

series), — London  and  Hants  basins 100 

C.  3.  Thanet  Sands, — Reculvers,  Kent,  and  Eastern  part  of  London 

basin 90 

The  true  place  of  the  Bagshot  sands,  B.  5  in  the  above  series,  and  of 
the  Thanet  sands,  C.  3,  was  first  accurately  ascertained  by  Mr.  Prestwich 
in  1847  and  1852.  The  true  relative  position  of  the  Hempstead  beds,  A, 
of  the  Bembridge,  B.  1,  and  of  the  Osbome  or  St.  Helen's  series,  B.  2, 
were  not  made  out  in  a  satisfactory  manner  till  Professor  Forbes  studied 
them  in  detail  in  1852. 

Bembridge  series,  B.  1. — These  beds  are  above  100  feet  thick,  and,  as 
before  stated  (p.  187),  pass  upwards  into  the  Hempstead  beds,  with  which 
they  are  conformable,  near  Yarmouth,  in  the  Isle  of  Wight.  They  con- 
sist of  marls,  clays,  and  limestones  of  freshwater,  brackish,  and  marine 
01  igin.  Some  of  the  most  abundant  shells,  as  Cyrena  semistriata  var., 
and  Paludina,  lenta  (fig.  175,  p.  193),  are  common  to  this  and  to  the 
overlying  Hempstead  series.  The  following  are  the  subdivisions  described 
by  Professor  Forbes : 

a.  Upper  marls,  distinguished  by  the  abundance  of  Melania  turritissima,  Forbes 
(fig.  182). 

Fig.  182.  Fig.  183. 


Melania  turritissima,  Forbes.  Fragment  of  Carapace  of  Triony®. 

Bembridge.  Bembridge  Beds,  Isle  of  Wight. 

b.  Lower  marl,  characterized  by  Cerithium  mutabile,  Cyrena  pulchra,  &c.,  and  by 

the  remains  of  Trionyx  (see  fig.  183). 

c.  Green  marls,  often  abounding  in  a  peculiar  species  of  oyster,  and  accompanied 

by  Cerithia,  Mytili,  an  Area,  a  Nucula,  (fee. 

d.  Bembridge  limestones,  compact  cream-colored  limestones  alternating  with 


CH.  XVI]      FLUVIO-MAKIXE   SERIES  IN  ISLE   OF  WIGHT. 


209 


shales  and  marls,  in  all  of  which  land-shells  are  common,  especially  at  Sconce, 
near  Yarmouth,  and  have  been  described  by  Mr.  Edwards.  The  Bulimus  ellip- 
ticus  (fig.  184),  and  Helix  occlusa  (fig.  185),  are  among  its  best-known  laud- 


Fig.  184. 


Fig.  185. 


Fig.  186. 


ulimvA  ellipticus,  Sow.        Helix  occlusa,  Edwards, 
Bembridge  Limestone,  Sconce  Limestone, 

half  natural  size.  Isle  of  Wight 


Paludina  orMcularis,  Bembridge. 


shells.     Paludina  orbicularis  (fig.  186)  is  also  of  frequent  occurrence.     One  of 
the  bands  is  filled  with  a  little  globular  Paludina.     Among  the  freshwater 


Fig.  1ST. 


Fig.  188. 


Fig.  189. 


Planorbis  d iscus,  Edwards.  Bem- 
bridge. 


Lymnea  longiscata,  Brard. 


Chara  tuberculata. 
Bembridse  Lime- 
stone, L  of  Wight. 

pulmonifera,  Lymnea  longiscata  (fig.  188)  and  Planorbis  discus  (fig.  187)  are 
e  most  generally  distributed :  the  latter  represents  or  takes  the  place  of  the 
Planorbis  euomphalus  (see  fig.  192),  of  the  more  ancient  Headon  series.     Chara 
tuberculata  (fig.  189),  is  the  characteristic  Bembridge  gyrogonite. 

From  this  formation  on  the  shores  of  Whitecliff  Bay,  Dr.  Mantell  ob- 
tained a  fine  specimen  of  a  fan  palm,  Flabellaria  Lamanonis,  Brong.,  a 
plant  first  obtained  from  beds  of  corresponding  age  in  the  suburbs  of 
Paris.  The  well-known  building-stone  of  Binstead,  near  Ryde,  a  lime- 
stone with  numerous  hollows  caused  by  Cyrmce  which  have  disappeared 
and  left  the  moulds  of  their  shells,  belongs  to  this  subdivision  of 
the  Bembridge  series.  In  the  same  Binstead  stone  Mr.  Pratt  and 
the  Rev.  Darwin  Fox  first  discovered  the  remains  of  mammalia  char- 
acteristic of  the  gypseous  series  of  Paris,  as  Palceotherium  magnum 

14 


210  FLUVIO-MARINE  SERIES  IN  ISLE   OF  WIGHT.       [Cn.  XVJ. 


(fig.   191),  P.  medium,  P.  minus,  P.  mimimum,  P.  Fig.  190. 

curium,  P.  crassum ;  also  Anoplotherium  commune 

(fig.  190),  A.,  secundarium,  Dichobune  cervinum,  and 

Cheer opotamus  Cuvieri.     The  genus  Paleothere,  above 

alluded  to,  resembled  the  living  tapir  in  the  form  of 

the  head,  and  in  having  a  short  proboscis,  but  its  molar 

teeth  were  more  like  those  of  the  rhinoceros  (see  fig. 

1 90).     Paleotherium  magnum  was  of  the  size  of  a 

horse,  three  or  four  feet  high.     The  annexed  woodcut 

(fig.  191)  is-  one  of  the  restorations  whieh  Cuvier  at-  Blnstead' Isle  of  Wight 

tempted  of  the  outline  of  the  living  animal,  derived  from  the  study  of  the 

Fig.  191. 


Lower  Molar  tooth, 

nat.  size. 

Anoplotherium  com,' 
mune. 


Paleotherium  magnum,  Cuvier. 

entire  skeleton.  As  the  vertical  range  of  particular  species  of  quadrupeds, 
so  far  as  our  knowledge  extends,  is  far  more  limited  than  that  of  the  tes- 
tacea ;  the  occurrence  of  so  many  species  at  Binstead,  agreeing  with 
fossils  of  the  Paris  gypsum,  strengthens  the  evidence  derived  from  shells 
and  plants  of  the  synchronism  of  the  two  formations. 

Osborne  or  St.  Helen's  series,  B.  2. — This  group  is  of  fresh  and  brack- 
ish-water origin,  and  very  variable  in  mineral  character  and  thickness. 
Near  Hyde,  it  supplies  a  freestone  much  used  for  building,  and  called  by 
Professor  Forbes  the  Nettlestone  grit.  In  one  part  ripple-marked  flag- 
stones occur,  and  rocks  with  fucoidal  markings.  The  Osborne  beds  are 
distinguished  by  peculiar  species  of  Paludina,  Melania,  and  Melanopsis, 
as  also  of  Cypris  and  the  seeds  of  Cham. 

Headon  series,  B.  3. — These  beds  are  seen  both  at  the  east  and  west 
extremities  of  the  Isle  of  Wight,  and  also  in  Hordwell  Cliffs,  Hants. 
Everywhere  Planorbis  euomphalus  (fig.  192)  characterizes  the  freshwater 
deposits,  just  as  the  allied  form,  P.  discus  (fig.  187)  does  the  Bembridge 
limestone.  The  brackish-water  beds  contain  Patomomya  plana,  Cerithium 
mutabile,  and  C.  cinctum  (fig.  44,  p.  30),  and  the  marine  beds  Venus 
(or  Cytherea)  incrassata,  a  species  common  to  the  Limburg  beds  and 
Ores  de  Fontainebleau,  or  the  Upper  Eocene  series.  The  prevalence  of 


CH.  XVI.] 


SHELL   OF   THE   HEADON   SERIES. 


211 


salt-water  remains  is  most  conspicuous  in  some  of  the  central  parts  of  the 
formation.     Mr.  T.  Webster,  in  his  able  memoirs  on  the  Isle  of  Wight, 


Fig.  192. 


Fig.  wa 


Planorbis  eiuymphalui,  Sow. 
Headon  HilL    \  diam. 


Helix  Idbyrinthica,  Say.    Headon  Hill,  Isle  of  Wight ; 
and  Hordwell  Cliff,  Hants— also  recent. 


first  separated  the  wnole  into  a  lower  freshwater,  an  upper  marine,  and 
an  upper  freshwater  division. 

Among  the  shells  which  are  widely  distributed  through  the  Headon 
series  are  Neritina  concava  (fig.  194),  Lymnea  caudata  (fig.  195),  and 
Ceritkium  concavum  (fig.  196).  Helix  labyrinthica,  Say  (fig.  193),  a 


Fig.  194. 


Fig.  195. 


Fig.  196. 


Neritina  concava. 
Headon  Series. 


Lymnea  caudata. 
Headon  Beds. 


Cerithium  concavum. 
Headon  Series. 


land-shell  now  inhabiting  the  United  States,  was  discovered  in  this  series 
by  Mr.  Wood  in  Hordwell  Cliff.  It  is  also  met  with  in  Headon  Hill,  in 
the  same  beds.  At  Sconce,  in  the  Isle  of  Wight,  it  occurs  in  the  newer 
Bembridge  series,  and  affords  a  rare  example  of  an  Eocene  fossil  of  a  spe- 
cies still  living,  though,  as  usual  in  such  cases,  having  no  local  connection 
with  the  actual  geographical  range  of  the  species. 

The  lower  and  middle  portion  of  the  Headon  series  is  also  met  with  in 
Hordwell  Cliff  (or  Hordle,  as  it  is  often  spelt),  near  Lymington,  Hants, 
where  the  organic  remains  have  been  studied  by  Mr.  Searles  Wood,  Dr. 
Wright,  and  the  Marchioness  of  Hastings.  To  the  latter  we  are  indebted 
for  a  detailed  section  of  the  beds,*  as  well  as  for  the  discovery  of  a  variety 
of  new  species  of  fossil  mammalia,  chelonians,  and  fish  ;  also  for  first  call- 
ing attention  to  the  important  fact  that  these  vertebrata  differ  specifically 
from  those  of  the  Bembridge  beds.  Among  the  abundant  shells  of  Hord- 
well are  Paludina  lenta  and  various  species  of  Lymneus,  Planorbis, 
Melania,  Cyclas,  and  Unio,  Potomomya,  Dreissena,  &c. 

*  Bulletin,  Soc.  Geol.  de  France,  1852,  p.  191. 


212  FLUVIO-MAKINE  SEEIES  IN  HAMPSHIRE.         [On.  XVI. 

Among  the  chelonians  we  find  a  species  ©f  Emys,  and  no  less  than  six 
species  of  Trionyx ;  among  the  saurians  an  alligator  and  a  crocodile ; 
among  the  ophidians  two  species  of  land-snakes  (Paleryx,  Owen) ;  and 
among  the  fish  Sir  P.  Egerton  and  Mr.  Wood  have  found  the  jaws,  teeth, 
and  hard  shining  scales  of  the  genus  Lepidosteus  or  bony  pike  of  the 
American  rivers.  This  same  genus  of  freshwater  ganoids  has  also  been 
met  with  in  the  Hempstead  beds  of  the  Isle  of  Wight.  The  bones  of 
several  birds  have  been  obtained  from  Hordwell,  and  the  remains  of  quad- 
rupeds. The  latter  belong  to  the  genera  Paloplotherium  of  Owen,  Ano- 
plotherium,  Anthracotherium,  Dichodon  of  Owen  (a  new  genus  discovered 
by  Mr.  A.  H.  Falconer),  Dichobunc,  Spalacodon,  and  Hycenodon.  The 
latter  offers,  I  believe,  the  oldest  known  example  of  a  true  carnivorous 
mammal  in  the  series  of  British  fossils,  although  I  attach  very  little  the- 
oretical importance  to  the  fact,  because  herbivorous  species  are  those  most 
easily  met  with  in  a  fossil  state  in  all  save  cavern  deposits.  In  another 
point  of  view,  however,  this  fauna  deserves  notice.  Its  geological  position 
is  considerably  lower  than  that  of  the  Bembridge  or  Montmartre  beds, 
from  which  it  differs  almost  as  much  in  species  as  it  does  from  the 
still  more  ancient  fauna  of  the  Lower  Eocene  beds  to  be  mentioned 
in  the  sequel.  It  therefore  teaches  us  what  a  grand  succession  of  distinct 
assemblages  of  mammalia  flourished  on  the  earth  during  the  Eocene 
period. 

Many  of  the  marine  shells  of  the  brackish-water  beds  of  the  above 
series,  both  in  the  Isle  of  Wight  and  Hordwell  Cliff,  are  common  to  the 
underlying  Barton  clay ;  and,  on  the  other  hand,  there  are  some  fresh- 
water shells,  such  as  Cyrena  obovata,  which  are  common  to  the  Bem- 
bridge beds,  notwithstanding  the  intervention  of  the  St.  Helen's  series. 
The  white  and  green  marls  of  the  Headon  series,  and  some  of  the  accom- 
panying limestones,  often  resemble  the  Eocene  strata  of  France  in  mineral 
character  and  color  in  so  striking  a  manner,  as  to  suggest  the  idea  that 
the  sediment  was  derived  from  the  same  region  or  produced  contempo- 
raneously under  very  similar  geographical  circumstances. 

Both  in  Hordwell  Cliff  and  in  the  Isle  of  Wight,  the  Headon  beds  rest 
on  white  sands,  the  upper  member  of  the  Barton  series,  B.  4,  next  to  be 
mentioned. 

Headon  Hill  sands  and  Barton  clay,  B.  4  (Table,  p.  208). — In  one  of 
the  upper  and  sandy  beds  of  this  formation  Dr.  Wright 
found  Chama  squamosa  in  great  plenty.  The  same  sands  Fi&- 197- 
contain  impressions  of  many  marine  shells  (especially  in 
Whitecliff  Bay)  common  to  the  uppeY  Bagshot  sands 
afterwards  to  be  described.  The  underlying  Barton  clay 
has  yielded  about  209  marine  shells,  more  than  half  of 
them,  according  to  Mr.  Prestwich,  peculiar;  and  only 
eleven  common  to  the  London  clay  proper  (C.  1,  p.  208), 
being  in  the  proportion  of  only  5  per  cent.  On  the  other 
hand,  70  of  them  agree  with  the  shells  of  the  calcaire 
grossier  of  France.  It  is  nearly  a  century  since  Brander  published,  in 


CH  XVI.] 


FOSSILS  OF   THE   BARTOX  CLAY. 


213 


1766,  an  account  of  the  organic  remains  collected  from  these  Barton  ana 
Hordwell  cliffs,  and  his  excellent  figures  of  the  shells  then  deposited  in 
the  British  Museum  are  justly  admired  by  conchologists  for  their  accuracy. 


SHELLS  OF  THE  BARTON  CLAY,  HANTS. 

Certain  foraminifera  called  Nummulites  begin,  when  we  study  the 
tertiary  formations  in  a  descending  order,  to  make  their  first  appearance 


Fig.  198. 


Fig.  199. 


Fig.  200. 


Fig.  201. 


Mitrascabra,         Valuta  ambigua.        Typhi*  punyens.        Valuta  athteta.    Barton 

and  Bracklesbam. 


Fig.  202. 


Fig.  203. 


Fig.  204. 


Fig.  205. 


TerebeUumfusi-    TerebeUum  con- 
forme.    Barton      volutum.  Lam. 
and  Bracklesham.  Seraphs  convolu- 
tum,  Montf. 


Cardita  globosa. 


Crassatella  sulcata. 


in  these  Barton  beds.  A  small  species  called  Nummulites  variolaria  is 
found  both  on  the  Hampshire  coast  and  in  beds  of  the  same  age  in 
Whitecliff  Bay,  in  the  Isle  of  Wight.  Several  marine  shells,  such  as 
Corbula  pisum,  are  common  to  the  Barton  beds  and  the  Hempstead  or 
Upper  Eocene  series,  and  a  still  greater  number,  as  before  stated,  are 
common  to  the  Headon  series. 

Bagshot  and  Bracklesham  beds,  B.  5. — The  Bagshot  beds,  consisting 
chiefly  of  siliceous  sand,  occupy  extensive  tracts  round  Bagshot,  in  Surrey, 
and  in  the  New  Forest,  Hampshire.  They  may  be  separated  into  three 
divisions,  the  upper  and  lower  consisting  of  light  yellow  sands,  and  the 
central  of  dark  green  sands  and  brown  clays,  the  whole  reposing  on  the 
London  clay  proper.*  The  uppermost  division  is  probably  of  about  the 
same  age  as  the  Barton  series.  Although  the  Bagshot  beds  are  usually 

*  Prest-wich,  Quart.  Geol.  Journ.  vol.  iii.  p.  386. 


214 


EOCENE — BAGSHOT  SANDS. 


[CH.  XVI. 


devoid  of  fossils,  they  contain  marine  shells  in  some  places,  among  which 
Venericardia  planicosta  (see  fig.  206)  is  abundant,  with  Turritella  sul' 
cifera  and  Nummulites  Icevigata.  (See  fig.  210,  p.  215.) 

Fig.  206. 


Venericardia  planicosta^  Lam. 
Cardita  planicosta,  Deshayes. 

At  Bracklesham  Bay,  near  Chichester,  in  Sussex,  the  characteristic 
shells  of  this  member  of  the  Eocene  series  are  best  seen ;  among  others, 
the  huge  Cerithium  giganteum,  so  conspicuous  in  the  calcaire  grossier  of 
Paris,  where  it  is  sometimes  2  feet  in  length.  The  volutes  and  cowries  of 
this  formation,  as  well  as  the  lunulites  and  corals,  seem  to  favor  the  idea 
of  a  warm  climate  having  prevailed,  which  is  borne  out  by  the  discovery 
of  a  serpent,  Palceophis  typhceus  (see  fig.  207),  exceeding,  according  to 

Fig.  207. 


Palceophis  typJimus,  Owen ;  jvn  Eocene  sea-serpent.    Bracklesham. 
|  a,  Z>.  Vertebra,  with  long  neural  spine  preserved.  c.  Two  vertebrae  in  natural  articulation. 

Prof.  Owen,  20  feet  in  length,  and  allied  in  its  osteology  to  the  Boa,  Py 
thon,  Coluber,  and  Hydrus.  The  compressed  form  and  diminutive  size  of 
certain  caudal  vertebrae  indicate  so  much  analogy  with  Hydrus  as  to  in- 
duce the  Hunterian  professor  to  pronounce  this  extinct  ophidian  to  have 
been  marine.*  He  had  previously  combated  with  much  success  the  evi- 
dence advanced  to  prove  the  existence  in  the  Northern  Ocean  of  huge  sea- 
serpents  in  our  own  times,  but  he  now  contends  for  the  former  existence  in 
the  British  Eocene  seas,  of  less  gigantic  serpents,  when  the  climate  was 

*  Palseont.  Soc.  Monograph.  Kept.  pt.  ii.  p.  fil 


CH.  XVI.] 


BRACKLESHAM  BEDS. 


215 


probably  more  genial ;  for  amongst  the  companions  of  the  sea-snake  of 
Bracklesham  was  an  extinct  Gavial  (Gavialis  Dixoni,  Owen),  and  numer- 
ous fish,  such  as  now  frequent  the  seas  of  warm  latitudes,  as  the  sword-fish 
(see  fig.  208),  and  gigantic  rays  of  the  genus  Myliobates  (see  fig.  209). 

Fig.  1208. 


Prolonged  premaxlllary  bone  or  "  sword"  of  a  fossil  sword-fish  (Ccelorhynchui).    Brackl*- 
sham.    Dixon's  Fossils  of  Sussex,  pi.  8. 


Fig.  209. 


Fig.  210. 


Dental  plates  of  Zfyliobatta  Edicardsi. 
Bracklesham  Bay.    Ibid.  pL  8. 


Nummulites  (Num.mula.ria)  Icevigata. 

Bracklesham.    Ibid.  pL  8. 
a.  Section  of  the  nnmnmlite. 
&.  Group,  with  an  individual  showing  the  exterior 


The  teeth  of  sharks  also,  of  the  genera  Carcharodon,  Otodus,  Lamna, 
Galeocerdo,  and  others,  are  abundant.     (See  figs.  211,  212,  213,  214.) 


Fig.  211. 


Fig.  212. 


Fig.2ia 


Fig.  214. 


rcdarod<rr,  \eterodon,  Agass.         Otodut  oMquus,  Agass.     Lamna  elegant,    Galeocerdo  latidens, 

Agaes.  Agass. 

Teeth  of  sharks  from  Bracklesham  Bay. 

The  Nummulites  Icevigata  (see  fig.  210),  so  characteristic  of  the  lower 
beds  of  the  calcaire  Drossier  in  France,  where  it  sometimes  forms  stony 
layers,  as  near  Compiegne,  is  very  common  at  Bracklesham,  together  with 
N.  scabra  and  JV.  variolaria.  Out  of  193  species  of  testacea  procured 
from  the  Bagshot  and  Bracklesham  beds  in  England,  126  occur  in  the 
calcaire  grossier  in  France.  It  was  clearly  therefore  coeval  with  that 
part  of  the  Parisian  series  more  nearly  than  with  any  other. 


216 


LOWER  EOCENE   STRATA  OF  ENGLAND.          [On.  XVI 


MARINE    SHELLS    OF    BRACKLESHAM    BEDS. 
Fig.  216.  Fig.  21T.  FIR.  218. 


Pleurotoma  atten-        Valuta  la-         Turritella,        Lucina  serrata,  Dison.       Oonus  deper* 
uata,  Sow.  trella,  Lam.      multisuleata,  Magnified.  ditus. 

Lam. 

LOWER  EOCENE  FORMATIONS  OF  ENGLAND. 

London  Clay  proper  (C.  1,  Table,  p.  208). — This  formation  underlies 
the  preceding,  and  consists  of  tenacious  brown  and  bluish-gray  clay, 
with  layers  of  concretions  called  septaria,  which  abound  chiefly  in  the 
brown  clay,  and  are  obtained  in  sufficient  numbers  from  sea-cliffs  near 
Harwich,  and  from  shoals  off  the  Essex  coast,  to  be  used  for  making  Ro- 
man cement.  The  principal  localities  of  fossils  in  the  London  clay  are 
Highgate  Hill,  near  London,  the  island  of  Sheppey,  and  Bognor  in  Hamp- 
shire. Out  of  133  fossil  shells,  Mr.  Prestwich  found  only  20  to  be  com- 
mon to  the  calcaire  grossier  (from  which  600  species  have  been  obtained), 
while  33  are  common  to  the  "  Lits  Coquilliers"  (p.  228),  in  which  only 
200  species  are  known  in  France.  We  may  presume,  therefore,  that  the 
Condon  clay  proper  is  older  than  the  calcaire  grossier.  This  may  perhaps 
remove  a  difficulty  which  M.  Adolphe  Brongniart  has  experienced  when 
comparing  the  Eocene  Flora  of  the  neighborhoods  of  London  and  Paris. 
The  fossL  species  of  the  island  of  Sheppey,  he  observes,  indicate  a  much 
more  tropical  climate  than  the  Eocene  Flora  of  France.  Now  the  latter 
has  been  derived  principally  from  the  gypseous  series,  and  resembles  the 
vegetation  of  the  borders  of  the  Mediterranean  Fig.  220. 

rather  than  that  of  an  equatorial  region  ;  whereas 
the  older  flora  of  Sheppey  belongs  to  an  antece- 
dent epoch,  separated  from  the  period  of  the  Paris 
gypsum  by  all  the  calcaire  grossier  and  Bagshot 
series — in  short,  by  the  whole  nummulitic  forma- 
tion properly  so  called. 

Mr.  Bowerbauk,  in  a  valuable  publication  on 
the  fossil  fruits  and  seeds  of  the  island  of  Sheppey, 
near  London,  has  described  no  less  than  thirteen 
fruits  of  palms  of  the  recent  type  Wpa,  now  only 
found  in  the  Molucca  and  Philippine  islands  and  Fossil  palm  of  Sheppey. 
in  Bengal  (see  fig.  220).  In  the  delta  of  the  Ganges,  Dr.  Hooker  ob- 
served the  large  nuts  of  Nipa  fruticans  floating  in  such  numbers  in  the 
various  arms  of  that  great  river,  as  to  obstruct  the  paddle-wheels  of 


CH.  XVL]  FOSSILS  OF  THE   LONDON  CLAY.  217 

steamboats.  These  plants  are  allied  to  the  cocoa-nut  tribe  on  the  one 
side,  and  on  the  other  to  the  Pandanus,  or  screw-pine.  The  fruits  of 
other  palms  besides  those  of  the  cocoa-nut  tribe  are  also  met  with  in  the 
clay  of  Sheppey;  also  three  species  of  Anona,  or  custard-apple;  and 
cucurbitaceous  fruits  (of  the  gourd  and  melon  family)  are  in  considera- 
ble abundance.  Fruits  of  various  species  of  Acacia  are  in  profusion,  and 
these,  although  less  decidedly  tropical,  imply  a  warm  climate. 

The  contiguity  of  land  may  be  inferred  not  only  from  these  vegetable 
productions,  but  also  from  the  teeth  and  bones  of  crocodiles  and  turtles, 
since  these  creatures,  as  Dr.  Conybeare  has  remarked,  must  have  resorted 
to  some  shore  to  lay  their  eggs.  Of  turtles  there  were  numerous  species 
referred  to  extinct  genera.  These  are,  for  the  most  part,  not  equal  in  size 
to  the  largest  living  tropical  turtles.  A  sea-snake,  which  must  have  been 
13  feet  long,  of  the  genus  Palceophis  before  mentioned  (p.  214),  has  also 
been  described  by  Professor  Owen  from  Sheppey,  of  a  different  species 
from  that  of  Bracklesham.  A  true  crocodile,  also,  Crocodilus  toliapicus, 
and  another  saurian  more  nearly  allied  to  the  gavial,  accompany  the 
above  fossils ;  also  the  relics  of  several  birds  and  quadrupeds.  One  of 
these  last  belongs  to  the  new  genus  Hyracotherium  of  Owen,  allied  to  the 
Hyrax,  Hog,  and  Chseropotamus ;  another  is  a  Lophiodon  ;  a  third,  a 
pachyderm  called  Coryphodon  eoccenus  by  Owen,  larger  than  any  existing 
tapir.  All  these  animals  seem  to  have  inhabited  the  banks  of  the  great 
river  which  floated  down  the  Sheppey  fruits.  They  imply  the  existence  of 
a  mammiferous  fauna  antecedent  to  the  period  when  nummulites  flour- 
ished in  Europe  and  Asia,  and  therefore  before  the  Alps,  Pyrenees,  and 
other  mountain-chains  now  forming  the  backbones  of  great  continents, 
were  raised  from  the  deep ;  nay,  even  before  a  part  of  the  constituent 
rocky  masses  now  entering  into  the  central  ridges  of  these  chains  had 
been  deposited  in  the  sea. 

The  marine  shells  of  the  London  clay  confirm  the  inference  derivable 
from  the  plants  and  reptiles  in  favor  of  a  high  temperature.  Thus  many 
species  of  Conus  and  Valuta  occur,  a  large  Cyprcea,  C.  oviformis,  a  very 
large  Rostellaria  (fig.  223),  a  species  of  Canctllaria,  six  species  of  Nau- 
tilus (fig.  225),  besides  other  cephalopoda  of  extinct  genera,  one  of  the 
most  remarkable  of  which  is  the  Belosepia*  (fig.  226).  Among  many 
characteristic  bivalve  shells  are  Leda  amygdaloides  (fig.  227)  and  Axinus 
angulatus  (fig.  228),  and  among  the  Eadiata  a  star-fish  called  Astropec- 
ten  (fig.  229). 

These  fossils  are  accompanied  by  a  sword-fish  (Tetrapterus  priscus, 
Agassiz),  about  8  feet  long,  and  a  saw-fish  (Pristis  bisulcatus,  Ag.),  about 
10  feet  in  length ;  genera  now  foreign  to  the  British  seas.  On  the 
whole,  no  less  than  50  species  of  fish  have  been  described  by  M. 
Agassiz  from  these  beds  in  Sheppey,  and  they  indicate,  in  his  opinion,  a 
warm  climate. 

*  For  description  o^  Eocene  Cephalopoda,  see  Monograph  by  F.  R  Edwards, 
Palaeontograph.  Soc.  1849. 


218 


FOSSIL  SHELLS  OF  THE  LONDON  CLAY.          [Cn.  XVI. 


FOSSIL    SHELLS    OF    THE    LONDON    CLAY. 
Fig-  221.  Fig.  222.  Fig.  228. 


Voluta  nodosa,  Sow.  Phorus  extensus, 

Highgate.  Sow.    Highgate. 

Fig.  224. 


Nautilus  centralis^  Sow.    Highgate. 
Tig.  225. 


Aturia  eicsac,  Brown  and  Edwards. 

Syn.  Nautilus  ziczac,  Sow. 

London  clay.    Sheppey. 


Rostellaria  macroptera,  Sow.  One- 
third  of  nat.  size ;  also  found  in  the 
Barton  clay. 


Fig.  226. 


Belosepia  sepioidea.    Do  Blainv. 
London  clay.    Sheppey. 


Fig.  227.  Fig.  228. 


Leda  amygdaloides, 
Highgate. 


Axinus  angulatus.    London 
clay.    Horusea. 


Fig.  229. 


Astrfipecten  crispatus, 
E.  Forbes.    Sheppey. 


Strata  of  Kyson  in  Suffolk. — At  Kyson,  a  few  miles  east  of  Wood- 
bridge,  a  bed  of  Eocene  clay,  12  feet  thick,  underlies  the  red  crag. 
Beneath  it  is  a  deposit  of  yellow  and  white  sand,  of  considerable  interest, 
in  consequence  of  many  peculiar  fossils  contained  ni  it.  Its  geological 
position  is  probably  the  lowest  part  of  the  London  clay  proper.  In  this 


CH.  XVI]  STRATA  OF  KYSON  IN  SUFFOLK.  219 

sand  has  been  found  the  first  example  of  a  fossil  quadrumanous  animal 
discovered  in  Great  Britain,  namely,  the  teeth  and  rig.  230. 

part  of  a  jaw,  shown  by  Professor  Owen  to  belong 
to  a  monkey  of  the  genus  Macacus  (see  fig.  230). 
The  mammiferous  fossils,  first  met  with  in  the  Molar  of  monkey  (Macacus). 
same  bed,  were  those  of  an  opossum  (Didelphys)  (see  fig.  231),  and  an 
insectivorous  bat  (fig.  232),  together  with  many  teeth  of  fishes  of  the 
shark  family.  Mr.  Colchester  in  1840  obtained  Fi  031 

other  mammalian  relics  from  Kyson,  among 
which  Professor  Owen  has  recognized  several 
teeth  of  the  genus  Hyracotherium,  and  the  ver- 
tebrae of  a  large  serpent,  probably  a  Palceophis. 
As  the  remains  both  of  the  Hyracotherium  and 
Palceophis  were  afterwards  met  with  in  the  Lon-  opossum.  "From  Kyson! 
don  clay,  as  before  remarked,  these  fossils  con- 
firmed the  opinion  previously  entertained,  that 
the  Kyson  sand  belongs  to  the  Eocene  period. 
The  Macacus,  therefore,  constitutes  the  first  exam- 
ple of  any  quadrumanous  animal  occurring  in  strata 

u         J       ••  •  /•       i.  Molars  of  insectivorous  bats, 

so  old  as  the  Eocene,  or  m  a  spot  so  far  from  the  twice  nat.  size, 

equator  as  lat.  52°  K     It  was  not  until  after  the  '  Ky80D' 8u 

year  1836  that  the  existence  of  any  fossil  quadrumana  was  brought  to 
light.  Since  that  period  they  have  been  discovered  in  France,  India,  and 
Brazil. 

Plastic  or  mottled  clays  and  sands  (C.  2,  p.  208). — The  clays  called 
plastic,  which  lie  immediately  below  the  London  clay,  received  their 
name  originally  in  France  from  being  often  used  in  pottery.  Beds  of 
the  same  age  (the  Woolwich  and  Reading  series  of  Prestwich)  are  used 
for  the  like  purposes  in  England.f 

No  formations  can  be  more  dissimilar  on  the  whole  in  mineral  char- 
acter than  the  Eocene  deposits  of  England  and  Paris  ;  those  of  our  own 
island  being  almost  exclusively  of  mechanical  origin, — accumulations  of 
mud,  sand,  and  pebbles ;  while  in  the  neighborhood  of  Paris  we  find  a 
great  succession  of  strata  composed  of  limestones,  some  •  of  them 
siliceous,  and  of  crystalline  gypsum  and  siliceous  sandstone,  and 
sometimes  of  pure  flint  used  for  millstones.  Hence  it  is  by  no 
means  an  easy  task  to  institute  an  exact  comparison  between  the 
various  members  of  the  English  and  French  series,  and  to  settle 
their  respective  ages.  It  is  clear  that,  on  the  sites  both  of  Paris  and 
London,  a  continual  change  was  going  on  in  the  fauna  and  flora  by 
the  coming  in  of  new  species  and  the  dying  out  of  others ;  and 
contemporaneous  changes  of  geographical  conditions  were  also  in 
progress  in  consequence  of  the  rising  and  sinking  of  the  land  and 
bottom  of  the  sea.  A  particular  subdivision,  therefore,  of  time  was 

*  Annals  of  Nat,  Hist  voL  iv.  No.  23,  Nov.  1839. 
f  Prestwich,  Water-bearing  strata  of  London,  1851. 


220 


LOWER  EOCENE  STRATA  OF  ENGLAND.  [On.  XVI 


occasionally  represented  in  one  area  by  land,  in  another  by  an  estuary,  in 
a  third  by  the  sea,  and  even  where  the  conditions  were  in  both  areas  of  a 
marine  character,  there  was  often  shallow  water  in  one,  and  deep  sea  in 
another,  producing  a  want  of  agreement  in  the  state  of  animal  life. 

But  in  regard  to  that  division  of  the  Eocene  series  which  we  have  now 
under  consideration,  we  find  an  exception  to  the  general  rule,  for,  whether 
we  study  it  in  the  basins  of  London,  Hampshire,  or  Paris,  we  recognize 
everywhere  the  same  mineral  character.  This  uniformity  of  aspect  must 
be  seen  in  order  to  be  fully  appreciated,  since  the  beds  consist  simply  ot 
sand,  mottled  clays,  and  well-rolled  flint  pebbles,  derived  from  the  chalk, 
and  varying  in  size  from  that  of  a  pea  to  an  egg.  These  strata  may  be 
seen  in  the  Isle  of  Wight  in  contact  with  the  chalk,  or  in  the  London 
basin,  at  Reading,  Blackheath,  and  Woolwich.  In  some  of  the  lowest  of 
them,  banks  of  oysters  are  observed,  consisting  of  Ostrea  bellovacina,  so 
common  in  France  in  the  same  relative  position,  and  Ostrea  edulina, 
scarcely  distinguishable  from  the  living  eatable  species.  In  the  same 
beds  at  Bromley,  Dr.  Buckland  found  one  large  pebble  to  which  five 
full-grown  oysters  were  affixed,  in  such  a  manner  as  to  show  that  they 
had  commenced  their  first  growth  upon  it,  and  remained  attached  to  it 
through  life. 

In  several  places,  as  at  Woolwich  on  the  Thames,  at  New  Haven  in 
Sussex,  and  elsewhere,  a  mixture  of  marine  and  freshwater  testacea  dis- 
tinguishes this  member  of  the  series.  Among  the  latter,  Milania  inqui- 
nata  (see  fig.  234)  and  Cyrena  cuneiformis  (see  fig.  233)  are  veiy  corn- 


Fig,  233. 


Fig.  234 


Cyrena,  cuneiformis,  Min.  Con. 
Natural  size. 


Melania  inquinata,  Des.    Nat.  size. 
Syn.  Cerithium  melanoides,  Min.  Con. 


mon,  as  in  beds  of  corresponding  age  in  France.  They  clearly  indicate 
points  where  rivers  entered  the  Eocene  sea.  Usually  there  is  a  mixture 
of  brackish,  freshwater,  and  marine  shells,  and  sometimes,  as  at  Woolwich, 


CH.  XVI]  PLASTIC   CLAYS  AND  SANDS.  221 

proofs  of  the  river  and  the  sea  having  successively  prevailed  on  the  same 
spot.  At  New  Charlton,  in  the  suburbs  of  Woolwich,  Mr.  De  la  Conda- 
mine  discovered  in  1849,  and  pointed  out  to  me,  a  layer  of  sand  asso- 
ciated with  well-rounded  flint  pebbles  in  which  numerous  individuals  of 
the  Cyrena  tellinella  were  seen  standing  endwise  with  both  their  valves 
united,  the  posterior  extremity  of  each  shell  being  uppermost,  as  would 
happen  if  the  mollusks  had  died  in  their  natural  position.  I  have  de- 
scribed* a  bank  of  sandy  mud,  in  the  delta  of  the  Alabama  river  at 
Mobile,  on  the  borders  of  the  Gulf  of  Mexico,  where  in  1846  I  dug  out 
at  low  tide  specimens  of  living  species  of  Cyrena  and  of  a  Gnathodon, 
which  were  similarly  placed  with  their  shells  erect,  or  in  a  position 
which  enables  the  animal  to  protrude  its  siphon  upwards,  and  draw 
in  or  reject  water  at  pleasure.  The  water  at  Mobile  is  usually  fresh, 
but  sometimes  brackish.  At  "Woolwich  a  body  of  river  water  must 
have  flowed  permanently  into  the  sea  where  the  Gyrenes  lived,  and 
they  may  have  been  killed  suddenly  by  an  influx  of  pure  salt  water, 
which  invaded  the  spot  when  the  river  was  low,  or  when  a  subsidence 
of  land  took  place.  Traced  in  one  direction,  or  eastward  towards 
Herne  Bay,  the  Woolwich  beds  assume  more  and  more  of  a  marine 
character  ;  while  in  an  opposite,  or  southwestern  direction,  they  become, 
as  near  Chelsea  and  other  places,  more  freshwater,  and  contain  Unio, 
Paludina,  and  layers  of  lignite,  so  that  the  land  drained  by  the  ancient 
river  seems  clearly  to  have  been  to  the  southwest  of  the  present  site  of 
the  metropolis. 

Before  the  minds  of  geologists  had  become  familiar  with  the  theory  of 
the  gradual  sinking  of  land,  and  its  conversion  into  sea  at  different  pe- 
riods, and  the  consequent  change  from  shallow  to  deep  water,  the  fresh- 
water and  littoral  character  of  this  inferior  group  appeared  strange  and 
anomalous.  After  passing  through  hundreds  of  feet  of  London  clay, 
pro  ?ed  by  its  fossils  to  have  been  deposited  in  deep  salt  water,  we  arrive 
at  oeds  of  fluviatile  origin,  and  in  the  same  underlying  formation  masses 
of  shingle,  attaining  at  Blackheath,  near  London,  a  thickness  of  50  feet, 
indicate  the  proximity  of  land,  where  the  flints  of  the  chalk  were  rolled 
into  sand  and  pebbles,  and  spread  continuously  over  wide  spaces.  Such 
shingle  always  appears  at  the  bottom  of  the  series,  whether  in  the  Isle  of 
Wight,  or  in  the  Hampshire  or  London  basins.  It  may  be  asked  why 
they  did  not  constitute  simply  narrow  littoral  zones,  such  as  we  might 
look  for  on  an  ancient  sea-shore.  In  reply,  Mr.  Prestwich  has  suggested 
that  such  zones  of  shingle  may  have  been  slowly  formed  on  a  large  scale 
at  the  period  of  the  Thanet  sands  (C.  3,  p.  208),  and  while  the  land  was 
sinking  the  well-rolled  pebbles  may  have  been  dispersed  simultaneously 
over  considerable  areas,  and  exposed  during  gradual  submergence  to  the 
action  of  the  waves  of  the  sea,  aided  occasionally  by  tidal  currents  and 
river  floods. 

Thanet  sands  (C.  3,  p.  208). — The  mottled  or  plastic  clay  of  the 

*  Second  Visit  to  the  United  States,  yoL  il  p.  101. 


222  EOCENE  STEATA  IN  FKANCE.  [Cn.  XVI. 

Isle  of  Wight  and  Hampshire  is  often  seen  in  actual  contact  with  the 
chalk,  constituting  in  such  places  the  lowest  member  of  the  British  Eo- 
cene series.  But  in  other  points  another  formation  of  marine  origin, 
characterized  by  a  somewhat  different  assemblage  of  organic  remains,  has 
been  shown  by  Mr.  Prestwich  to  intervene  between  the  chalk  and  the 
Woolwich  series.  For  these  beds  he  has  proposed  the  name  of  "  Thanet 
sands,"  because  they  are  well  seen  in  the  Isle  of  Thanet,  in  the  northern 
part  of  Kent,  and  on  the  sea-coast  between  Herne  Bay  and  the  Reculvers, 
where  they  consist  of  sands  with  a  few  concretionary  masses  of  sandstone, 
and  contain  among  other  fossils  Pholadomya  cuneata,  Cyprina  Morrisii, 
Corbula  longirostris,  Scalaria  Bowerbankii,  &c.  The  greatest  thickness 
of  these  beds  is  about  90  feet. 


FRENCH  MIDDLE  EOCENE  FORMATIONS. 
GENERAL  TABLE  OF  FRENCH  EOCENE  STRATA. 

A.    TJPPEK  EOCENE  (Lower  Miocene  of  many  French  authors.) 

English  Equivalents. 

A.  Calcaire  de  la  Beauce,  or  upper  fresh- ) 

water,  see  p.  184,  and  Gres  de  Fon-  >Hempstead  series,  see  p.  192. 
tainebleau,  <fcc.  ) 

B.      MIDDLE  EOCENE. 

B.  2.  Calcaire  siliceux,  (in.  part   eontem-  1 

poraneous    with    the    succeeding  >•  Lower  part  of  the  Bembridge  series. 
group  ?)  ) 

,  3.  Grde  Beaucha^p,  ov  Sables 


i  Lower  Bagshot.  Intermediate  in  age 
between  the  Bracklesham  beds  and 
London  Clay. 

C.      LOWER  EOCENE. 

c.  Argile  plastique  et  lignite. 


The  tertiary  formations  in  the  neighborhood  of  Paris  consist  of  a 
series  of  marine  and  freshwater  strata,  alternating  with  each  other,  and 
filling  up  a  depression  in  the  chalk.  The  area  which  they  occupy  has 
been  called  the  Paris  basin,  and  is  about  180  miles  in  its  greatest 
length,  from  north  to  south,  and  about  90  miles  in  breadth,  from  east 
to  west  (see  Map,  p.  195).  MM.  Cuvier  and  Brongniart  attempted,  in 
1810,  to  distinguish  five  different  groups,  comprising  three  freshwater 


CH.  XVI]        MIDDLE  AND  LOWEK   EOCENE   OF  FRANCE.  223 

and  two  marine,  which  were  supposed  to  imply  that  the  waters  of  the 
ocean,  and  of  rivers  and  lakes,  had  been  by  turns  admitted  into  and 
excluded  from  the  same  area.  Investigations  since  made  in  the  Hamp- 
shire and  London  basins  have  rather  tended  to  confirm  these  views,  at 
least  so  far  as  to  show,  that  since  the  commencement  of  the  Eocene 
period  there  have  been  great  movements  of  the  bed  of  the  sea,  and  of 
the  adjoining  lands,  and  that  the  superposition  of  deep  sea  to  shallow 
water  deposits  (the  London  clay,  for  example,  to  the  Woolwich  beds) 
can  only  be  explained  by  referring  to  such  movements.  Nevertheless,  it 
appears,  from  the  researches  of  M.  Constant  Prevost,  that  some  of  the 
alternations  and  intermixtures  of  freshwater  and  marine  deposits,  in  the 
Paris  basin,  may  be  accounted  for  by  imagining  both  to  have  been  si- 
multaneously in  progress,  in  the  same  bay  of  the  same  sea,  or  a  gulf  into 
which  many  rivers  entered. 

To  enlarge  on  the  numerous  subdivisions  of  the  Parisian  strata,  would 
lead  me  beyond  my  present  limits ;  I  shall  therefore  give  some  examples 
only  of  the  most  important  formations  enumerated  in  the  foregoing 
Table,  p.  222. 

Beneath  the  Upper  Eocene  or  "  Upper  marine  sands,"  A,  already 
spoken  of  (p.  194),  we  find,  in  the  neighborhood  of  Paris,  a  series  of 
white  and  green  marls,  with  subordinate  beds  of  gypsum,  B.  These  are 
most  largely  developed  in  the  central  parts  of  the  Paris  basin,  and, 
among  other  places,  in  the  Hill  of  Montmartre,  where  its  fossils  were  first 
studied  by  M.  Cuvier. 

The  gypsum  quarried  there  for  the  manufacture  of  plaster  of  Paris 
occurs  as  a  granular  crystalline  rock,  and,  together  with  the  associated 
marls,  contains  land  and  fluviatile  shells,  together  with  the  bones  and 
skeletons  of  birds  and  quadrupeds.  Several  land  plants  are  also  met 
with,  among  which  are  fine  specimens  of  the  fan-palm  or  palmetto  tribe 
(Flabellaria).  The  remains  also  of  freshwater  fish,  and  of  crocodiles 
and  other  reptiles,  occur  in  the  gypsum.  The  skeletons  of  mammalia 
are  usually  isolated,  often  entire,  the  most  delicate  extremities  being 
preserved ;  as  if  the  carcasses,  clothed  with  their  flesh  and  skin,  had 
been  floated  down  soon  after  death,  and  while  they  were  still  swoln  by 
the  gases  generated  by  their  first  decomposition.  The  few  accompany- 
ing shells  are  of  those  light  kinds  which  frequently  float  on  the  surface 
of  rivers,  together  with  wood. 

M.  Prevost  has  therefore  suggested  that  a  river  may  have  swept  away 
the  bodies  of  animals,  and  the  plants  which  lived  on  its  borders,  or  in 
the  lakes  which  it  traversed,  and  may  have  carried  them  down  into  the 
centre  of  the  gulf  into  which  flowed  the  waters  impregnated  with  sul- 
phate of  lime.  We  know  that  the  Fiume  Salso  in  Sicily  enters  the  sea 
so  charged  with  various  salts  that  the  thirsty  cattle  refuse  to  drink  of  it. 
A  stream  of  sulphureous  water,  as  white  as  milk,  descends  into  the  sea 
from  the  volcanic  mountain  of  Idienne  on  the  east  of  Java  j  and  a  great 
body  of  hot  water,  charged  with  sulphuric  acid,  rushed  down  from  the 
same  volcano  on  one  occasion,  and  inundated  a  large  tract  of  country. 


224  GYPSEOUS  SERIES.  [Cn.  XVI. 

destroying,  by  its  noxious  properties,  all  the  vegetation.*  In  like  manner 
the  Pusanibio,  or  "  Vinegar  Kiver,"  of  Colombia,  which  rises  at  the  foot 
of  Purace,  an  extinct  volcano,  7,500  feet  above  the  level  of  the  sea,  is 
strongly  impregnated  with  sulphuric  and  hydrochloric  acids  and  with 
oxide  of  iron.  We  may  easily  suppose  the  waters  of  such  streams  to 
have  properties  noxious  to  marine  animals,  and  in  this  manner  the  entire 
absence  of  marine  remains  in  the  ossiferous  gypsum  may  be  explained.f 
There  are  no  pebbles  or  coarse  sand  in  the  gypsum  ;  a  circumstance 
which  agrees  well  with  the  hypothesis  that  these  beds  were  precipitated 
from  water  holding  sulphate  of  lime  in  solution,  and  floating  the  remains 
of  different  animals. 

In  this  formation  the  relics  of  about  fifty  species  of  quadrupeds,  in- 
cluding the  genera  Paleotherium  (see  fig.  191),  Anoplotherium  (see  fig. 
190),  and  others,  have  been  found,  all  extinct,  and  nearly  four-fifths  of 
them  belonging  to  a  division  of  the  order  Pachydermata,  which  is  now 
represented  by  only  four  living  species ;  namely,  three  tapirs  and  the 
daman  of  the  Cape.  With  them  a  few  carnivorous  animals  are  associated, 
among  which  are  the  Jfycenodon  dasyuroides,  and  a  species  of  dog,  Canis 
Parisiensis,  and  a  weasel,  Cynodon  Parisiensis.  Of  the  JKodentia,  are 
found  a  squirrel ;  of  the  Insectivora,  a  bat ;  while  the  Marsupialia  (an 
order  now  confined  to  America,  Australia,  and  some  contiguous  islands) 
are  represented  by  an  opossum. 

Of  birds,  about  ten  species  have  been  ascertained,  the  skeletons  of  some 
of  which  are  entire.  None  of  them  are  referable  to  existing  species.J 
The  same  remark  applies  to  the  fish,  according  to  MM.  Cuvier  and 
Agassiz,  as  also  to  the  reptiles.  Among  the  last  are  crocodiles  and  tor- 
toises of  the  genera  Emis  and  Trionyx. 

The  tribe  of  land  quadrupeds  most  abundant  in  this  formation  is  such 
as  now  inhabits  alluvial  plains  and  marshes,  and  the  banks  of  rivers  and 
lakes,  a  class  most  exposed  to  suffer  by  river  inundations.  Among  these 
were  several  species  of  Paleothere,  a  genus  before  alluded  to  (p.  210). 
These  were  associated  with  the  Anoplotherium,  a  tribe  intermediate  be- 
tween pachyderms  and  ruminants.  One  of  the  three  divisions  of  this 
family  was  called  by  Cuvier  Xiphodon  (see  fig.  235).  Their  forms  were 
slender  and  elegant,  and  one,  named  Xiphodon  gracile  (fig.  235),  was 
about  the  size  of  the  chamois ;  and  Cuvier  inferred  from  the  skeleton  that 
it  was  as  light,  graceful,  and  agile  as  the  gazelle. 

When  the  French  osteologist  declared,  in  the  early  part  of  the  present 
century,  that  all  the  fossil  quadrupeds  of  the  gypsum  of  Paris  were  ex- 
tinct, the  announcement  of  so  startling  a  fact,  on  such  high  authority, 
created  a  powerful  sensation,  and  from  that  time  a  new  impulse  was 
given  throughout  Europe  to  the  progress  of  geological  investigation. 
Eminent  naturalists,  it  is  true,  had  long  before  maintained  that  the  shells 

*  Leyde  Magaz.  voor  Wetensch  Konst  en  Lett,  partie  v.  cahier  i.  p.  71.  Cited 
by  Rozet,  Journ.  de  Geologie,  torn.  i.  p.  43. 

f  M.  C.  Prevost,  Submersions  Iteratives,  <fec.     Note  23. 
j  Cuvier,  Oss.  Fosa.,  torn.  iii.  p.  255. 


CH.  XVI] 


CALCAiRE   SILICEUX. 


and  zoophytes,  met  with  in  many  ancient  European  rocks,  had  ceased  to 
be  inhabitants  of  the  earth,  but  the  majority  even  of  the  educated  classes 

Fig.  235. 


Xiphodon  gracilt,  or  Anoplotherium  gracile,  Curler.    Eestored  outline. 


continued  to  believe  that  the  species  of  animals  and  plants  now  contem- 
porary with  man,  were  the  same  as  those  which  had  been  called  into 
being  when  the  planet  itself  was  created.  It  was  easy  to  throw  discredit 
upon  the  new  doctrine  by  asking  whether  corals,  shells,  and  other  crea- 
tures previously  unknown,  were  not  annually  discovered  ?  and  whether 
living  forms  corresponding  with  the  fossils  might  not  yet  be  dredged  up 
from  seas  hitherto  unexamined  ?  But  from  the  era  of  the  publication  of 
Cuvier's  Ossements  Fossiles,  and  still  more  his  popular  Treatise  called 
"  A  Theory  of  the  Earth,"  sounder  views  began  to  prevail.  It  was  clearly 
demonstrated  that  most  of  the  mammalia  found  in  the  gypsum  of  Mont- 
martre  differed  even  generically  from  any  now  known  to  exist,  and  the 
extreme  improbability  that  any  of  them,  especially  the  larger  ones,  would 
ever  be  found  surviving  in  continents  yet  unexplored,  was  made  manifest. 
Moreover,  the  non-admixture  of  a  single  living  species  in  the  midst  of  so 
rich  a  fossil  fauna  was  a  striking  proof  that  there  had  existed  a  state  of 
the  earth's  surface  zoologically  unconnected  with  the  present  state  of 
things. 

Calcaire  siliceux,  or  Travertin  inferieur,  B.  2. — This  compact  siliceous 
limestone  extends  over  a  wide  area.  It  resembles  a  precipitate  from 
the  waters  of  mineral  springs,  and  is  often  traversed  by  small  empty 
sinuous  cavities.  It  is,  for  the  most  part,  devoid  of  organic  remains, 
but  in  some  places  contains  freshwater  and  land  species,  and  never  any 
marine  fossils.  The  siliceous  limestone  and  the  caleaire  grossier  usually 
occupy  distinct  parts  of  the  Paris  basin,  the  one  attaining  its  fullest  de- 
velopment in  those  places  where  the  other  is  of  slight  thickness.  They 
are  described  by  some  writers  as  alternating  with  each  other  towards 
the  centre  of  the  basin,  as  at  Sergy  and  Osny;  and  M.  Prevost  con- 
cludes, that  while  to  the  north,  where  the  Bay  was  probably  open  to  the 

15 


CALCAIRE  GROSSIER.  [Ca  XVL 

sea,  a  marine  limestone  was  formed,  another  deposit  of  freshwater  origin 
was  introduced  to  the  southward,  or  at  the  head  of  the  bay.  It  is  sup- 
posed that  during  the  Eocene  period,  as  now,  the  ocean  was  to  the  north, 
and  the  continent,  where  the  great  lakes  existed,  to  the  south.  From  that 
southern  region  we  may  suppose  a  body  of  freshwater  to  have  descended, 
charged  with  carbonate  of  lime  and  silica,  the  water  being  perhaps  in 
sufficient  volume  to  freshen  the  upper  end  of  the  bay. 

The  gypsum,  with  its  associated  marl  and  limestone,  is,  as  before  stated, 
in  greatest  force  towards  the  centre  of  the  basin,  where  the  calcaire  gros- 
sier  and  calcaire  siliceux  are  less  fully  developed.  Hence  M.  Prevost 
infers,  that  while  those  two  principal  deposits  were  gradually  in  progress, 
the  one  towards  the  north,  and  the  other  towards  the  'south,  a  river  de- 
scending from  the  east  may  have  brought  down  the  gypseous  and  marly 
sediment. 

Gris  de  Beauchamp  or  Sables  moyens,  B.  3. — In  some  parts  of  the 
Paris  basin,  sands  and  marls,  called  the  Gres  de  Beauchamp,  or  Sables 
moyens,  divide  the  gypseous  beds  from  the  calcaire  grossier  proper.  These 
sands,  in  which  a  small  nummulite  (N.  variolaria)  is  very  abundant,  con- 
tain more  than  300  species  of  marine  shells,  many  of  them  peculiar,  but 
others  common  to  the  next  division. 

Calcaire  grossier,  upper  and  middle,  B.  4. — The  upper  division  of  this 
group  consists  in  great  part  of  beds  of  compact,  fragile  limestone,  with 
some  intercalated  green  marls.  The  shells  in  some  parts  are  a  mixture  of 
Cerithium,  Cyclostoma,  and  Corbula ;  in  others  Limneus,  Cerithium, 
Paludina,  &c.  In  the  latter,  the  bones  of  reptiles  and  mammalia,  Paleo- 
therium  and  Lophiodon,  have  been  found.  The  middle  division,  or  cal- 
caire grossier  proper,  consists  of  a  coarse  limestone,  often  passing  into 
sand.  It  contains  the  greater  number  of  the  fossil  shells  which  character- 
ize the  Paris  basin.  No  less  than  400  distinct  species  have  been  pro- 
cured from  a  single  spot  near  Grignon,  where  they  are  imbedded  in  a 
calcareous  sand,  chiefly  formed  of  comminuted  shells,  in  which,  never- 
theless, individuals  in  a  perfect  state  of  preservation,  both  of  marine, 
terrestrial,  and  freshwater  species,  are  mingled  together.  Some  of 
the  marine  shells  may  have  lived  on  the  spot ;  but  the  Cyclostoma 
and  Limneus  must  have  been  brought  thither  by  rivers  and  currents, 
and  the  quantity  of  triturated  shells  implies  considerable  movement  in 
the  waters. 

Nothing  is  more  striking  in  this  assemblage  of  fossil  testacea  than  the 
great  proportion  of  species  referable  to  the  genus  Cerithium  (see  p.  30, 
fig.  44).  There  occur  no  less  than  137  species  of  this  genus  in  the  Paris 
basin,  and  almost  all  of  them  in  the  calcaire  grossier.  Most  of  the  living 
Cerithia  inhabit  the  sea  near  the  mouths  of  rivers,  where  the  waters 
are  brackish ;  so  that  their  abundance  in  the  marine  strata  now  under 
consideration  is  in  harmony  with  the  hypothesis,  that  the  Paris  basin 
formed  a  gulf  into  which  several  rivers  flowed,  the  sediment  of  some 
of  which  gave  rise  to  the  beds  of  clay  and  lignite  before  mentioned ; 
while  a  distinct  freshwater  limestone,  called  calcaire  siliceux,  already 


CH    XVL] 


EOCENE   FORAMINIFERA. 


227 


described,  was  precipitated  from  the  waters  of  others  situated  farther  to 
the  south. 

In  some  parts  of  the  calcaire  grossier  round  Paris,  certain  beds  occur 
of  a  stone  used  in  building,  and  called  by  the  French  geologists  "  Miliolite 
limestone."  It  is  almost  entirely  made  up  of  millions  of  microscopic 
shells,  of  the  size  of  minute  grains  of  sand,  which  all  belong  to  the  class 
Foraminifera.  Figures  of  some  of  these  are  given  in  the  annexed  wood- 
cut. As  this  miliolitic  stone  never  occurs  in  the  Faluns,  or  Miocene  strata 


EOCENE    FORAMINIFERA. 


Fig.  236. 


Fig.  237. 


Calcarina  rarispina,  Desh. 
b.  Natural  size.        a.  e.  Same  magnified. 


SjArolina  etenostoma,  Desh. 
B.  Natural  size.     A,  C.  D.  Same  magnified. 


Fig.  238. 


TrilocvUna  injtata,  Desh. 
&.  Natural  size.       a,  e,  d.  Same  magnified. 

Fig.  239. 


ClavuHna  comtgata,  Desh. 
Natural  size.        5,  e.  Same  magnified. 


of  Brittany  and  Tourame,  it  often  furnishes  the  geologist  with  a  useful 
criterion  for  distinguishing  the  detached  Eocene  and  Miocene  forma- 
tions, scattered  over  those  and  other  adjoining  provinces.  The  dis- 
covery of  the  remains  of  Paleotherium  and  other  mammalia  in  some 
of  the  upper  beds  of  the  calcaire  grossier  shows  that  these  land  animals 
began  to  exist  before  the  deposition  of  the  overlying  gypseous  series 
had  commenced. 


228 


LITS   COQUILLIEES. 


[Cn.  XVI 


Lower  Calcaire  grassier,  or  Glauconie  grossier  e,  B.  5. — The  lower  part 
of  the  calcaire  grossier,  which  often  contains  much  green  earth,  is  char- 
acterized at  Auvers,  near  Pontoise,  to  the  north  of  Paris,  and  still  more 
in  the  environs  of  Compiegne,  by  the  abundance  of  nummulites,  con- 
sisting chiefly  of  N.  Icevigata,  N.  scabra,  and  N.  Lamarcki,  which  con- 
stitute a  large  proportion  of  some  of  the  stony  strata,  though  these  same 
foraminifera  are  wanting  in  beds  of  similar  age  in  the  immediate  environs 
of  Paris. 

Soissonnais  Sands  or  Lits  coquilliers,  B.  6. — Below  the  preceding 
formation,  shelly  sands  are  seen,  of  considerable  thickness,  especially  at 
Cuisse-Lamotte,  near  Compiegne,  and  other  localities  in  the  Soissonnais, 
about  fifty  miles  N.  E.  of  Paris,  from  which  about  300  species  of  shells 
have  been  obtained,  many  of  them  common  to  the  Calcaire  grossier  and 
the  Bracklesham  beds  of  England,  and  many  peculiar.  The  Nummulites 
planulata  is  very  abundant,  and  the  most  characteristic  shell  is  the 
Nerita  conoidea,  Lam.,  a  fossil  which  has  a  very  wide  geographical 

Fig.  240. 


Iferita  conoidea,  Lam. 
Byn.  2f.   Schmidelliana,  Chemnitz. 

range  ;  for,  as  M.  D'Archiac  remarks,  it  accompanies  the  nummulitic  for- 
mation from  Europe  to  India,  having  been  found  in  Cutch,  near  the 
mouths  of  the  Indus,  associated  with  Nummulites  scabra.  No  less  than 
thirty-three  shells  of  this  group  are  said  to  be  identical  with  shells  of  the 
London  clay  proper,  yet,  after  visiting  Cuisse-Lamotte  and  other  localities 
of  the  "  Sables  inferieures"  of  Archiac,  I  agree  with  Mr.  Prestwich,  that 
the  latter  are  probably  newer  than  the  London  clay,  and  perhaps  older 
than  the  Bracklesham  beds  of  England.  The  London  clay  seems  to  be 
unrepresented  in  France,  unless  partially  so,  by  these  sands.*  One  of  the 
shells  of  the  sandy  beds  of  the  Soissonnais  is  adduced  by  M.  Deshayes  as 

Fig.  241. 


Cardium  porulosum.    Paris  and  London  basins, 
*  D'Archiac,  Bulletin,  torn.  x. ;  and  Prestwich,  Geol.  Quart.  Journ.  1847,  p.  371 


CH.  XVI.]  NUMMULITIC  FORMATIONS.  229 

an  example  of  the  changes  which  certain  species  underwent  in  the  succes- 
sive staares  of  their  existence.  It  seems  that  different  varieties  of  the 

O 

Cardium  porulosum  are  characteristic  of  different  formations.  In  the 
Soissonnais  this  shell  acquires  but  a  small  volume,  and  has  many  pecu- 
liarities, which  disappear  in  the  lowest  beds  of  the  calcaire  grossier.  In 
these  the  shell  attains  its  full  size,  with  many  distinctive  characters,  which 
are  again  modified  in  the  uppermost  beds  of  the  calcaire  grossier ;  and 
these  last  modifications  of  form  are  preserved  throughout  the  "  upper 
marine"  (or  Upper  Eocene)  series.* 

Argile  plastique  (C,  Table,  p.  222). — At  the  base  of  the  tertiary  system 
in  France  are  extensive  deposits  of  sands,  with  occasional  beds  of  clay 
used  for  pottery,  and  called  "  argile  plastique."  Fossil  oysters  ( Ostrea 
bellovacina)  abound  in  some  places,  and  in  others  there  is  a  mixture  of 
fluviatile  shells,  such  as  Cyrena  cuneiformis  (fig.  233,  p.  220),  Melanin 
inquinata  (fig.  234),  and  others,  frequently  met  with  in  beds  occupying 
the  same  position  in  the  valley  of  the  Thames.  Layers  of  lignite  also 
accompany  the  inferior  clays  and  sands. 

Immediately  upon  the  chalk  at  the  bottom  of  all  the  tertiary  straw  in 
France  there  generally  is  a  conglomerate  or  breccia  of  rolled  and  angular 
chalk-flints,  cemented  by  siliceous  sand.  These  beds  appear  to  be  of  lit- 
toral origin,  and  imply  the  previous  emergence  of  the  chalk,  and  its  waste 
by  denudation. 

Whether  the  Thanet  sands  before  mentioned  (p.  221)  are  exactly  rep- 
resented in  the  Paris  basin,  is  still  a  matter  of  discussion. 

Wide  extent  of  the  nummulitic  formation  in  Europe,  Asia,  <&c. — When 
I  visited  Belgium  and  French  Flanders  in  1851,  with  a  view  of  com- 
paring the  tertiary  strata  of  those  countries  with  the  English  series,  I 
found  that  all  the  beds  between  the  Upper  Eocene  or  Limburg  formations, 
and  the  Lower  Eocene  or  London  clay  proper,  might  be  conveniently 
divided  into  three  sections,  distinguished,  among  other  paleontological 
characters,  by  three  different  species  of  nummulites,  JV.  variolaria  in  the 
upper  beds,  N.  loevigata  in  the  middle,  and  N.  planulata  in  the  lower. 
After  I  had  adopted  this  classification,  I  found,  what  I  had  overlooked  or 
forgotten,  that  the  superposition  of  these  three  species  in  the  order  here 
assigned  to  them,  had  been  previously  recognized  in  the  North  of  France, 
in  1842,  by  Viscount  D'Archiac.  The  same  author,  in  the  valuable 
monograph  recently  published  by  him,f  has  observed,  that  a  somewhat 
similar  distribution  of  these  and  other  species  in  time,  prevails  very 
widely  in  the  South  of  France  and  the  Pyrenees,  as  well  as  in  the  Alps 
and  Apennines,  and  in  Istrea, — the  lowest  nummulitic  beds  being  charac- 
terized by  fewer  and  smaller  species,  the  middle  by  a  greater  number  and 
by  those  which  individually  attain  the  largest  dimensions,  and  the  upper- 
most beds  again  by  small  species. 

In  the  treatise  alluded  to,  M.  D'Archiac  describes  no  less  than  fifty  - 
two  species  of  this  genus,  and  considers  that  they  are  all  of  them  char- 

*  Coquilles  caract&ristiques  des  terrains,  1831. 

f  Animaux  foss.  du  groupe  nummul.  de  1'Inde  :  Paris,  1853. 


230  NUMMULITIC  FORMATIONS  IN  EUROPE,  ETC,    [On.  XVI. 

acteristic  of  those  tertiary  strata  which  I  have  called  Middle  Eocene.  In 
very  few  instances  at  least  do  certain  species  diverge  from  this  narrow 
limit,  whether  into  incumbent  or  subjacent  tertiary  formations,  it  being 
rather  doubtful  whether  more  than  one  of  them,  Nummulites  intermedia, 
also  a  Middle  Eocene  fossil,  ascends  so  high  as  the  Miocene  formation,  or 
whether  any  of  them  descend  to  the  level  of  the  London  clay.  Certainly 
they  have  never  been  traced  so  low  down  as  the  marine  beds,  coeval 
with  the  Plastic  clay  or  Lignite,  in  any  country  of  which  the  geology  has 
been  well  worked  out.  This  conclusion  is  a  very  unexpected  result  of 
recent  inquiry,  since  for  many  years  it  was  a  matter  of  controversy 
whether  the  nummulitic  rocks  of  the  Alps  and  Pyrenees  ought  not  to  be 
regarded  as  cretaceous  rather  than  Eocene.  The  late  M.  Alex.  Brongniart 
first  declared  the  specific  identity  of  many  shells  of  the  marine  strata  near 
Paris,  and  those  of  the  nummulitic  formation  of  Switzerland,  although  he 
obtained  these  last  from  the  summit  of  the  Diablerets,  one  of  the  loftiest 
of  the  Swiss  Alps,  which  rises  more  than  10,000  feet  above  the  level  of 
the  sea. 

The  nummulitic  limestone  of  the  Alps  is  often  of  great  thickness,  and 
is  immediately  covered  by  another  series  of  strata  of  dark-colored  slates, 
marls,  and  fucoidal  sandstones,  to  the  whole  of  which  the  provincial  name 
of  "  flysch"  has  been  given  in  parts  of  Switzerland.  The  researches  of 
Sir  Roderick  Murchison  in  the  Alps  in  1847  have  shown  that  all  these 
tertiary  strata  enter  into  the  disturbed  and  loftiest  portions  of  the  Alpine 
chain,  to  the  upheaval  of  which  they  enable  us  therefore  to  assign  a  com- 
paratively modern  date. 

The  nummulitic  formation,  with  its  characteristic  fossils,  plays  a  far  more 
conspicuous  part  than  any  other  tertiary  group  in  the  solid  framework  of 
the  earth's  crust,  whether  in  Europe,  Asia,  or  Africa.  It  often  attains  a 
thickness  of  many  thousand  feet,  and  extends  from  the  Alps  to  the  Car- 
pathians, and  is  in  full  force  in  the  north  of  Africa,  as,  for  example,  in 
Algeria  and  Morocco.  It  has  also  been  traced  from  Egypt,  where  it  was 
largely  quarried  of  old  for  the  building  of  the  Pyramids,  into  Asia  Minor, 
and  across  Persia  by  Bagdad  to  the  mouths  of  the  Indus.  It  occurs  not  only 
in  Cutch,  but  in  the  mountain  ranges  which  separate  Scinde  from  Persia,  and 
which  form  the  passes  leading  to  Caboul ;  and  it  has  been  followed  still  far- 
ther eastward  into  India,  as  far  as  eastern  Bengal  and  the  frontiers  of  China. 

Fig.  242. 


Nummulites  Puschi,  D'Archlac.    Peyrehoradc,  Pyrenees. 

a.  External  surface  of  one  of  the  nummulites,  of  which  longitudinal  sections  are  seen  in  the 

limestone. 
T>.  Transverse  section  of  same. 


CH.  XVL]  EOCENE  STRATA. 

Dr.  T.  Thomson  found  nummulites  at  an  elevation  of  no  less  than 
1 6,500  feet  above  the  level  of  the  sea,  in  Western  Thibet. 

One  of  the  species,  which  I  myself  found  very  abundant  on  the  flanks 
of  the  Pyrenees,  in  a  compact  crystalline  marble  Fig.  248. 

(fig.  242)  is  called  by  M.  D'Archiac  Nummulites 
Puschi.  The  same  is  also  very  common  in  rocks  of 
the  same  age  in  the  Carpathians. 

Another  large  species  (see  fig.  243),  Nummulites 
exponens,  J.  Sow.,  occurs  not  only  in  the  South  of 
France,  near  Dax,  but  in  Germany,  Italy,  Asia  Minor, 
and  in  Cutch ;  also  in  the  mountains  of  Sylhet,  on  the 
frontiers  of  China.  *"*'  Europe  "* Indta- 

In  many  of  the  distant  countries  above  alluded  to,  in  Cutch,  for  exam- 
ple, some  of  the  same  shells,  such  as  Nerita  conoidea  (Hg.  240),  accom- 
pany the  Nummulites  as  in  France. 

The  opinion  of  many  observers,  that  the  nummulitic  formation  belongs 
partly  to  the  cretaceous  era,  seems  chiefly  to  have  arisen  from  confound- 
ing an  allied  genus,  Orbitoides,  with  the  true  Nummulite. 

When  we  have  once  anived  at  the  conviction  that  the  nummulitic  for- 
mation occupies  a  middle  place  in  the  Eocene  series,  we  are  struck  with 
the  comparatively  modern  date  to  which  some  of  the  greatest  revolutions 
in  the  physical  geography  of  Europe,  Asia,  and  Northern  Africa  must  be 
referred.  All  the  mountain  chains,  such  as  the  Alps,  Pyrenees,  Carpa- 
thians, and  Himalayas,  into  the  composition  of  whose  central  and  loftiest 
parts  the  nummulitic  strata  enter  bodily,  could  have  had  no  existence  till 
after  the  Middle  Eocene  period.  During  that  period  the  sea  prevailed 
where  these  chains  now  rise,  for  nummulites  and  their  accompanying  tes- 
tacea  were  unquestionably  inhabitants  of  salt  water.  Before  these  events, 
comprising  the  conversion  of  a  wide  area  from  a  sea  to  a  continent,  Eng- 
land had  been  peopled,  as  I  before  pointed  out  (p.  219),  by  various 
quadrupeds,  by  herbivorous  pachyderms,  by  insectivorous  bats,  by  opos- 
sums and  monkeys. 

Almost  all  the  extinct  volcanoes  which  preserve  any  remains  of  their 
oriafinal  form,  or  from  the  craters  of  which  lava  streams  can  be  traced, 

O 

are  more  modern  than  the  Eocene  fauna  now  under  consideration  ;  and 
besides  these  superficial  monuments  of  the  action  of  heat,  Plutonic  influ- 
ences have  worked  vast  changes  in  the  texture  of  rocks  within  the  same 
period.  Some  members  of  the  nummulitic  and  overlying  tertiary  strata 
called  flysch  have  actually  been  converted  in  the  Central  Alps  into  crys- 
talline rocks,  and  transformed  into  marble,  quartz-rock,  mica-schist, -and 
gneiss.* 

EOCENE    STRATA    IN    THE    UNITED    STATES. 

In  North  America  the  Eocene  formations  occupy  a  large  area 
bordering  the  Atlantic,  which  increases  in  breadth  and  importance  as 
it  is  iraced  southwards  from  Delaware  and  Maryland  to  Georgia  and 

*  Mnrchison,  Quart.  Journ.  of  Geol.  Soc.  vol.  v.,  and  Lyell,  vol.  vl  1850,  Anni- 
versary  Address. 


232  EOCENE  STKATA  IN  UNITED  STATES.  [Cfl.  XVI 

Alabama.  The}7  also  occur  in  Louisiana  and  other  states  both  east  and 
west  of  the  valley  of  the  Mississippi.  At  Claiborne  in  Alabama  no  less 
than  400  species  of  marine  shells,  with  many  echinoderms  and  teeth  of 
fish,  characterize  one  member  of  this  system.  Among  the  shells,  the 
Cardita  planicosta,  before  mentioned  (fig.  216,  p.  214),  is  in  abundance; 
and  this  fossil,  and  some  others  identical  with  European  species,  or  very 
nearly  allied  to  them,  make  it  highly  probable  that  the  Claiborne  beds 
agree  in  age  with  the  central  or  Bracklesham  group  of  England,  and  with 
the  calcaire  grossier  of  Paris.* 

Higher  in  the  series  is  a  remarkable  calcareous  rock,  formerly  called 
"  the  nummulite  limestone,"  from  the  great  number  of  discoid  bodies 
resembling  nummulites  which  it  contains,  fossils  now  referred  by  A. 
d'Orbigny  to  the  genus  Orbitoides,  which  has  been  demonstrated  by  Dr. 
Carpenter  to  belong  to  the  foraminifera.j  That  naturalist  moreover  is 
of  opinion  that  the  Orbitoides  alluded  to  (0.  Mantelli)  is  of  the  same 
species  as  one  found  in  Cutch  in  the  Middle  Eocene  or  nummulitic  forma- 
tion of  India.  The  following  section  will  enable  the  reader  to  understand 
the  position  of  three  subdivisions  of  the  Eocene  series,  Nos.  1,  2,  and  3, 
the  relations  of  which  I  ascertained  in  Clarke  County,  between  the  rivers 
Alabama  and  Tombeckbee. 


1.  Sand,  marl,  &c.,  -with  numerous  fossils.  ) 

2.  White  or  rotten  limestone,  with  Zeuglodon.       V  Eocene. 

3.  Orbitoidsl,  or  so  called  nummulitic,  limestone.    ) 

4.  Overlying  formation  of  sand  and  clay  without  fossils.    Age  unknown. 

The  lowest  set  of  strata,  No.  1,  having  a  thickness  of  more  than  100 
feet,  comprise  marly  beds,  in  which  the  Ostrea  sellceformis  occurs,  a  shell 
ranging  from  Alabama  to  Virginia,  and  being  a  representative  form  of 
the  Ostrea  flabellula  of  the  Eocene  group  of  Europe.  In  other  beds  of 
No.  1,  two  European  shells,  Cardita  planicosta,  before  mentioned,  and 
Solarium  canaliculatum,  are  found,  with  a  great  many  other  species  pe- 
culiar to  America.  Numerous  corals,  also,  and  the  remains  of  placoid 
fish  and  of  rays,  occur,  and  the  "  swords,"  as  they  are  called,  of  sword 
fishes,  all  bearing  a  great  generic  likeness  to  those  of  the  Eocene  strata  of 
England  and  France. 

No.  2  (fig.  244)  is  a  white  limestone,  sometimes  soft  and  argillaceous, 

*  See  paper  by  the  author,  Quart.  Journ.  Geol.  Soc.  vol.  iv.  p.  12;  and  Second 
Visit  to  the  U.  S.  vol.  ii.  p.  59. 
f  Quart.  Journ.  Geol.  Soc.  vol.  vi.  p.  32. 


CH.  X.VI.J  EOCENE   STKATA   IN   UNITED   STATES.  233 

but  in  parts  very  compact  and  calcareous.  It  contains  several  peculiar 
corals,  and  a  large  Nautilus  allied  to  ^V.  ziczac  ;  also  in  its  upper  bed  a 
gigantic  cetacean,  called  Zeuglodon  by  Owen.* 

Fig.  245.  Fig.  246. 


Zeuglodon  cetoides,  Owen. 
Sasilosaurus,  Harlan. 
Fig.  245.  Molar  tooth,  natural  size.  Fig.  246.  Vertebra,  reduced. 

The  colossal  bones  of  this  cetacean  are  so  plentiful  in  the  interior  of 
Clarke  County  as  to  be  characteristic  of  the  formation.  The  vertebral 
column  of  one  skeleton  found  by  Dr.  Buckley  at  a  spot  visited  by  me, 
extended  to  the  length  of  nearly  70  feet,  and  not  far  off  part  of  another 
backbone  nearly  50  feet  long  was  dug  up.  I  obtained  evidence,  during 
a  short  excursion,  of  so  many  localities  of  this  fossil  animal  within  a  dis- 
tance of  10  miles,  as  to  lead  me  to  conclude  that  they  must  have  belonged 
to  at  least  forty  distinct  individuals. 

Prof.  Owen  first  pointed  out  that  this  huge  animal  was  not  reptilian, 
since  each  tooth  was  furnished  with  double  roots  (see  fig.  245),  implanted 
in  corresponding  double  sockets ;  and  his  opinion  of  the  cetacean  nature 
of  the  fossil  was  afterwards  confirmed  by  Dr.  Wyrnan  and  Dr.  R.  "W. 
Gibbes.  That  it  was  an  extinct  mammal  of  the  whale  tribe  has  since 
been  placed  beyond  all  doubt  by  the  discovery  of  the  entire  skull  of  an- 
other fossil  species  of  the  same  family,  having  the  double  occipital  con- 
dyles  only  met  with  in  mammals,  and  the  convoluted  tympanic  bones 
which  are  characteristic  of  cetaceans. 

Near  the  junction  of  No.  2  and  the  incumbent  limestone,  No.  3,  next 
to  be  mentioned,  are  strata  characterized  by  the  following  shells :  Spon- 
dylus  dumosus  (Plagiostoma  dumosum,  Morton,)  Pecten  Poulsoni,  Pecten 
perplanus,  and  Ostrea  cretacea. 

.  No.  3  (fig.  244)  is  a  white  limestone,  for  the  most  part  made  up  of  the 
Orbitoides  of  D'Orbigny  before  mentioned  (p.  232),  formerly  supposed 
to  be  a  nummulite,  and  called  W.  Mantelli,  mixed  -with  a  few  lunulites, 
some  small  corals,  and  shells.f  The  origin,  therefore,  of  this  cream- 
colored  soft  stone,  like  that  of  our  white  chalk,  which  it  much  resembles, 
is,  I  believe,  due  to  the  decomposition  of  these  foraminifera.  The  surface  of 
the  country  where  it  prevails  is  sometimes  marked  by  the  absence  of  wood, 

*  See  Memoir  by  R.  W.  Gibbes,  Journ.  of  Acad.  Nat.  Sci.  Philad.  voL  i.  1847. 
f  Lyell,  Quart.  Journ.  GeoL  Soc.  1847,  voL  iv.  p.  15. 


234:  CKETACEOUS  GROUPS.  [On.  XV  Q 

like  our  chalk  downs,  or  is  covered  exclusively  by  the  Juniperus  Virgini- 
ana,  as  certain  chalk  districts  in  England  by  the  yew-tree  and  juniper. 

Some  of  the  shells  of  this  limestone  are  common  to  the  Claiborne  beds, 
but  many  of  them  are  peculiar. 

It  will  be  seen  in  the  section  (fig.  244,  p.  232)  that  the  strata  of  Nos. 
1,  2,  3  are,  for  the  most  part,  overlaid  by  a  dense  formation  of  sand  or  clay 
without  fossils.  In  some  points  of  the  bluff  or  cliff  of  the  Alabama  river, 
at  Claiborne,  the  beds  Nos.  1,  2  are  exposed  nearly  from  top  to  bottom, 
whereas  at  other  points  the  newer  formation,  No.  4,  occupies  the  face  of 
nearly  the  whole  cliff.  The  age  of  this  overlying  mass  has  not  yet  been 
determined,  as  it  has  hitherto  proved  destitute  of  organic  remains. 

The  burr-stone  strata  of  the  Southern  States  contain  so  many  fossils 
agreeing  with  those  of  Claiborne,  that  it  doubtless  belongs  to  the  same  part 
of  the  Eocene  group,  though  I  was  not  fortunate  enough  to  see  the  rela- 
tions of  the  two  deposits  in  a  continuous  section.  Mr.  Tuomey  considers 
it  as  the  lower  portion  of  the  series.  It  may,  perhaps,  be  a  form  of  the 
Claiborne  beds  in  places  where  lime  was  wanting,  and  where  silex,  derived 
from  the  decomposition  of  felspar,  predominated.  It  consists  chiefly  of 
slaty  clays,  quartzose  sands,  and  loam,  of  a  brick-red  color,  with  layers  of 
chert  or  burr-stone,  used  in  some  places  for  mill-stones. 


CHAPTER  XVII. 

CRETACEOUS  GROUP. 

Lapse  of  time  between  the  Cretaceous  and  Eocene  periods — "Whether  certain 
formations  in  Belgium  and  France  are  of  intermediate  age — Pisolitic  limestone 
— Divisions  of  the  Cretaceous  series  in  Northwestern  Europe — Maestricht  beds 
— Chalk  of  Faxoe — "White  chalk — Its  geographical  extent  and  origin — Formed 
in  an  open  and  deep  sea — How  far  derived  from  shells  and  corals — Single 
pebbles  in  chalk — Chalk  flints — Potstones  of  Horstead — Fossils  of  the  Upper 
Cretaceous  rocks — Echinoderms,  Mollusca,  Bryozoa,  Sponges — Upper  Green- 
sand  and  Gault — Chalk  of  South  of  Europe — Hippurite  limestone — Cretaceous 
rocks  of  the  United  States. 

HAVING  treated  in  the  preceding  chapters  of  the  tertiary  strata,  we  have 
next  to  speak  of  the  uppermost  of  the  secondary  groups,  commonly  called 
the  chalk,  or  the  cretaceous  strata,  from  creta,  the  Latin  name  for  that 
remarkable  white  earthy  limestone,  which  constitutes  an  upper  member  of 
the  group  in  these  parts  of  Europe,  where  it  was  first  studied.  The  marked 
discordance  in  the  fossils  of  the  tertiary,  as  compared  with  the  cretaceous 
formations,  has  long  induced  many  geologists  to  suspect  that  an  indefinite 
series  of  ages  elapsed  between  the  respective  periods  of  their  origin. 
Measured,  indeed,  by  such  a  standard,  that  is  to  say,  by  the  amount  of 
change  in  the  Fauna  and  Flora  of  the  earth  effected  in  the  interval,  the 
time  between  the  cretaceous  and  Eocene  may  have  been  as  great  as  that 


CH.  XVIL]  PISOLITIC  LIMESTONE  OF  FRANCE.  235 

between  the  Eocene  and  recent  periods,  to  the  history  of  which  the  last 
seven  chapters  have  been  devoted.  Several  fragmentary  deposits  have 
been  met  with  here  and  there,  in  the  course  of  the  last  half  century,  of  an 
age  intermediate  between  the  white  chalk  and  the  plastic  clays  and  sands, 
of  the  Paris  and  London  districts,  monuments  which  have  the  same  kind 
of  interest  to  a  geologist,  which  certain  mediaeval  records  excite  when  we 
study  the  history  of  nations.  For  both  of  them  throw  light  on  ages  of 
darkness,  preceded  and  followed  by  others  of  which  the  annals  are  com- 
paratively well  known  to  us.  But  these  newly  discovered  records  do  not 
fill  up  the  wide  gap,  some  of  them  being  closely  allied  to  the  Eocene,  and 
others  to  the  cretaceous  type,  while  none  appear  as  yet  to  possess  so  dis- 
tinct and  characteristic  a  fauna,  as  may  entitle  them  to  hold  an  indepen- 
dent place  in  the  great  chronological  series. 

Among  the  formations  alluded  to,  the  Thanet  Sands  of  Prestwich  have 
been  sufficiently  described  in  the  last  chapter,  and  classed  as  Lower  Eo- 
cene. To  the  same  tertiary  series  belong  the  Belgian  formations,  called 
by  Professor  Dumont,  Landenian  and  Heersian,  although  these  are  prob- 
ably of  higher  antiquity  than  the  Thanet  Sands.  On  the  other  hand,  the 
Maestricht  and  Faxoe  limestones  are  very  closely  connected  with  the 
chalk,  to  which  also  the  Pisolitic  limestone  of  France  has  been  recently 
referred  by  high  authorities. 

The  Lower  Landenian  beds  of  Belgium  consist  of  marls  and  sands,  often 
containing  much  green  earth,  called  glauconite.  They  may  be  seen  at 
Tournay,  and  at  Angres,  near  Mons,  and  at  Orp-le-Grand,  Lincent,  and 
Landen  in  the  ancient  provin'ce  of  Hesbaye,  in  Belgium,  where  they 
supply  a  durable  building-stone,  yet  one  so  light  as  to  be  easily  trans- 
ported. Some  few  shells  of  the  genus  Pholodamya,  Scalaria,  and  others, 
agree  specifically  with  fossils  of  the  Thanet  Sands ;  but  most  of  them, 
such  as  Astarte  incequilatera,  Nyst,  are  peculiar.  In  the  building-stone 
of  Orp-le-Grand,  I  found  a  Cardiaster,  a  genus  which,  according  to 
Professor  E.  Forbes,  was  previously  unknown  in  rocks  newer  than  the 
cretaceous. 

Still  older  than  the  Lower  Landenian  is  the  marl,  or  calcareous  glau- 
conite of  the  village  of  Heers,  near  Waremme,  in  Belgium ;  also  seen  at 
Marlinne  in  the  same  district,  where  I  have  examined  it.  It  has  been 
sometimes  classed  with  the  cretaceous  series,  although  as  yet  it  has 
yielded  no  forms  of  a  decidedly  cretaceous  aspect,  such  as  Ammonite, 
Baculite,  Belemnite,  Hippurite,  &c.  The  species  of  shells  are  for  the 
most  part  new ;  but  it  contains,  according  to  M.  Hebert,  Pholodamya 
cuneata,  an  Eocene  fossil,  and  he  assigns  it  with  confidence  to  the  tertiary 


Pisolitic  limestone  of  France. — Geologists  have  been  still  more  at 
variance  respecting  the  chronological  relations  of  this  rock,  which  is 
met  with  in  the  neighborhood  of  Paris,  and  at  places  north,  south, 
east,  and  west  of  that  metropolis,  as  between  Vertus  and  Laversines, 
Meudon  and  Montereau.  It  is  usually  in  the  form  of  a  coarse  yellow- 
ish or  whitish  limestone,  and  the  total  thickness  of  the  series  of  beds, 


236  CLASSIFICATION  OF  CEETACEOUS  ROCKS.       [On.  XVIL 

already  known  is  about  100  feet.  Its  geographical  range,  according  tc 
M.  Hebert,  is  not  less  than  45  leagues  from  east  to  west,  and  35  from 
north  to  south.  Within  these  limits  it  occurs  in  small  patches  only,  rest- 
ing unconformably  on  the  white  chalk.  It  was  originally  regarded  as 
cretaceous  by  M.  E.  de  Beaumont,  on  the  ground  of  its  having  undergone, 
like  the  white  chalk,  extensive  denudation  previous  to  the  Eocene  period ; 
but  many  able  paleontologists,  and  among  others  MM.  C.  D'Orbigny, 
Deshayes,  and  D'Arcniac,  disputed  this  conclusion,  and,  after  enumerating 
54  species  of  fossils,  declared  that  their  appearance  was  more  tertiary  than 
cretaceous.  More  recently,  M.  Heb&rt  having  found  the  Pecten  quadri- 
costatus,  a  cretaceous  species,  in  this  same  pisolitic  rock,  at  Montereau 
near  Paris,  and  some  few  other  fossils  common  to  the  Maestricht  chalk, 
and  to  the  Baculite  limestone  of  the  Cotentin,  in  Normandy,  classed  it  as 
an  upper  member  of  the  cretaceous  group,  an  opinion  since  adopted  by 
M.  Alcide  D'Orbigny,  who  has  carefully  examined  the  fossils.  The 
Nautilus  Danicus  (fig.  249),  and  two  or  three  other  species  found  in  this 
rock,  are  frequent  in  that  of  Faxoe  in  Denmark,  but  as  yet  no  Ammonites, 
Hamites,  Scaphites,  Turrilites,  Baculites,  or  Hippurites  have  been  met 
with.  The  proportion  of  peculiar  species,  many  of  them  of  tertiary  aspect, 
is  confessedly  large ;  and  great  aqueous  erosion  suffered  by  the  white 
chalk,  before  the  pisolitic  limestone  was  found,  affords  an  additional  indi- 
cation of  the  two  deposits  being  widely  separated  in  time.  The  pisolitic 
formation,  therefore,  may  eventually  prove  to  be  somewhat  more  inter- 
mediate in  date  between  the  secondary  and  tertiary  epochs  than  the 
Maestricht  rock. 

It  should  however  be  observed,  that  all  the  "above-mentioned  strata, 
from  the  Thanet  sands  to  the  Pisolitic  limestone  inclusive,  and  even 
the  Maestricht  rock,  next  to  be  described,  exhibit  marks  of  denudation 
experienced  at  various  dates,  subsequently  to  the  consolidation  of  the 
white  chalk.  This  fact  helps  us  in  some  degree  to  explain  the  remark- 
able break  in  the  sequence  of  European  rocks,  between  the  secondary 
and  tertiary  eras,  for  many  strata  which  once  existed  have  doubtless  been 
swept  away. 

CLASSIFICATION    OF    THE    CRETACEOUS   ROCKS. 

The  cretaceous  group  has  generally  been  divided  into  an  Upper  and 
a  Lower  series,  each  of  them  comprising  several  subdivisions,  distin- 
guished by  peculiar  fossils,  and  sometimes  retaining  a  uniform  mineral 
character  throughout  wide  areas.  The  Upper  series  is  often  called  famil- 
iarly the  chalk,  and  the  Lower  the  greensand,  the  last-mentioned  name 
being  derived  from  the  green  color  imparted  to  certain  strata  by  grains 
of  chloritic  matter.  The  following  table  comprises  the  names  of  the  sub 
divisions  most  commonly  adopted  : 

UPPER   CRETACEOUS. 

A.  1.  Maestricht  beds  and  Faxoe  limestones. 

2.  White  chalk  with  flints. 

3.  Chalk  marl,  or  gray  chalk  slightly  argillaceous. 


CH,  XVII]  MAESTRICHT  BEDS.  237 

4.  Upper  greensand,  occasionally  with  beds  of  chert,  and  with  chlovitic  marl 

(craie  chloritee  of  French  authors)  in  the  upper  portion. 

5.  Gault,  including  the  Blackdown  beds. 

LOWER  CRETACEOUS  (or  Neocomian). 

B.  1.  Lower  greensand — Greensand,  Ironsand,  clay,  and  occasional  beds  of  lime- 
stone (Kentish  Rag). 
2.  Wealden  beds  or  Weald  clay  and  Hastings  sands.* 

Maestricht  Beds. — On  the  banks  of  the  Meuse,  at  Maestricht,  reposing 
on  ordinary  white  chalk  with  flints,  we  find  an  upper  calcareous  formation 
about  100  feet  thick,  the  fossils  of  which  are,  on  the  whole,  very  peculiar, 
and  all  distinct  from  tertiary  species.  Some  few  are  of  species  common 
to  the  inferior  white  chalk,  among  which  may  be  mentioned  Belemnites 
mucronatus  (fig.  256,  p.  245)  and  Pecten  quadricostatus,  a  shell  i«- 
garded  by  many  as  a  mere  variety  of  P.  guinqztecostatus  (see  fig.  271). 
Besides  the  Belemnite  there  are  other  genera,  such  as  Baculite  and  Ha- 
mite,  never  found  in  strata  newer  than  the  cretaceous,  but  frequently  met 
with  in  these  Maestricht  beds.  On  the  other  hand,  Voluta,  Fasciolaria, 
and  other  genera  of  univalve  shells,  usually  met  with  only  in  tertiary 
strata,  occur. 

The  upper  part  of  the  rock,  about  20  feet  thick,  as  seen  in  St.  Peter's 
Mount,  in  the  suburbs  of  Maestricht,  abounds  in  corals  and  Bryozoa,  often 
detachable  from  the  matrix ;  and  these  beds  are  succeeded  by  a  soft  yel- 
lowish limestone  50  feet  thick,  extensively  quarried  from  time  immemorial 
for  building.  The  stone  below  is  whiter,  and  contains  occasional  nodules 
of  gray  chert  or  chalcedony. 

M.  Bosquet,  with  whom  I  examined  this  formation  (August,  1850), 
pointed  out  to  me  a  layer  of  chalk  from  2  to  4  inches  thick,  containing 
green  earth  and  numerous  encrinital  stems,  which  forms  the  line  of  de- 
marcation between  the  strata  containing  the  fossils  peculiar  to  Maestricht 
and  the  white  chalk  below.  The  latter  is  distinguished  by  regular  layers 
of  black  flint  in  nodules,  and  by  several  shells,  such  as  Terebratula  earned 
(see  fig.  267),  wholly  wanting  in  beds  higher  than  the  green  band.  Some 
of  the  organic  remains,  however,  for  which  St.  Peter's  Mount  is  cele- 
brated, occur  both  above  and  below  that  parting  layer,  and,  among 
others,  the  great  marine  reptile  called  Mosasaurus  (see  fig.  247),  a  sau- 
rian supposed  to  have  been  24  feet  in  length,  of  which  the  entire  skull 

*  M.  Alcide  D'Orbigny,  in  his  valuable  work  entitled  Paleontologie  Francaise, 
has  adopted  new  terms  for  the  French  subdivisions  of  the  Cretaceous  Series,  which, 
so  far  as  they  can  be  made  to  tally  with  English  equivalents,  seem  explicable  thus  . 

Etage  Danien.          Maestricht  beds. 

Etage  Senonien.       White  chalk,  and  chalk  marl. 

Etage  Turonien.        Part  of  the  chalk  marl. 

Etage  Cenomanien.  Upper  greensand. 

Etage  Albien.  Gault. 

Etage  Aptien.  Upper  part  of  lower  greensand 

Etage  Neocornien.     Lower  part  of  same. 

Etage  Neocornien 

inferieur.  Wealden  beds  and  contemporaneous  marine  strata. 


238  CHALK  OF  FAXOE.  [On.  XVII. 

and  a  great  part  of  the  skeleton  have  been  found.     Such  remains  are 
chiefly   met  with  in  the  soft  freestone,   the  principal   member   of  the 


Fig.  247. 


Mosasaurua  eamperi.    Original  more  than  8  feet  long. 

Maestricht  beds.  Among  the  fossils  common  to  the  Maestricht  and  white 
chalk  ma}7"  be  instanced  the  echinoderm  (fig.  248). 

I  saw  proofs  of  the  previous  denudation  of  the  white  chalk  exhibited 
in  the  lower  bed  of  the  Maestricht  formation  Fig.  248. 

in  Belgium,  about  30  miles  S.  W.  of  Maestricht, 
at  the  village  of  Jendrain,  where  the  base  of 
the  newer  deposit  consisted  chiefly  of  a  layer 
of  well-rolled,  black,  chalk-flint  pebbles,  in  the 
midst  of  which  perfect  specimens  of  Thecidea 
radians  and  Belemnites  mucronatus  are  im- 
bedded, ffemipn&ustes  radiatus,  Ag. 

Chalk  of  Faxoe. — In  the  island  of  Seeland,       Spatangus  radio***  Lam. 

„     ,         ,        '       Chalk  of  Maestricht  and  white 

m  Denmark,  the  newest  member  of  the  chalk  chalk, 

series,  seen  in  the  sea-cliffs  at  Stevensklint  resting  on  white  chalk  with 
flints,  is  a-  yellow  limestone,  a  portion  of  which,  at  Faxoe,  where  it  is 
used  as  a  building-stone,  is  composed  of  corals,  even  more  conspicuously 
than  is  usually  observed  in  recent  coral  reefs.  It  has  been  quarried  to 
the  depth  of  more  than  40  feet,  but  its  thickness  is  unknown.  The  im- 
bedded shells  are  chiefly  casts,  many  of  them  of  univalve  mollusca,  which 
are  usually  very  rare  in  the  white  chalk  of  Europe.  Thus,  there  are  two 
species  of  Cyprcea,  one  of  Oliva,  two  of  Mitra,  four  of  the  genus 
Cerithium,  six  of  Fusus,  two  of  Trochus,  one  Patella,  one  Emarginula, 
&c. ;  on  the  whole,  more  than  thirty  univalves,  spiral  or  patelliform.  At 
the  same  time,  some  of  the  accompanying  bivalve  shells,  echinoderms,  and 
zoophytes  are  specifically  identical  with  fossils  of  the  true  Cretaceous 
series.  Among  the  cephalopoda  of  Faxoe  may  be  mentioned  Bacu- 
lites  Faujasii  and  Belemnites  mucronatus,  shells  of  the  white  chalk. 
The  Nautilus  Danicus  (see  fig.  249)  is  characteristic  of  this  formation  ; 
and  it  also  occurs  in  France  in  the  calcaire  pisolitique  of  Laversin  (dept 
of  Oise). 


CH.  XVII] 


WHITE   CHALK. 
Fig.  249. 


rl 


Nautilus  Danicus,  SchL— Faxoe,  Denmark. 

The  claws  and  entire  skull  of  a  small  crab,  Brachyu- 
rus  rugosus  (Schlottheim),  are  scattered  through  the 
Faxoe  stone,  reminding  us  of  similar  crustaceans  in- 
closed in  the  rocks  of  modern  coral  reefs.-  Some 
small  portions  of  this  coralline  formation  consist  of 
white  earthy  chalk ;  it  is  therefore  clear  that  this  sub- 
stance must  have  been  produced  simultaneously ;  a 
fact  of  some  importance,  as  bearing  on  the  theory  of 
the  origin  of  white  chalk ;  for  the  decomposition  of 
such  corals  as  we  see  at  Faxoe  is  capable,  we  know,  of 
forming  white  mud,  undistinguishable  from  chalk,  and 
which  we  may  suppose  to  have  been  dispersed  far  and 
wide  through  the  ocean,  in  which  such  reefs  as  that  of 
Faxoe  grew. 

White  chalk  (see  Tab.  p.  236,  et  seq.).— The  highest 
beds  of  chalk  in  England  and  France  consist  of  a  pure, 
white,  calcareous  mass,  usually  too  soft  for  a  building- 
stone,  but  sometimes  passing  into  a  more  solid  state.  It 
consists,  almost  purely,  of  carbonate  of  lime ;  the  strati- 
fication is  often  obscure,  except  where  rendered  distinct 
by  interstratified  layers  of  flint,  a  few  inches  thick,  occa- 
sionally in  continuous  beds,  but  oftener  in  nodules,  and 
recurring  at  intervals  from  2  to  4  feet  distant  from 
each  other. 

This  upper  chalk  is  usually  succeeded,  in  the  descend- 
ing order,  by  a  great  mass  of  white  chalk  without  flints, 
below  which  comes  the  chalk  marl,  in  which  there  is  a 
slight  admixture  of  argillaceous  matter.  The  united 
thickness  of  the  three  divisions  in  the  south  of  England 
equals,  in  some  places,  1000  feet. 

The  annexed  section  (fig.  250)  will  show  the  man- 
ner in  which  the  white  chalk  extends  from  England 
into  France,  covered  by  the  tertiary  strata  described 
in  former  chapters,  and  reposing  on  lower  cretaceous 
beds. 


240  ANIMAL   ORIGIN   OF   WHITE   CHALK.  [Cur.  XVII 

Geographical  extent  and  origin  of  the  White  Chalk. — The  area  over 
which  the  white  chalk  preserves  a  nearly  homogeneous  aspect  is  so  vast, 
that  the  earlier  geologists  despaired  of  discovering  any  analogous  de- 
posits of  recent  date.  Pure  chalk,  of  nearly  uniform  aspect  and  compo- 
sition, is  met  with  in  a  northwest  and  southeast  direction,  from  the  north 
of  Ireland  to  the  Crimea,  a  distance  of  about  1140  geographical  miles, 
and  in  an  opposite  direction  it  extends  from  the  south  of  Sweden  to  the 
south  of  Bourdeaux,  a  distance  of  about  840  geographical  miles.  In 
Southern  Russia,  according  to  Sir  R.  Murchison,  it  is  sometimes  600  feet 
thick,  and  retains  the  same  mineral  character  as  in  France  and  England, 
with  the  same  fossils,  including  Inoceramus  Cuvieri,  Belemnites  mucro- 
natus,  and  Ostrea  vesicularis. 

But  it  would  be  an  error  to  imagine  that  the  chalk  was  ever  spread  out 
continuously  over  the  whole  of  the  space  comprised  within  these  limits, 
although  it  prevailed  in  greater  or  less  thickness  over  large  portions  of 
that  area.  On  turning  to  those  regions  of  the  Pacific  where  coral  reefs 
abound,  we  find  some  archipelagoes  of  lagoon  islands,  such  as  that  of 
the  Dangerous  Archipelago,  for  instance,  and  that  of  Radack,  with  sev- 
eral adjoining  groups,  which  are  from  1100  to  1200  miles  in  length, 
and  300  or  400  miles  broad ;  and  the  space  to  which  Flinders  proposed 
to  give  the  name  of  the  Coralline  Sea  is  still  larger ;  for  it  is  bounded 
on  the  east  by  the  Australian  barrier — all  formed  of  coral  rock, — on 
the  west  by  New  Caledonia,  and  on  the  north  by  the  reefs  of  Louisiade. 
Although  the  islands  in  these  areas  may  be  thinly  sown,  the  mud  of 
the  decomposing  zoophytes  may  be  scattered  far  and  wide  by  oceanic 
currents.  That  this  mud  would  resemble  chalk  I  have  already  hinted 
when  speaking  of  the  Faxoe  limestone,  p.  238,  and  it  was  also  remarked 
in  an  early  part  of  this  volume,  that  even  some  of  that  chalk,  which 
appears  to  an  ordinary  observer  quite  destitute  of  organic  remains, 
is  nevertheless,  when  seen  under  the  microscope,  full  of  fragments  of 
corals,  bryozoa,  and  sponges ;  together  with  the  valves  of  entomo- 
straca,  the  shells  of  foraminifera,  and  still  more  minute  infusoria.  (See 
p.  26.) 

Now  it  had  been  often  suspected,  before  these  discoveries,  that  white 
chalk  might  be  of  animal  origin,  even  where  every  trace  of  organic  struc- 
ture has  vanished.  This  bold  idea  was  partly  founded  on  the  fact,  that 
the  chalk  consisted  of  carbonate  of  lime,  such  as  would  result  from  the 
decomposition  of  testacea,  echini,  and  corals ;  and  partly  on  the  passage 
observable  between  these  fossils  when  half  decomposed  and  chalk.  But 
this  conjecture  seemed  to  many  naturalists  quite  vague  and  visionary, 
until  its  probability  was  strengthened  by  new  evidence  brought  to  light 
by  modern  geologists. 

We  learn  from  Capt.  Nelson,  that,  in  the  Bermuda  Islands,  and  in 
the  Bahamas,  there  are  many  basins  or  lagoons  almost  surrounded  and 
inclosed  by  reefs  of  coral.  At  the  bottom  of  these  lagoons  a  soft  white 
calcareous  mud  is  formed,  not  merely  from  the  comminution  of  corallines 
(or  calcareous  plants)  and  corals,  together  with  the  exuviae  of  forarainifera, 


CH.  XVIL]  AXIMAL    ORIGIN   OF   WHITE   CHALK.  241 

mollusks,  echinoderms,  and  crustaceans,  but  also,  as  Mr.  Darwin  observed 
upon  studying  the  coral  islands  of  the  Pacific,  from  the  faecal  matter 
ejected  by  echinoderms,  conchs,  and  coral-eating  fish.  In  the  West 
Indian  seas,  the  conch  (Strombus  gigas)  adds  largely  to  the  chalky  mud 
by  means  of  its  faecal  pellets,  composed  of  minute  grains  of  soft  calca- 
reous matter,  exhibiting  some  organic  tissue.  Mr.  Darwin  describes 
gregarious  fishes  of  the  genus  Scarus,  seen  through  the  clear  waters 
of  the  coral  regions  of  the  Pacific  browsing  quietly  in  great  numbers 
on  living  corals,  like  grazing  herds  of  graminivor- 
ous quadrupeds.  On  opening  their  bodies,  their  rig.  251. 
intestines  were  found  to  be  filled  with  impure 
chalk.  This  circumstance  is  the  more  in  point, 
when  we  recollect  how  the  fossilist  was  formerly 
puzzled  by  meeting,  in  chalk,  with  certain  bodies, 
called  "  larch-cones,"  which  were  afterwards  rec- 
ognized by  Dr.  Buckland  to  be  the  excrement  of 
fish.  Such  spiral  coprolites  (fig.  251),  like  the 
scales  and  bones  of  fossil  fish  in  the  chalk,  are 
composed  chiefly  of  phosphate  of  lime. 

In  the  Bahamas,  the  angel-fish,  and  the  unicorn  or  trumpet-fish,  and 
many  others,  feed  on  shell-fish,  or  on  corals. 

The  mud  derived  from  the  sources  above  mentioned  may  be  actually 
seen  in  the  Maldiva  Atolls  to  be  washed  out  of  the  lagoons  through  nar- 
row openings  leading  from  the  lagoon  to  the  ocean,  and  the  waters  of  the 
sea  are  discolored  by  it  for  some  distance.  When  dried,  this  mud  is  very 
like  common  chalk,  and  might  probably  be  made  by  a  moderate  pressure 
to  resemble  it  more  closely.* 

Mr.  Dana,  when  describing  the  elevated  coral  reef  of  Oahu,  in  the 
Sandwich  Islands,  says  that  some  varieties  of  the  rock  consist  of  aggre- 
gated shells,  imbedded  in  a  compact  calcareous  base  as  firm  in  texture  as 
any  secondary  limestone ;  while  others  are  like  chalk,  having  its  color, 
its  earthy  fracture,  its  soft  homogeneous  texture,  and  being  an  equally  good 
writing  material.  The  same  author  describes,  in  many  growing  coral 
reefs,  a  similar  formation  of  modern  chalk,  undistinguishable  from  the 
ancient.f  The  extension,  over  a  wide  submarine  area,  of  the  calcareous 
matrix  of  the  chalk,  as  well  as  of  the  imbedded  fossils,  would  take  place 
more  readily  in  consequence  of  the  low  specific  gravity  of  the  shells  of 
mollusca  and  zoophytes,  when  compared  with  ordinary  sand  and  mineral 
matter.  The  mud  also  derived  from  their  decomposition  would  be  much 
lighter  than  argillaceous  and  inorganic  mud,  and  very  easily  transported 
by  currents,  especially  in  salt  water. 

Single  pebbles  in  chalk. — The  general  absence  of  sand  and  pebbles  in 
the  white  chalk  has  been  already  mentioned ;  but  the  occurrence  here 
and  there,  in  the  southeast  of  England,  of  a  few  isolated  pebbles  of 

*  See  Nelson,  GeoL  Trans.  1837,  vol.  v.  p.  108  ;  and  GeoL  Quart.  Journ.  1853, 
p.  200. 

f  Geol.  of  IT.  S.  Exploring  Exped.  p.  252,  1849. 

16 


242  PEBBLES  IN  CHALK.  [Ca  XVU 

quartz  and  green  schist,  some  of  them  2  or  3  inches  in  diameter,  has 
justly  excited  much  wonder.  If  these  had  been  carried  to  the  spots 
where  we  now  find  them  by  waves  or  currents  from  the  lands  once 
bordering  the  cretaceous  sea,  how  happened  it  that  no  sand  or  mud 
was  transported  thither  at  the  same  time  ?  We  cannot  conceive  such 
rounded  stones  to  have  been  drifted  like  erratic  blocks  by  ice  (see  ch. 
x.  and  xi.),  for  that  would  imply  a  cold  climate  in  the  Cretaceous  period ; 
a  supposition  inconsistent  with  the  luxuriant  growth  of  large  chambered 
univalves,  numerous  corals,  and  many  fish,  and  other  fossils  of  tropical 
forms. 

Now  in  Keeling  Island,  one  of  those  detached  masses  of  coral  which 
rise  up  in  the  wide  Pacific,  Captain  Ross  found  a  single  fragtaent  of  green- 
stone, where  every  other  particle  of  matter  was  calcareous  ;  and  Mr.  Dar- 
win concludes,  that  it  must  have  come  there  entangled  in  the  roots  of  a 
large  tree.  He  reminds  us  that  Chamisso,  the  distinguished  naturalist 
who  accompanied  Kotzebue,  affirms,  that  the  inhabitants  of  the  Radack 
archipelago,  a  group  of  lagoon  islands  in  the  midst  of  the  Pacific,  ob- 
tained stones  for  sharpening  their  instruments  by  searching  the  foots  of 
trees  which  are  cast  up  on  the  beach.* 

It  may  perhaps  be  objected,  that  a  similar  mode  of  transport  cannot 
have  happened  in  the  cretaceous  sea,  because  fossil  wood  is  very  rare  in 
the  chalk.  Nevertheless  wood  is  sometimes  met  with,  and  in  the  same 
parts  of  the  chalk  where  the  pebbles  are  found,  both  in  soft  stone  and  in 
a  silicified  state  in  flints.  In  these  cases  it  has  often  every  appearance  of 
having  been  floated  from  a  distance,  being  usually  perforated  by  boring- 
shells,  such  as  the  Teredo  and  Fistulana.\ 

The  only  other  mode  of  transport  which  suggests  itself  is  sea-weed. 
Dr.  Beck  informs  me  that  in  the  Lym-Fiord,  in  Jutland,  the  Fucus 
vesiculosus,  often  called  kelp,  sometimes  grows  to  the  height  of  10  feet, 
and  the  branches  rising  from  a  single  root  form  a  cluster  several  feet  in 
diameter.  When  the  bladders  are  distended,  the  plant  becomes  so  buoy- 
ant as  to  float  up  loose  stones  several  inches  in  diameter,  and  these  are 
often  thrown  by  the  waves  high  up  on  the  beach.  The  Fucus  giganteus 
of  Solander,  so  common  in  Terra  del  Fuego,  is  said  by  Captain  Cook  to 
attain  the  length  of  360  feet,  although  the  stem  is  not  much  thicker  than 
a  man's  thumb.  It  is  often  met  with  floating  at  sea,  with  shells  attached, 
several  hundred  miles  from  the  spots  where  it  grew.  Some  of  these 
plants,  says  Mr.  Darwin,  were  found  adhering  to  large  loose  stones  in  the 
inland  channels  of  Terra  del  Fuego,  during  the  voyage  of  the  Beagle  in 
1834  ;  and  that  so  firmly,  that  the  stones  were  drawn  up  from  the  bottom 
into  the  boat,  although  so  heavy  that  they  could  scarcely  be  lifted  in  by 
one  person.  Some  fossil  sea-weeds  have  been  found  in  the  Cretaceous 
formation,  but  none,  as  yet,  of  large  size. 

But  we  must  not  imagine  that  because  pebbles  are  so  rare  in  the  white 

*  Darwin,  p.  549.     Kotzebue's  First  Voyage,  vol.  iii.  p.  155. 
f  Mantell,  Geol.  of  S.  E.  of  England,  p.  96. 


Cn.  XVII.]  CHALK  FLINTS.  243 

chalk  of  England  and  France  there  are  no  proofs  of  sand,  shingle,  and 
clay  having  been  accumulated  contemporaneously  even  in  European  seas. 
The  siliceous  sandstone,  called  "  upper  quader"  by  the  Germans,  overlies 
white  argillaceous  chalk  or  "  planer-kalk,"  a  deposit  resembling  in  com- 
position and  organic  remains  the  chalk  marl  of  the  English  series.  This 
sandstone  contains  as  many  fossil  shells  common  to  our  white  chalk  as 
could  be  expected  in  a  sea-bottom  formed  of  such  different  materials.  It 
sometimes  attains  a  thickness  of  600  feet,  and  by  its  jointed  structure  and 
vertical  precipices,  plays  a  conspicuous  part  in  the  picturesque  scenery  of 
Saxon  Switzerland,  near  Dresden. 

Chalk  Flints. — The  origin  of  the  layers  of  flint,  whether  in  continuous 
sheets  or  in  the  form  of  nodules,  is  more  difficult  to  explain  than  is  that 
of  the  white  chalk.  No  such  siliceous  masses  are  as  yet  known  to  ac- 
company the  aggregation  of  chalky  mud  in  modern  coral  reefs.  The 
flint  abounds  mostly  in  the  uppermost  chalk,  and  becomes  more  rare  or 
is  entirely  wanting  as  we  descend ;  but  this  rule  does  not  hold  universally 
throughout  Europe.  Some  portion  of  the  flint  may  have  been  derived 
from  the  decomposition  of  sponges  and  other  zoophytes  provided  with 
siliceous  skeletons ;  for  it  is  a  fact,  that  siliceous  spiculae,  or  the  minute 
bones  of  sponges,  are  often  met  with  in  flinty  nodules,  and  may  have 
served  at  least  as  points  of  attraction  to  some  of  the  siliceous  matter  when 
it  was  in  the  act  of  separating  from  chalky  mud  during  the  process  of 
solidification.  But  there  are  other  copious  sources  before  alluded  to, 
whence  the  waters  of  the  ocean  derive  a  constant  supply  of  silex  in  solu- 
tion, such  as  the  decomposition  of  felspathic  rock  (see  p.  42),  also  min- 
eral springs  rising  up  in  the  bed  of  the  sea,  especially  those  of  a  high 
temperature  ;  since  their  waters,  if  chilled  when  first  mingling  with  the 
sea,  would  readily  precipitate  siliceous  matter  (see  above,  p.  42).  Never- 
theless, the  occurrence  in  the  white  chalk  of  beds  of  nodular  or  tabular 
flint  at  so  many  distinct  levels,  implies  a  periodical  action  throughout 
wide  oceanic  areas  not  easily  accounted  for.  It  seems  as  if  there  had 
been  time  for  each  successive  accumulation  of  calcareo-siliceous  mud  to 
become  partially  consolidated,  and  for  a  rearrangement  of  its  particles 
to  take  place  (the  heavier  silex  sinking  to  the  bottom)  before  the  next 
stratum  was  superimposed  ;  a  process  formerly  suggested  by  Dr.  Buck- 
land* 

A  more  difficult  enigma  is  presented  by  the  occurrence  of  certain  huge 
flints,  or  potstones  as  they  are  called  in  Norfolk,  occurring  singly,  or 
arranged  in  nearly  continuous  columns  at  right  angles  to  the  ordinary 
and  horizontal  layers  of  small  flints.  I  visited,  in  the  year  1825,  an 
extensive  range  of  quarries  then  open  on  the  river  Bure,  near  Horstead, 
about  six  miles  from  Norwich,  which  afforded  a  continuous  section,  a 
quarter  of  a  mile  in  length,  of  white  chalk,  exposed  to  the  depth  of  26 
feet,  and  covered  by  a  thick  bed  of  gravel.  The  potstones,  many  of  them 
pear- shaped,  were  usually  about  three  feet  in  height,  and  one  foot  in  their 

*  Geol.  Trans.,  First  series,  vol.  iv.  p.  413. 


244: 


POTSTONES   AT  HORSTEAD. 


[On.  XVII 


transverse  diameter,  placed  in  vertical  rows,  like  pillars  at  irregular  dis- 
tances from  each  other,  but  usually  from  20  to  30  feet  apart,  though  some- 


Fig.  252. 


From  a  drawing  by  Mrs.  Gunn. 
Yiew  of  a  chalk.pit  at  Horstead,  near  Norwich,  showing  the  position  of  the  potstones. 

times  nearer  together,  as  in  the  above  sketch.  These  rows  did  not  ter- 
minate downwards,  in  any  instance  which  I  could  examine,  nor  upwards, 
except  at  the  point  where  they  were  cut  off  abruptly  by  the  bed  of 
gravel.  On  breaking  open  the  potstones,  I  found  an  internal  cylindrical 
nucleus  of  pure  chalk,  much  harder  than  the  ordinary  surrounding  chalk, 
and  not  crumbling  to  pieces  like  it,  when  exposed  to  the  winter's  frost. 
At  the  distance  of  half  a  mile,  the  vertical  piles  of  potstones  were  much 
farther  apart  from  each  other.  Dr.  Buckland  has  described  very  similar 
phenomena  as  characterizing  the  white  chalk  on  the  north  coast  of  An- 
trim, in  Ireland.* 

FOSSILS  OF  THE  UPPER  CRETACEOUS  ROCKS. 

Among  the  fossils  of  the  white  chalk,  echinoderms  are  very  numerous ; 

Fig.  258. 

I 

tt. 


Ananchytes  ovatus.    White  chalk,  upper  and  lower. 
a.  Side  view. 

I.  Bottom  of  the  shell  on  which,  both  the  oral  and  anal  apertures  arc  placed ; 
the  anal  being  more  round,  and  at  the  smaller  end. 

*  Geol.  Trans.,  First  series,  vol.  iv.  p.  413,  "On  Paramoudra,"  &c. 


Cs.  XVII.]       FOSSILS  OF   UPPER   CRETACEOUS  ROCKS. 


245 


and  some  of  the  genera,  like  Ananchytes  (see  fig.  253),  are  exclusively 
cretaceous.     Among  the  Ciinoidea,  the  Marsupite  (fig.  260)  is  a  charac- 


Fig.254 


Fig.  255. 


Micr  aster  cor-anguinum. 
White  chalk. 


GdUrites  aXbogalerus.  Lam. 
White  chalk. 


teristic  genus.  Among  the  mollusca,  the  cephalopoda,  or  chambered 
univalves,  of  the  genera  Ammonite,  Scaphite,  Belemnite  (fig.  256),  Bacu- 
lite  (257-259),  and  Tumlite  (262,  263),  with  other  allied  forms,  present 
a  great  contrast  to  the  testacea  of  the  same  class  in  the  tertiary  and  recent 
periods. 


Fig.  256. 


a.  Bdemnites  mucronatus. 

b.  Same,  showing  internal  structure.    Maastricht,  Faxoe,  and  white  chalk. 


Baculites  anceps.    Upper  grcensand,  or  chloritic  marl,  crate  chloritee.    France 
A.  D'Orb.  Terr.  Cret 


Fig.  25S. 


Fig.  259. 


Portion  ofBootilitss  Faujasii. 

Maestricht  and  Faxoe  beds  and  white  chalk, 

Fig.  260. 


Marsupites  Mitteri. 
White  chalk. 


Portion  of  Baculites  anceps. 
Maestricht  and  Faxoe  beds  and  white  chalk. 

Fig.  261. 


Scaphites  aquali*.    Chloritio 

marl  of  Upper  Greensand, 

Dorsetshire. 


246 


FOSSILS   OF   UPPER   CRETACEOUS  ROCKS.        [Cu.  XVtt 
Fig.  262.  Fig.  263. 


a.  Fragment  of  Turrilites  costatus. 
Chalk  marl. 


Turrilites  costatus, 
Chalk. 


0.  Same,  showing  the  indented  border 
of  the  partition  of  the  chambers. 


Among  the   brachiopoda  in  the  white  chalk,  the  Terebratulce  are  very 
abundant.    These  shells  are  known  to  live  at  the  bottom  of  the  sea,  where 


Fig.  264. 


Fig.  265. 


Fig.  267. 


Terebratula  Defrancii. 
Upper  white  chalk. 


Terebratula 

octoplicata. 

(Var.  of  T.  plioatilis.) 

Upper  white  chalk. 


Terebratula  pumilus,         Terebratula 
(Magas  purmlm,  Sow.)  carnea. 

Upper  white  chalk.      Upper  white  chalk. 


the  water  is  tranquil  and  of  some  depth  (see  figs.  264,  265,  266,  267, 
268).  With  these  are  associated  some  forms  of  oyster  (see  figs.  275, 
276,  277),  and  other  bivalves  (figs.  269,  270,  271,  272,  273). 


Fig.  268. 


Fig.  269. 


Fig.  2TO. 


Terebratula  ftiplicata, 
Bow.    Upper  cretaceous. 


Crania  Parisiensis, 
inferior  or  attached 

valve. 
Upper  white  chalk. 


Pecten  Seaveri,  reduced  to 

one-third  diameter. 
Lower  white  chalk  and  chalk 
marl.    Maidstone. 


Among  the  bivalve  mollusca,  no  form  marks  the  cretaceous  era  in 
Europe,  America,  and  India  in  a  more  striking  manner  than  the 
extinct  genus  Inoceramus  (Catillus  of  Lam.;  see  fig.  274),  the  shells 


CK.  XVIL]       FOSSILS   OF   UPPEK   CKETACEOUS  ROCKS. 


247 


of  which  are  distinguished  by  a  fibrous  texture,  and  are  often  met  with  in 
fragments,  having  probably  been  extremely  friable. 


Fig.  271. 


Fig.  272. 


Fig.  273. 


Pecten  5-costatvs. 
White  chalk,  upper  and 
lower  greensands. 


Plagiostoma  Hoperi,  Sow. 

Syn.  Lima  Boperi. 

"White  chalk  and  upper 

greensand. 


Plagiostoma  spinosum,  Sow. 
Syn.  Spondylus  spinosus. 
Upper  white  chalk. 


Of  the  singular  family  called  Rudistes,  by  Lamarck,  hereafter  to  be 
mentioned  as  extremely  characteristic  of  the  chalk  of  Southern  Europe,  a 


Fig.  274 


Fig.  275. 


Jnoceramus  Lamarckii. 

Syn.  Catillus  Lamarckii. 

White  chalk  (Bixon's  Geol.  Sussex,  Tab.  23, 

fig.  29). 


Ostrea  veticularis.    Syn.  GrypTicea  globosa. 
Upper  chalk  and  upper  greensand. 


single  representative  only  (fig.  278)  has  been  discovered  in  the  white 
chalk  of  England. 


Fig.  276. 


Ostrea  columba. 

Syn.  Gryphcea  columba. 

Upper  greensand. 


Fig.  2T7. 


Ostrea  carinata.    Chalk  marl,  upper  and 
lower  greensand. 


248 


MOLLUSCA,  BKYOZOA,   SPONGES. 
Fig.  279. 


[Cu.  XVII 


Jiadiolites  Mortoni,  Mantell.    Houghton,  Sussex.    White  chalk. 
Diameter  one-seventh  nat.  size. 

Fig.  278.  Two  individuals  deprived  of  their  upper  valves,  adhering  together. 

279.  Same  seen  from  above. 

280.  Transverse  section  of  part  of  the  wall  of  the  shell,  magnified  to  show  the  s'.tuctuie. 

281.  Vertical  section  of  the  same. 

On  the  side  where  the  shell  is  thinnest,  there  is  one  external  furrow  and  corresponding  internal 
ridge,  #,  &,  figs.  278,  279 ;  but  they  are  usually  less  prominent  than  in  these  figures.  This  species 
was  first  referred  by  Mantell  to  Hippurites,  afterwards  to  the  genus  Hadiolites.  I  have  never 
seen  the  upper  valve.  The  specimen  above  figured  was  discovered  by  the  late  Mr.  Dixon. 

With  these  mollusca  are  associated  many  Bryozoa,  such  as  Eschara 
and  JEscharina  (figs.  282,  283),  which  are   alike  marine,  and,  for  the 


Fig.  282. 


EscJiarina  oceani. 

a.  Natural  size. 

b.  Part  of  the  same  magnified. 

chalk. 


Eschara  disticha. 

a.  Natural  size. 

&.  Portion  magnified. 

White  chalk. 


VentriculUes  radiatus. 

Mantell. 

Syn.  Ocellaria  radiata, 
D'Orb.    White  chalk. 


most  part,  indicative  of  a  deep  sea.    These  and  other  organic  bodies,  es- 
pecially sponges,  such  as  VentriculUes  (fig.  284)  and  Siphonia  (fig.  286). 


CH.  XVIL]    FOSSILS   OF  THE    UPPER  CRETACEOUS  BEDS. 


249 


are  dispersed  indifferently  through  the  soft  chalk  and  hard  flint,  and  some 
of  the  flinty  nodules  owe  their  irregular  forms  to  inclosed  sponges,  such  as 
fig.  285  ct,  where  the  hollows  in  the  exterior  are  caused  by  the  branches 
of  a  sponge,  seen  on  breaking  open  the  flint  (fig.  285  6). 


Fig.  286. 


Fig.  285. 


A  branching  sponge  in  a  flint,  from  the  white  chalk. 
From  the  collection  of  Mr.  Bowerbank. 


Siphonia  pyri- 
formif, 

Chalk  marl 


The  remains  of  fishes  of  the  Upper  Cretaceous  formations  consist 
chiefly  of  teeth  of  the  shark  family,  of  genera  in  part  common  to  the 


Fig.  287. 


Palatal  tooth  of 

Ptychodua  decurrens. 

Lower  white  chalk. 

Maidstone. 


Cestracion.  Phillippi  ;  recent 
Port  Jackson.    Buckland,  Bridgewater  Treatise,  pi.  27,  d. 


tertiary,  and  partly  distinct.     To  the  latter  belongs  the  genus  Ptychodus 
(fig.  287),  which  is  allied  to  the  living  Port  Jackson  Shark,  Oestracion 


250  UPPER  GREENSAND.  [Cn.  XVII 

Pktttippi,  the  anterior  teeth  of  which  (see  fig.  288  a)  are  sharp  and  cut 
ting,  while  the  posterior  or  palatal  teeth  (b).  are  flat,  and  analogous  to 
the  fossil  (fig.  287). 

But  we  meet  with  no  bones  of  land  animals,  nor  any  terrestrial  or 
fluviatile  shells,  nor  any  plants,  except  sea-weeds,  and  here  and  there  a 
piece  of  drift  wood.  All  the  appearances  concur  in  leading  us  to  con- 
clude that  the  white  chalk  was  the  product  of  an  open  sea  of  considerable 
depth. 

The  existence  of  turtles  and  oviparous  saurians,  and  of  a  Pterodactyl  or 
winged  lizard,  found  in  the  white  chalk  of  Maidstone,  implies,  no  doubt, 
some  neighboring  land  ;  but  a  few  small  islets  in  mid-ocean,  like  Ascen- 
sion, formerly  so  much  frequented  by  migratory  droves  of  turtle,  might 
perhaps  have  afforded  the  required  retreat  where  these  creatures  laid  their 
eggs  in  the-  sand,  or  from  which  the  flying  species  may  have  been  blown 
out  to  sea.  Of  the  vegetation  of  such  islands  we  have  scarcely  any  in- 
dication, but  it  consisted  partly  of  cycadeous  plants ;  for  a  fragment  of 
one  of  these  was  found  by  Capt.  Ibbetson  in  the  chalk  marl  of  the  Isle  of 
Wight,  and  is  referred  by  A.  Brongniart  to  Clathraria  Lyellii,  Man  tell,  a 
species  common  to  the  antecedent  Wealden  period. 

The  Pterodactyl  of  the  Kentish  chalk,  above  alluded  to,  was  of  gigantic 
dimensions,  measuring  16  feet  6  inches  from  tip  to  tip  of  its  outstretched 
wings.  Some  of  its  elongated  bones  were  at  first  mistaken  by  able  anat- 
omists for  those  of  birds ;  of  which  class  no  osseous  remains  seern  as  yet 
to  have  been  derived  from  the  chalk,  or  indeed  from  any  secondary  or 
primary  formation,  except  perhaps  the  Wealden. 

Upper  greensand  (Table,  p.  105,  &c.) — The  lower  chalk  without  flints 
passes  gradually  downwards,  in  the  south  of  England,  into  an  argillaceous 
limestone,  "  the  chalk  marl,"  already  alluded  to,  in  which  ammonites  and 
other  cephalopoda,  so  rare  in  the  higher  parts  of  the  series,  appear.  This 
marly  deposit  passes  in  its  turn  into  beds  called  the  Upper  Greensand, 
containing  green  particles  of  sand  of  a  chloritic  mineral.  In  parts  of 
Surrey,  calcareous  matter  is  largely  intermixed,  forming  a  stone  called 
firestone.  In  the  cliffs  of  the  southern  coast  of  the  Isle  of  Wight,  this 
upper  greensand  is  100  feet  thick,  and  contains  bands  of  siliceous  lime- 
stone and  calcareous  sandstone  with  nodules  of  chert. 

The  Upper  Greensand  is  regarded  by  Mr.  Austen  and  Mr.  D.  Sharpe, 
as  a  littoral  deposit  of  the  Chalk  Ocean,  and,  therefore,  contemporane- 
ous with  part  of  the  chalk  marl,  and  even,  perhaps,  with  some  part 
of  the  white  chalk.  For  as  the  land  went  on  sinking,  and  the  cretace- 
ous sea  widened  its.  area,  white  mud  and  chloritic  sand  were  always 
forming  somewhere,  but  the  line  of  sea-shore  was  perpetually  varying 
its  position.  Hence,  though  both  sand  and  mud  originated  simultane- 
ously, the  one  near  the  land,  the  other  far  from  it,  the  san.ds  in  every 
locality  where  a  shore  became  submerged,  might  constitute  the  under- 
lying deposit. 

Gault. — The  lowest  member  of  the  upper  Cretaceous  group,  usually 
about  100  feet  thick  in  the  S.  E.  of  England,  is  provincially  termed 


CH.  XVIL] 


THE    BLACKDOWN  BEDS. 


251 


Gault.    It  consists  of  a  dark  blue  rnarl,  sometimes  intermixed  with  green- 
sand.    Many  peculiar  forms  of  cephalopoda,  such  as  the  Hamite  (fig.  291) 


Fossils  of  the  Upper  Greenland. 
Fig.  289. 


Fig.  290. 


a.  Terebratiila  lyra.      )  Upper  Greensand. 
7*  Same,  seen  in  profile.  J     France. 

IfettL 


Ammonites  Rhotomagentis. 
Upper  Greensand. 


Hamites  spiniger  (Fitton) ;  near  Folkstone.    Gault. 

and  Scaphite,  with  other  fossils,  characterize  this  formation,  which,  small 
as  is  its  thickness,  can  be  traced  by  its  organic  remains  to  distant  parts  of 
Europe,  as,  for  example,  to  the  Alps. 

The  Blackdown  beds  in  Dorsetshire,  celebrated  for  containing  many 
species  of  fossils  not  found  elsewhere,  have  been  commonly  referred  to  the 
Upper  Greensand,  which  they  resemble  in  mineral  character ;  but  Mr. 
Sharpe  has  suggested,  and  apparently  with  reason,  that  they  are  rather 
the  equivalent  of  the  Gault,  and  were  probably  formed  on  the  shore  of 
the  sea,  in  the  deeper  parts  of  which  the  fine  mud  called  Gault  was  de- 
posited. Several  Blackdown  species  are  common  to  the  Lower  cretaceous 
series,  as,  for  example,  Trigonia  caudata,  fig.  299.  We  learn  from  M. 
D'Archiac,  that  in  France,  at  Mons,  in  the  valley  of  the  Loire,  strata  of 
greensand  occur  of  the  same  age  as  the  Blackdown  beds,  and  containing 
many  of  the  same  fossils.  They  are  also  regarded  as  of  littoral  origin  by 
M.  D'Archiac  * 

The  phosphate  of  lime,  found  near  Farnham,  in  Surrey,  in  such  abun- 
dance as  to  be  used  largely  by  the  agriculturist  for  fertilizing  soils,  occurs 
exclusively,  according  to  Mr.  R.  A.  C.  Austen,  in  the  upper  greensand 
and  gault.  It  is  doubtless  of  animal  origin,  and  partly  coprolitic,  prob- 
ably derived  from  the  excrement  of  fish. 

*  Hist,  des  Progres  de  la  Geol.,  <fec.,  vol.  iv.  p.  360,  1851. 


HIPPURITE   LIMESTONE. 


[On.  XVIL 


Fig.  292. 


HIPPURITE    LIMESTONE. 

Difference  between  the  chalk  of  the  north  and  south  of  Europe. — Bj 
the  aid  of  the  three  tests  of  relative  age,  namely,  superposition,  mineral 
character,  and  fossils,  the  geologist  has  been  enabled  to  refer  to  the  same 
Cretaceous  period  certain  rocks  in  the  north  and  south  of  Europe,  which 
differ  greatly,  both  in  their  fossil  contents  and  in  their  mineral  composition 
and  structure. 

If  we  attempt  to  trace  the  cretaceous  deposits  from  England  and 
France  to  the  countries  bordering  the  Mediterranean,  we  perceive,  in  the 
first  place,  that  the  chalk  and  greensand  in  the  neighborhood  of  London 
and  Paris  form  one  great  continuous  mass,  the  Straits  of  Dover  being  a 
trifling  interruption,  a  mere  valley  with  chalk  cliffs  on  both  sides.  We 
then  observe  that  the  main  body  of  the  chalk  which  surrounds  Paris 
stretches  from  Tours  to  near  Poitiers  (see  the  annexed  map,  fig.  292,  in 
which  the  shaded  part  represents  chalk). 

Between  Poitiers  and  La  Rochelle,  the 
space  marked  A  on  the  map  separates  two 
regions  of  chalk.  This  space  is  occupied  by 
the  Oolite  and  certain  other  formations  older 
than  the  Chalk,  and  has  been  supposed  by 
M.  E.  de  Beaumont  to  have  formed  an 
island  in  the  cretaceous  sea.  South  of  this 
space  we  again  meet  with  a  formation 
which  we  at  once  recognize  by  its  mineral 
character  to  be  chalk,  although  there  are 
some  places  where  the  rock  becomes 
oolitic.  The  fossils  are,  upon  the  whole, 
very  similar ;  especially  certain  species  of 
the  genera  Spatangus,  Ananchytes,  Cida- 
rites,  Nucula,  Ostrea,  Gryphcea  (Exogyra), 
Pecten,  Plagiostoma  (Lima),  Trigonia, 
Catillus  (Inoceramus),  and  Terebratula.* 
But  Ammonites,  as  M.  d'Archiac  observes, 
of  which  so  many  species  are  met  with  in 
the  chalk  of  the  north  of  France,  are  scarcely  ever  found  in  the  southern 
region ;  while  the  genera  Hamite,  Turrilite,  and  Scaphite,  and  perhaps 
Belemnite,  are  entirely  wanting. 

On  the  other  hand,  certain  forms  are  common  in  the  south  which  are 
rare  or  wholly  unknown  in  the  north  of  France.  Among  these  may  be 
mentioned  many  Hippurites,  Sphcerulites,  and  other  members  of  that 
great  family  of  mollusca  called  Rudistes  by  Lamarck,  to  which  nothing 
analogous  has  been  discovered  in  the  living  creation,  but  which  is 
quite  characteristic  of  rocks  of  the  Cretaceous  era  in  the  south  of 


*  D'Archiac,  stir  la  Form.  Cre'tace'e  du  S.  0.  de  la  France,  Mem.  de  la  Soc.  Ge"oL 
\e  France,  torn.  ii. 


CH.  XVIL] 


CHALK   OF   SOUTH   OF   EUROPE. 


253 


France,  Spain,  Sicily,  Greece,  and  other  countries  bordering  the  Mediter- 
ranean. 


Fig.  293. 


Fig.  294. 


a.  Radiolitfs  radiosrts,  D'Orb.    (Hippurites,  Lam.) 
/>.  Upper  valve  of  same. 

"White  chalk  of  France. 


Fig.  295. 


BadioliteafoUaceus,  D'Orb. 
Syn.  Sphcerulites  agarici- 

formis,  Blainv. 
White  chalk  of  France. 


Hippurite$  organisans,  Desmoulins. 

Upper  chalk :— chalk  marl  of  Pyrenees?* 

a.  Young  individual ;  when  full  grown  they  occur  in  groups  adhering 

laterally  to  each  other. 

5.  Upper  Bide  of  the  upper  valve,  showing  a  reticulated  structure  in 
those  parts,  6,  where  the  external  coating  is  worn  off. 

c.  Upper  end  or  opening  of  the  lower  and  cylindrical  valve. 

d.  Cast  of  the  interior  of  the  lower  conical  valve. 

The  species  called  Hippurites  organisans  (fig.  295)  is  more  abundant 
than  any  other  in  the  south  of  Europe  ;  and  the  geologist  should  make- 
himself  well  acquainted  with  the  cast  <?,  which  is  far  more  common  in 
many  compact  marbles  of  the  upper  cretaceous  period  than  the  shell 
itself  this  having  often  wholly  disappeared.  The  flutings,  or  smooth, 
rounded,  longitudinal  ribs,  representing  the  form  of  the  interior,  are  wholly 
unlike  the  Hippurite  itself  and  in  some  individuals  attain  a  great  size  and 
'.ength. 

Between  the  region  of  chalk  last  mentioned,  in  which  Perigueux  is 


D'Orbigny's  PalSontologie  Franchise,  pi.  533. 


254:  CRETACEOUS  ROCKS.  [Cn.  XVII 

situated,  and  the  Pyrenees,  the  space  B  intervenes.  (See  Map,  fig.  292.) 
Here  the  tertiary  strata  cover,  and  for  the  most  part  conceal,  the  cre- 
taceous rocks,  except  in  some  spots  where  they  have  been  laid  open  by  the 
denudation  of  the  newer  formations.  In  these  places  they  are  seen  still 
preserving  the  form  of  a  white  chalky  rock,  which  is  charged  in  part  with 
grains  of  greensand.  Even  as  far  south  as  Tercis,  on  the  Adour,  near 
Dax,  cretaceous  rocks  retain  this  character  where  I  examined  them  in 
1828,  and  where  M.  Grateloup  has  found  in  them  Ananchytes  ovata 
(fig.  253),  and  other  fossils  of  the  English  chalk,  together  with  Hippurites. 

CRETACEOUS    ROCKS    IN    THE    UNITED    STATES. 

If  we  pass  to  the  American  continent,  we  find  in  the  State  of  New 
Jersey  a  series  of  sandy  and  argillaceous  beds  wholly  unlike  our  Upper 
Cretaceous  system ;  which  we  can,  nevertheless,  recognize  as  referable, 
paleontologically,  to  the  same  division. 

Thf.t  they  were  about  the  same  age  generally  as  the  European  chalk 
and  greensand,  was  the  conclusion  to  which  Dr.  Morton  and  Mr.  Conrad 
came  after  their  investigation  of  the  fossils  in  1834.  The  strata  consist 
chiefly  of  greensand  and  green  marl,  with  an  overlying  coralline  limestone 
of  a  pale  yellow  color,  and  the  fossils,  on  the  whole,  agree  most  nearly 
with  those  of  the  upper  European  series,  from  the  Maestricht  beds  to  the 
gault  inclusive.  I  collected  sixty  shells  from  the  New  Jersey  deposits  in 
1841,  five  of  which  were  identical  with  European  species — Ostrea  larva, 
0.  vesicularis,  Gryphcea  costata,  Pecten  quinque-costatus,  Belemnites 
mucronatus.  As  some  of  these  have  the  greatest  vertical  range  in  Europe, 
they  might  be  expected  more  than  any  others  to  recur  in  distant  parts  of 
the  globe.  Even  where  the  species  are  different,  the  generic  forms,  such 
as  the  Baculite  and  certain  sections  of  Ammonites,  as  also  the  Inocera- 
mus  (see  above,  fig.  274)  and  other  bivalves,  have  a  decidedly  cretaceous 
aspect.  Fifteen  out  of  the  sixty  shells  above  alluded  to  were  regarded 
by  Professor  Forbes  as  good  geographical  representatives  of  well-known 
cretaceous  fossils  of  Europe.  The  correspondence,  therefore,  is  not  small, 
when  we  reflect  that  the  part  of  the  United  States  where  these  strata 
occur  is  between  3000  and  4000  miles  distant  from  the  chalk  of  Central 
and  Northern  Europe,  and  that  there  is  a  difference  of  ten  degrees  in  the 
latitude  of  the  places  compared  on  opposite  sides  of  the  Atlantic.* 

Fish  of  the  genera  Lamna,  Galeus,  and  Carcharodon  are  common  to 
New  Jersey  and  the  European  cretaceous  rocks.  So  also  is  the  genus 
Mosasaurus  among  reptiles.  The  vertebra  of  a  Plesiosaurus,  a  reptile 
known  in  the  English  chalk,  had  often  been  cited  on  the  authority  of 
Dr.  Harlan  as  occurring  in  the  cretaceous  marl,  at  Mullica  Hill,  in  New 
Jersey.  But  Dr.  Leidy  has  since  shown  that  the  bone  in  question  is  not 
saurian  but  cetaceous,  and  whether  it  can  truly  lay  claim  to  the  high 
antiquity  assigned  to  it,  is  a  point  still  open  to  discussion.  The  discovery 
of  another  mammal  of  the  seal  tribe  (Stenorhynchus  vetus,  Leidy),  from 

*  See  a  paper  by  the  author,  Quart.  Journ.  Geol.  See.  vol.  i.  p.  79. 


Ca  XVIL]  CRETACEOUS  ROCKS.  255 

a  lower  bed  in  the  cretaceous  series  in  New  Jersey,  appears  to  rest  on 
better  evidence.* 

From  New  Jersey  the  cretaceous  formation  extends  southwards  to  North 
Carolina  and  Georgia,  cropping  out  at  intervals  from  beneath  the  tertiary 
strata,  between  the  Appalachian  Mountains  and  the  Atlantic.  They  then 
sweep  round  the  southern  extremity  of  that  chain,  in  Alabama  and  Mis- 
sissippi, and  stretch  northwards  again  to  Tennessee  and  Kentucky.  They 
have  also  been  traced  far  up  the  valley  of  the  Missouri,  as  far  north  as  lat. 
48°,  or  to  Fort  Mandan  ;  so  that  already  the  area  which  they  are  ascer- 
tained to  occupy  in  North  America  may  perhaps  equal  their  extent  in 
Europe,  and  exceeds  that  of  any  other  fossiliferous  formation  in  the  United 
States.  So  little  do  they  resemble  mineralogically  the  European  white 
chalk,  that  in  North  America,  limestone  is  upon  the  whole  an  exception 
to  the  rule  ;  and  even  in  Alabama,  where  I  saw  a  calcareous  member  of 
this  group,  composed  of  marl-stone,  it  was  more  like  the  English  and 
French  Lias  than  any  other  European  secondary  deposit. 

At  the  base  of  the  system  in  Alabama,  I  found  dense  masses  of  shingle, 
perfectly  loose  and  unconsolidated,  derived  from  the  waste  of  paleozoic  (or 
carboniferous)  rocks,  a  mass  in  no  way  distinguishable,  except  by  its  position, 
from  ordinary  alluvium,  but  covered  with  marls  abounding  in  Inocerami. 

In  Texas,  according  to  F.  Eomer,  the  chalk  assumes  a  new  lithological 
type,  a  large  portion  of  it  consisting  of  hard  siliceous  limestone,  but  the 
organic  remains  leave  no  doubt  in  regard  to  its  age,  the  Baculites  anceps 
and  ten  other  European  species  occurring  there. 

In  South  America  the  cretaceous  strata  have  been  discovered  in  Colum- 
bia, as  at  Bogota,  and  elsewhere,  containing  Ammonites,  Hamites,  Inoce- 
rami, and  other  characteristic  shells.f 

In  the  south  of  India,  also,  at  Pondicherry,  Verdachellum,  and  Trin- 
conopoly,  Messrs.  Kaye  and  Egerton  have  collected  fossils  belonging 
to  the  cretaceous  system.  Taken  in  connection  with  those  from  the 
United  States,  they  prove,  says  Professor  E.  Forbes,  that  those  powerful 
causes  which  stamped  a  peculiar  character  on  the  forms  of  marine  animal 

*  In  the  Principles  of  Geology,  ninth  ed.  p.  145,  I  cited  Dr.  Leidy,  of  Philadel- 
phia, as  having  described  (Proceedings  of  Acad.  Nat.  Sci.  Philad.  1851)  two 
species  of  cetacea  of  a  new  genus  which  he  called  Priscodelphinus,  from  the 
greensand  of  New  Jersey.  In  1853, 1  saw  the  two  vertebrae  at  Philadelphia, 
on  which  this  new  genus  was  founded,  and  afterwards,  with  the  aid  of  Mr.  Con- 
rad, traced  one  of  them  to  a  Miocene  marl  pit  in  Cumberland  county,  New  Jersey. 
The  other  (the  Plesiosaurus  of  Harlan),  labelled  "  Mullica  Hill"  in  the  Museum, 
would  no  doubt  be  an  upper  cretaceous  fossil,  if  really  derived  from  that 
locality,  but  its  mineral  condition  makes  the  point  rather  doubtful.  The  tooth 
of  Stenorhynchus  veins,  figured  by  Leidy  from  a  drawing  of  Conrad's  (Proceed, 
of  Acad.  Nat.  Sci.  Philad.  1853,  p.  377),  was  found  by  Samuel  R.  Wetherhill, 
Esq.,  in  the  greensand  1£  miles  southeast  of  Burlington.  This  gentleman  re- 
lated to  me  and  Mr.  Conrad,  in  1853,  the  circumstances  under  which  he  met 
with  it,  associated  with  Ammonites  placenta,  Ammonites  Delawarensis,  Trigonia 
thoracica,  <fec.  The  tooth  has  been  mislaid,  but  not  until  it  had  excited  much 
interest  and  had  been  carefully  examined  by  good  zoologists. 

f  Proceedings  of  the  Gec4.  Soc.  vol.  iv.  p.  39  L 


256  LOWEK  GREENS  AND.  [Cn.  XVIII. 

life  at  this  period,  exerted  their  full  intensity  through  the  Indian,  Euro- 
pean, and  American  seas.*  Here,  as  in  North  and  South  America,  the 
cretaceous  character  can  be  recognized  even  where  there  is  no  specific 
identity  in  the  fossils ;  and  the  same  may  be  said  of  the  organic  type  of 
those  rocks  in  Europe  and  India  which  occur  next  to  the  chalk  in  the 
ascending  and  descending  order,  namely,  the  Eocene  and  the  Oolitic. 


CHAPTER  XVIII. 


LOWER  CRETACEOUS  AND  WEALDEN  FORMATIONS. 

Lower  Greensand — Term  "  N"eocomian"-rAtherfield  section,  Isle  of  Wight — 
Fossils  of  Lower  Greensand — Wealden  Formation — Freshwater  strata  interca- 
lated between  two  marine  groups — "Weald  Clay  and  Hastings  Sand — Fossil 
shells,  fish,  and  plants  of  Wealden — Their  relation  to  the  Cretaceous  type — 
Geographical  extent  of  "Wealden — Movements  in  the  earth's  crust  to  which  the 
Wealden  owed  its  origin  and  submergence — Flora  of  the  Lower  Cretaceous  and 
Wealden  Periods. 

THE  term  "  Lower  Greensand"  has  hitherto  been  most  commonly  ap- 
plied to  such  portions  of  the  Cretaceous  series  as  are  older  than  the  Gault. 
But  the  name  has  often  been  complained  of  as  inconvenient,  and  not  with- 
out reason,  since  green  particles  are  wanting  in  a  large  part  of  the  strata 
so  designated,  even  in  England,  and  wholly  so  in  some  European  coun- 
tries. Moreover,  a  subdivision  of  the  Upper  Cretaceous  group  has  like- 
wise been  called  Greensand,  and  to  prevent  confusion  the  terms  tipper 
and  Lower  Greensand  were  introduced.  Such  a  nomenclature  naturally 
leads  the  uninitiated  to  suppose  that  the  two  formations  so  named  are  of 
somewhat  co-ordinate  value,  which  is  so  far  from  being  true,  that  the 
Lower  Greensand,  in  its  widest  acceptation,  embraces  a  series  nearly  as 
important  as  the  whole  Upper  Cretaceous  group,  from  the  Gault  to  the 
Maestricht  beds  inclusive ;  while  the  Upper  Greensand  is  but  one  sub- 
ordinate member  of  this  same  group.  Many  eminent  geologists  have, 
therefore,  proposed  the  term  "Neocomian"  as  a  substitute  for  Lower 
Greensand  ;  because,  near  Neufchatel  (Neocomum),  in  Switzerland,  these 
Lower  Greensand  strata  are  well  developed,  entering  largely  into  the 
structure  of  the  Jura  -mountains.  By  the  same  geologists  the  Wealden 
beds  are  usually  classed  as  "  Lower  Neocomian,"  a  classification  which 
will  not  appear  inappropriate  when  we  have  explained,  in  the  sequel,  the 
intimate  relation  of  the  Lower  Greensand  and  Wealden  fossils. 

Dr.  Fitton,  to  whom  we  are  indebted  for  an  excellent  monograph  on 
the  Lower  Cretaceous  (or  Greensand)  formation  as  developed  in  England, 
gives  the  following  as  the  succession  of  rocks  seen  in  parts  of  Kent. 

*  See  Forbes,  Quart.  Geol.  Journ.  vol.  i.  p.  79. 


CH.  XVIIL]       ATHEKFIELD   SECTION,   ISLE   OF   WIGHT.  257 

No.  1.  Sand,  white,  yellowish,  or  ferruginous,  with  concretions 

of  limestone  and  chert  .  -  -  70  feet. 

2.  Sand  with  green  matter    .  -  -  70  to  100  feet. 

3.  Calcareous  stone,  called  Kentish  rag      -  -  60  to  80  feet. 

In  his  detailed  description  of  the  fine  section  displayed  at  Atherfield, 
in  the  south  of  the  Isle  of  Wight,  we  find  the  limestone  wholly  wanting ; 
in  fact,  the  variations  in  the  mineral  composition  of  this  group,  even  in 
contiguous  districts,  is  very  great ;  and  on  comparing  the  Atherfield  beds 
with  corresponding  strata  at  Hythe  in  Kent,  distant  95  miles,  the  whole 
series  presents  a  most  dissimilar  aspect.* 

On  the  other  hand,  Professor  E.  Forbes  has  shown  that  when  the 
sixty-three  strata  at  Atherfield  are  severally  examined,  the  total  thick- 
ness of  which  he  gives  as  843  feet,  there  are  some  fossils  which  range 
through  the  whole  series,  others  which  are  peculiar  to  particular  di- 
visions. As  a  proof  that  all  belong  chronologically  to  one  system, 
he  states  that  whenever  similar  conditions  are  repeated  in  overlying 
strata  the  same  -species  reappear.  Changes  of  depth,  or  of  the  mineral 
nature  of  the  sea-bottom,  the  presence  or  absence  of  lime  or  of  peroxide 
of  iron,  the  occurrence  of  a  muddy,  or  a  sandy,  or  a  gravelly  bottom, 
are  marked  by  the  banishment  of  certain  species  and  the  predominance 
of  others.  But  these  differences  of  conditions  being  mineral,  chemical, 
and  local  in  their  nature,  have  nothing  to  do  with  the  extinction, 
throughout  a  large  area,  of  certain  animals  or  plants.  The  rule  laid 
down  by  this  eminent  naturalist  for  enabling  us  to  test  the  arrival  of  a 
new  state  of  things  in  the  animate  world,  is  the  representation  by  new 
and  different  species  of  corresponding  genera  of  mollusca  or  other  beings. 
When  the  forms  proper  to  loose  sand  or  soft  clay,  or  a  stony  or  cal- 
careous bottom,  or  a  moderate  or  a  great  depth  of  water,  recur  with 
all  the  same  species,  the  interval  of  time  has  been,  geologically  speak- 
ing, small,  however  dense  the  mass  of  matter  accumulated.  But  if, 
the  genera  remaining  the  same,  the  species  are  changed,  we  have  en- 
tered upon  a  new  period;  and  no  similarity  of  climate,  or  of  geo- 
graphical and  local  conditions,  can  then  recall  the  old  species  which  a 
long  series  of  destructive  causes  in  the  animate  and  inanimate  world  has 
gradually  annihilated.  On  passing  from  the  Lower  Greensand  to  the 
Gault,  we  suddenly  reach  one  of  these  new  epochs,  scarcely  any  of  the 
fossil  species  being  common  to  the  lower  and  upper  cretaceous  sys- 
tems, a  break  in  the  chain  implying  no  doubt  many  missing  links  in 
the  series  of  geological  monuments,  which  we  may  some  day  be  able  to 
supply. 

One  of  the  largest  and  most  abundant  shells  in  the  lowest  strata  of  the 
Lower  Greensand,  as  displayed  in  the  Atherfield  section,  is  the  large 
Perna  Mulleti,  of  which  a  reduced  figure  is  here  given  (fig.  296). 

*  Dr.  Fitton,  Quart  Geol.  Journ.,  vol.  L  p.  179,  ii.  p.  55,  and  iii.  p.  289,  where 
comparative  sections  and  a  valuable  table  showing  the  vertical  range  of  the  va- 
rious fossils  of  the  lower  greensand  at  Atherfield  are  given. 

17 


258  FOSSILS   OF  LOWER   GREENSAND.  [On.  XVIII 

Fig.  296. 


Perna  Mulleti.    Desh.  in  Leym. 
a.  Exterior.  &.  Part  of  hinge  of  upper  valve. 


In  the  south  of  England,  during  the  accumulation  of  the  Lower  Green- 
sand  above  described,  the  bed  of  the  sea  appears  to  have  been  continually 
sinking,  from  the  commencement  of  the  period,  when  the  freshwater 
Wealden  beds  were  submerged,  to  the  deposition  of  those  strata  on  which 
the  gault  immediately  reposes. 

Pebbles  of  quartzose  sandstone,  jasper,  and  flinty  slate,  together  with 
grains  of  chlorite  and  mica,  speak  plainly  of  the  nature  of  the  pre-existing 
rocks,  from  the  wearing  down  of  which  the  Greensand  beds  were  derived. 
The  land,  consisting  of  such  rocks,  was  doubtless  submerged  before  the 
origin  of  the  white  chalk,  a  deposit  which  originated  in  a  more  open  sea, 
and  in  clearer  waters. 

The  fossils  of  the  Lower  Cretaceous  are  for  the  most  part  specifically 
distinct  from  those  of  the  Upper  Cretaceous  strata. 

Among  the  former  we  often  meet  with  the  genus  Scaphites  (fig.  297) 


Fig.  297. 


Fig.  293. 


Nautilus  plicatus,  Sow.. 
Fitton's  Monog. 


Scaphites  gigaa,  Sow.    Syn.  Ancyloceraa  gigas,  D'Orb. 


Cn.  XVIII.] 


WEALDEN"  FORMATION. 


259 


or  Ancyloceras,  which  has  been  aptly  described  as  an  ammonite  more  or 
less  uncoiled  ;  also  a  furrowed  Nautilus,  N.  plicatus  (fig.  298),  Trigonia 
caudata,  likewise  found  in  the  Blackdown  beds  (see  above,  p.  251),  and 
Gcrvillia,  a  bivalve  genus  allied  to  Avicula. 


Fig.  299. 


Fig.  300. 


Fig.  301. 


Trigonia  caudata,  Agass. 


GertiUia  anceps,  Desh. 


Terebratitlasdla,  Sow. 


WEALDEN    FORMATION. 

Beneath  the  Lower  Greensand  in  the  S.  E.  of  England,  a  freshwater 
formation  is  found,  called  the  Wealden  (see  Nos.  5  and  6,  Map,  fig.  320, 
p.  271),  which,  although  it  occupies  a  small  horizontal  area  in  Europe, 
as  compared  to  the  White  Chalk  and  Greensand,  is  nevertheless  of  great 
geological  interest,  since  the  imbedded  remains  give  us  some  insight  into 
the  nature  of  the  terrestrial  fauna  and  flora  of  the  Lower  Cretaceous  epoch. 
The  name  of  Wealden  was  given  to  this  group  because  it  was  first  studied 
in  parts  of  Kent,  Surrey,  and  Sussex,  called  the  Weald  (see  Map,  p.  271) ; 
and  we  are  indebted  to  Dr.  Mantell  for  having  shown,  in  1822,  in  his 
Geology  of  Sussex,  that  the  whole  group  was  of  fluviatile  origin.  In 
proof  of*  this  he  called  attention  to  the  entire  absence  of  Ammonites,  Be- 
lemnites,  TerebratulaB,  Echinites,  Corals,  and  other  marine  fossils,  so  char- 
acteristic of  the  cretaceous  rocks  above,  and  of  the  Oolitic  strata  below, 
and  to  the  presence  in  the  Weald  of  Paludinse,  Melanin,  and  various  flu- 
viatile shells,  as  well  as  the  bones  of  terrestrial  reptiles  and  the  trunks  and 
leaves  of  land  plants. 

The  evidence  of  so  unexpected  a  fact  as  the  infra-position  of  a  dense 
mass  of  purely  freshwater  origin  to  a  deep-sea  deposit  (a  phenomenon 
with  which  we  have  since  become  familiar)  was  received,  at  first,  with  no 
small  doubt  and  incredulity.  But  the  relative  position  of  the  beds  is  un- 
equivocal ;  the  Weald  Clay  being  distinctly  seen  to  pass  beneath  the  Lower 
Greensand  in  various  parts  of  Surrey,  Kent,  and  Sussex,  and  to  reappear 
in  the  Isle  of  Wight  at  the  base  of  the  Cretaceous  Series,  being,  no  doubt, 
continuous  far  beneath  the  surface,  as  indicated  by  the  dotted  lines  in  the 
annexed  diagram,  fig.  302. 


Isle  of  Wight 


«, -Chalk 


:>.  Greensand.        c.  Weald  Clay.        d.  Hastings  Sand.        e.  Purbeck  beds. 


260  WEALD   CLAY.  [Cte.  XVIIT 

The  Wealden  is  di\7isible  into  two  minor  groups : 

Thickness. 
1st.  "Weald  Clay,  chiefly  argillaceous,  but  sometimes  including 

thin  beds  of  sand  and  shelly  limestone  with  Paludina  140  to    280  ft. 
2d.  Hastings  Sand,  chiefly  arenaceous,  but  in  which  occur  some 

clays  and  calcareous  grits*         -  -  400  to  1000  ft. 

Another  freshwater  formation,  called  the  Purbeck,  consisting  of  various 
limestones  and  marls,  containing  distinct  species  of  mollusks,  Oypridet, 
and  other  fossils,  lies  immediately  beneath  the  Wealden  in  the  southeast 
of  England.  As  it  is  now  found  to  be  more  nearly  related,  by  its  organic 
remains,  to  the  Oolitic  than  to  the  Cretaceous  series,  it  will  be  treated  of 
in  the  20th  chapter. 

Weald  Clay. 

The  upper  division,  or  Weald  Clay,  is  of  purely  freshwater  origin.  Its 
highest  beds  are  not  only  conformable,  as  Dr.  Fitton  observes,  to  the 
inferior  strata  of  the  Lower  Greensand,  but  of  similar  mineral  composition. 
To  explain  this,  we  may  suppose,  that,  as  the  delta  of  a  great  river  was 
tranquilly  subsiding,  so  as  to  allow  the  sea  to  encroach  upon  the  space 
previously  occupied  by  fresh  water,  the  river  still  continued  to  carry  down 
the  same  sediment  into  the  sea.  In  confirmation  of  this  view  it  may  be 
stated,  that  the  remains  of  the  Iguanodon  Mantelli,  a  gigantic  terrestrial 
reptile,  very  characteristic  of  the  Wealden,  has  been  discovered  near 
Maidstone,  in  the  overlying  Kentish  rag,  or  Marine  limestone  of  the 
Lower  Greensand.  Hence  we  may  infer,  that  some  of  the  saurians  which 
inhabited  the  country  of  the  great  river  continued  to  live  when  part  of 
the  country  had  become  submerged  beneath  the  sea.  Thus,  in  our  OWE 
times,  we  may  suppose  the  bones  of  large  alligators  to  be  frequently  en- 
tombed in  recent  freshwater  strata  in  the  delta  of  the  Ganges.  But  if 
part  of  that  delta  should  sink  down  so  as  to  be  covered  by  the  sea,  marine 
formations  might  begin  to  accumulate  in  the  same  space  where  freshwater 
beds  had  previously  been  formed  ;  and  yet  the  Ganges  might  still  pour 
down  its  turbid  waters  in  the  same  direction,  and  carry  seaward  the  car- 
cases of  the  same  species  of  alligator,  in  which  case  their  bones  might  be 
included  in  marine  as  well  as  in  subjacent  freshwater  strata. 

The  Iguanodon,  first  discovered  by  Dr.  Mantell,  has  left  more  of  its 
remains  in  the  Wealden  strata  of  the  southeastern  counties  and  Isle  of 
Wight  than  has  any  other  genus  of  associated  saurians.  It  was  an  her- 
bivorous reptile,  and  regarded  by  Cuvier  as  more  extraordinary  than  any 
with  which  he  was  acquainted  ;  for  the  teeth,  though  bearing  a  great 
analogy,  in  their  general  form  and  crenated  edges  (see  figs.  303,  a, 
303,  6),  to  the  modern  Iguanas  which  now  frequent  the  tropical  woods 
of  America  and  the  West  Indies,  exhibit  many  striking  and  important 
differences.  It  appears  that  they  have  often  been  worn  by  the  process  of 
mastication ;  whereas  the  existing  herbivorous  reptiles  clip  and  gnaw  off 

*  Dr.  Fitton,  Geol.  Trans.  Second  Series,  vol.  iv.  p.  320. 


CH.  XVIII]  FOSSILS   OF  THE   WEALDEN   GROUP. 


261 


the  vegetable  productions  on  which  they  feed,  but  do  not  chew  them. 
Their  teeth  frequently  present  an  appearance  of  having  been  chipped  off, 
but  never,  like  the  fossil  teeth  of  the  Iguanodon,  have  a  flat  ground  sur- 
face (see  fig.  304,  6),  resembling  the  grinders  of  herbivorous  mammalia. 


Fig.  303. 


Fig.  804 


Fig.  303.  a,  &.  Tooth  of  Iguanodon  Mantetti. 
Fig  304.   «.  Partially  worn  tooth  of  young  individual  of  the  same, 
&.  Crown  of  tooth  in  adult,  worn  down.    (MantelL) 

Dr.  Mantell  computes  that  the  teeth  and  bones  of  this  species  which 
passed  under  his  examination  during  twenty  years  must  have  belonged  to 
no  less  than  seventy-one  distinct  individuals,  varying  in  age  and  magni- 
tude from  the  reptile  just  burst  from  the  egg,  to  one  of  which  the  femur 
measured  24  inches  in  circumference.  Yet,  notwithstanding  that  the 
teeth  were  more  numerous  than  any  other  bones,  it  is  remarkable  that  it 
was  not  until  the  relics  of  all  these  individuals  had  been  found,  that  a 
solitary  example  of  part  of  a  jaw-bone  was  obtained.  More  recently 
remains  both  of  the  upper  and  lower  jaw  have  been  met  with  in  the 
Hastings  Beds  in  Tilgate  Forest.  Their  size  was  somewhat  greater  than 
had  been  anticipated,  and  Dr.  Mantell,  who  does  not  agree  with  Professor 
Owen  that  the  tail  was  short,  estimates  the  probable  length  of  some  of 
these  saurians  at  between  50  and  60  feet.  The  largest  femur  yet  found 
measures  4  feet  8  inches  in  length,  the  circumference  of  the  shaft  being 
25  inches,  and,  if  measured  round  the  condyles,  42  inches. 

Occasionally  bands  of  limestone,  called  Sussex  Marble,  occur  in  the 
Weald  Clay,  almost  entirely  composed  of  a  species  of  Paludina,  closely 
resembling  the  common  P.  vivipara  of  English  rivers. 

Shells  of  the  Oypris,  a  genus  of  Crustaceans  before  mentioned  (p.  31) 
as  abounding  in  lakes  and  ponds,  are  also  plentifully  scattered  through  the 
clays  of  the  Wealden,  sometimes  producing,  like  plates  of  mica,  a  thin 
lamination  (see  fig.  307).  Similar  cypris-bearing  marls  are  found  in  the 
lacustrine  tertiary  beds  of  Auvergne  (see  above,  p.  199). 


262  FOSSILS  OF  THE  WEALDEN  GROUP.  [On.  XVIII. 

Fig.  306.  Fig.  806.  Fig.  807. 


Cypris 

spinigera, 

Fitton. 


Cypris  Valdensis,  Fitton. 
(C.faba,  Min.  Con.  4S5.) 


Weald  clay  with  Cypridcs. 


Hastings  Sands. 


This  lower  division  of  the  Wealden  consists  of  sand,  calciferous  grit, 
clay,  and  shale  ;  the  argillaceous  strata,  notwithstanding  the  name,  being 
nearly  in  the  same  proportion  as  the  arenaceous.  The  calcareous  sand- 
stone and  grit  of  Tilgate  Forest,  near  Cuckfield,  in  which  the  remains  01 
the  Iguanodon  and  Hylseosaurus  were  first  found,  constitute  an  upper 
member  of  this  formation.  The  white  "  sand-rock"  of  the  Hastings  cliffs, 
about  100  feet  thick,  is  one  of  the  lower  members  of  the  same.  The  rep- 
tiles, which  are  very  abundant  in  this  division,  consist  partly  of  saurians, 
already  referred  by  Owen  and  Mantell  to  eight  genera,  among  which, 
besides  those  already  enumerated,  we  find  the  Megalosaurus  and  Plesio- 
saurus.  The  Pterodactyl  also,  a  flying  reptile,  is  met  with  in  the  same 
strata,  and  many  remains  of  Chelonians  of  the  genera  Trionyx  and  Emys, 
now  confined  to  tropical  regions. 

The  fishes  of  the  Wealden  are  chiefly  referable  to  the  Ganoid  and 
Placoid  orders.  Among  them  the  teeth  and  scales  of  Lepidotus  are  most 
widely  diffused  (see  fig.  308).  These  ganoids  were  allied  to  the  Lepidos- 

Fig.  308. 


Lepidotus  ManteM,  Agass.    Wealden. 
Palate  and  teeth.  Z>.  Side  view  of  teeth. 


c.  Scale. 


tens,  or  Gar-pike,  of  the  American  rivers.  The  whole  body  was  covered 
with  large  rhomboidal  scales,  very  thick,  and  having  the  exposed  part 
coated  with  enamel.  Most  of  the  species  of  this  genus  are  supposed  to 
have  been  either  river-fish,  or  inhabitants  of  the  sea  at  the  mouth  of 
estuaries. 

The  shells  of  the  Hastings  beds  belong  to  the  genera  Melanopsis,  Me- 
lama,  Paludina,  Cyrena,  Cyclas,  Unio  (see  fig.  309),  and  others,  which 
inhabit  rivers  or  lakes ;  but  one  band  has  been  found  at  Punfield,  in  Dor- 
setshire, indicating  a  brackish  state  of  the  water,  where  the  genera  Corbula 
(see  fig.  310),  Mytilus,  and  Ostrea  occur;  and  in  some  places  this  bed 


CH.  XVIILJ  WEALDEK  FOSSILS. 

Fig.  309. 


263 


Fig.  310. 


Corbula,  alata,  Fitton.    Magnified. 

In  brackish-water  beds  of  the  Hastings 

Sands,  Pnnfield  Bay. 


TJnio  Valdervtix,  Mant 

Isle  of  Wight  and  Dorsetshire ;  in  the  lower  beds 
of  the  Hastings  Sands. 

becomes  purely  marine,  the  species  being  for  the  most  part  peculiar,  but 
several  of  them  well-known  Lower  Greensand  fossils,  among  which  Am- 
monites Deshayesii  may  be  mentioned.  These  facts  show  how  closely 
related  were  the  faunas  of  the  "Wealden  and  Cretaceous  periods. 

At  different  heights  in  the  Hastings  Sand,  we  find  again  and  again 
slabs  of  sandstone  with  a  strong  ripple-mark,  and  between  these  slabs  beds 
of  clay  many  yards  thick.  In  some  places,  as  at  Stammerham,  near 
Horsham,  there  are  indications  of  this  clay  having  been  exposed  so  as  to 
dry  and  crack  before  the  next  layer  was  thrown  down  upon  it.  The  open 
cracks  in  the  clay  have  served  as  moulds,  of  which  casts  have  been  taken 
in  relief,  and  which  are  therefore  seen  on  the  lower  surface  of  the  sand- 
stone (see  fig.  311). 

Fig.  811. 


Underside  of  slab  of  sandstone  about  one  yard  in  diameter. 
Stammerham,  Sussex. 

Near  the  same  place  a  reddish  sandstone  occurs  in  which  are  innu- 
merable traces  of  a  fossil  vegetable,  apparently  Sphenopteris,  the  stems 
and  branches  of  which  are  disposed  as  if  the  plants  were  standing 
erect  on  the  spot  where  they  originally  grew,  the  sand  having  been 
gently  deposited  upon  and  around  them ;  and  similar  appearances 


264 


AREA   OF  THE   WEALDEN. 


[CH.  XVIII 


Fig.  312. 


Sphenopteris  (/racilis  (Fitton),  from  the 

Hastings  Sands  near  Tunbridge  Wells. 

a.  A  portion  of  the  same  magnified. 


have  been  remarked  in  other  places  in  this  formation.*  In  the  sam« 
division  also  of  the  Wealden,  at  Cuck- 
iield,  is  a  bed  of  gravel  or  conglomer- 
ate, consisting  of  water-worn  pebbles  of 
quartz  and  jasper,  with  rolled  bones  of 
reptiles.  These  must  have  been  drifted 
by  a  current,  probably  in  water  of  no 
great  depth. 

From  such  facts  we  may  infer  that, 
notwithstanding  the  great  thickness  of 
this  division  of  the  Wealden,  the  whole 
of  it  was  a  deposit  in  water  of  a  moder- 
ate depth,  and  often  extremely  shallow. 
This  idea  may  seem  startling  at  first,  yet  such  would  be  the  natural  con- 
sequence of  a  gradual  and  continuous  sinking  of  the  ground  in  an  estuary 
or  bay,  into  which  a  great  river  discharged  its  turbid  waters.  By  each 
foot  of  subsidence,  the  fundamental  rock  would  be  depressed  one  foot 
farther  from  the  surface ;  but  the  bay  would  not  be  deepened,  if  newly 
deposited  mud  and  sand  should  raise  the  bottom  one  foot.  On  the  con- 
trary, such  new  strata  of  sand  and  mud  might  be  frequently  laid  dry  at 
low  water,  or  overgrown  for  a  season  by  a  vegetation  proper  to  marshes. 

Area  of  the  Wealden. — In  regard  to  the  geographical  extent  of  the 
Wealden,  it  cannot  be  accurately  laid  down ;  because  so  much  of  it  is 
concealed  beneath  the  newer  marine  formations.  It  has  been  traced 
about  200  English  miles  from  west  to  east,  from  the  coast  of  Dorsetshire 
to  near  Boulogne,  in  France  ;  and  nearly  200  miles  from  northwest  to 
southeast,  from  Surrey  and  Hampshire  to  Beauvais,  in  France.  If  the 
formation  be  continuous  throughout  this  space,  which  is  very  doubtful, 
it  does  not  follow  that  the  whole  was  contemporaneous;  because,  in 
all  likelihood,  the  physical  geography  of  the  region  underwent  frequent 
changes  throughout  the  whole  period,  and  the  estuary  may  have  altered 
its  form,  and  even  shifted  its  place.  Dr.  Dunker,  of  Cassel,  and  H. 
Von  Meyer,  in  an  excellent  monograph  on  the  Wealdens  of  Hanover 
and  Westphalia,  have  shown  that  they  correspond  so  closely,  not  only 
in  their  fossils,  but  also  in  their  mineral  characters,  with  the  English 
series,  that  we  can  scarcely  hesitate  to  refer  the  whole  to  one  great 
delta.  Even  then,  the  magnitude  of  the  deposit  may  not  exceed  that  of 
many  modern  rivers.  Thus,  the  delta  of  the  Quorra  or  Niger,  in  Africa, 
stretches  into  the  interior  for  more  than  170  miles,  and  occupies,  it  is 
supposed,  a  space  of  more  than  300  miles  along  the  coast,  thus  forming  a 
surface  of  more  than  25,000  square  miles,  or  equal  to  about  one  half  of 
England.f  Besides,  we  know  not,  in  such  cases,  how  far  the  fluviatile 
sediment  and  organic  remains  of  the  river  and  the  land  may  be  carried 
out  from  the  coast,  and  spread  over  the  bed  of  the  sea.  I  have  shown, 
when  treating  of  the  Mississippi,  that  a  more  ancient  delta,  including 

*  Mantell,  Geol.  of  S.  E.  of  England,  p.  244. 

f  Fitton,  Geol.  of  Hastings,  p.  58;  who  cites  Lander's  Travels. 


CH.  XVIIL]     LOWER  CRETACEOUS  AND   WEALDEN   FLORA.          265 

species  of  shells,  such  as  now  inhabit  Louisiana,  has  been  upraised,  and 
made  to  occupy  a  wide  geographical  area,  while  a  newer  delta  is  form- 
ing ;*  and  the  possibility  of  such  movements,  and  their  effects,  must  not 
be  lost  sight  of  when  we  speculate  on  the  origin  of  the  Wealden. 

If  it  be  asked  where  the  continent  was  placed  from  the  ruins  of  which 
the  Wealden  strata  were  derived,  and  by  the  drainage  of  which  a  great 
river  was  fed,  we  are  half  tempted  to  speculate  on  the  former  existence  of 
the  Atlantis  of  Plato.  The  story  of  the  submergence  of  an  ancient  conti- 
nent, however  fabulous  in  history,  must  have  been  true  again  and  again 
as  a  geological  event. 

The  real  difficulty  consists  in  the  persistence  of  a  large  hydrographical 
basin,  from  whence  a  great  body  of  fresh  water  was  poured  into  the  sea, 
precisely  at  a  period  when  the  neighboring  area  of  the  Wealden  was 
gradually  going  downwards  1000  feet  or  more  perpendicularly.  If  the 
adjoining  land  participated  in  the  movement,  how  could  it  escape  being 
submerged,  or  how  could  it  retain  its  size  and  altitude  so  as  to  continue 
to  be  the  source  of  such  an  inexhaustible  supply  of  freshwater  and  sedi- 
ment ?  In  answer  to  this  question,  we  are  fairly  entitled  to  suggest  that  the 
neighboring  land  may  have  been  stationary,  or  may  even  have  undergone 
a  contemporaneous  slow  upheaval.  There  may  have  been  an  ascending 
movement  in  one  region,  and  a  descending  one  in  a  contiguous  parallel 
zone  of  country ;  just  as  the  northern  part  of  Scandinavia  is  now  rising, 
while  the  middle  portion  (that  south  of  Stockholm)  is  unmoved,  and  the 
southern  extremity  in  Scania  is  sinking,  or  at  least  has  sunk  within  the 
historical  period.f  We  must,  nevertheless,  conclude,  if  we  adopt  the 
above  hypothesis,  that  the  depression  of  the  land  became  general  through- 
out a  large  part  of  Europe  at  the  close  of  the  Wealden  period,  and  this 
subsidence  brought  in  the  cretaceous  ocean. 

FLORA  OF  THE  LOWER  CRETACEOUS  AND  WEALDEN  PERIOD. 

The  terrestrial  plants  of  the  Upper  Cretaceous  epoch  are  but  little 
known,  as  might  be  expected,  since  the  rocks  are  of  purely  marine  origin, 
formed  for  the  most  part  far  from  land.  But  the  Lower  Cretaceous  or 
Neocomian  vegetation,  including  that  of  the  Weald  Clay  and  Hastings 
Sands,  is  by  no  means  scanty.  M.  Adolphe  Brongniart,  when  dividing 
the  whole  fossiliferous  series  into  three  groups  in  reference  solely  to  fossil 
plants,  has  named  the  primary  strata  "  the  age  of  acrogens  ;"  the  second- 
ary, exclusive  of  the  cretaceous,  "  the  age  of  gymnogens ;"  and  the  third, 
comprising  the  cretaceous  and  tertiary,  "  the  age  of  angiosperms."J  He 
considers  the  lower  cretaceous  flora  as  displaying  a  transitional  character 
from  that  of  a  secondary  to  that  of  a  tertiary  vegetation,  Coniferce  and 
Cycadea  (or  Gymnogens)  still  flourished,  as  in  the  preceding  oolitic  and 

*  See  above,  p.  84 ;  and  Second  Visit  to  the  U.  S.  vol.  ii.  chap,  xxxiv. 

f  See  the  Author's  Annivers.  Address,  GeoL  Soc.  1850,  Quart.  Geol.  Journ.  voL 
>  i.  p.  52. 

\  In  this  and  subsequent  remarks  on  fossil  plants  I  shall  often  use  Dr.  Lind-* 
ley's  terms,  as  most  familiar  in  this  country  ;  but  us  tlio-e  of  M.  A.  Brouyniart  are 


266         LOWER  CKETACEOUS  AND   WEALDEN   FLORA.      [Cn.  XVIIL 

triassic  epochs ;  but,  together  with  these,  some  well-marked  leaves  of 
dicotyledonous  trees,  of  a  genus  named  Credneria,  have  long  been  known. 
They  are  met  with  in  the  "  quader-sandstein"  and  "  pliiner-kalk"  of  Ger- 
many, rocks  of  the  Upper  Cretaceous  group.  More  recently,  Dr.  Deby 
has  discovered  in  the  Lower  Cretaceous  beds  of  Aix-la-Chapelle  a  great 
variety  of  dicotyledonous  leaves,*  belonging  to  no  less,  according  to  his 
enumeration,  than  26  species,  some  of  the  leaves  being  from  four  to  six 
inches  in  length,  and  in  a  beautiful  state  of  preservation.  In  the  absence 
of  the  organs  of  fructification  and  of  fossil  fruits,  the  number  of  species 
may  be  exaggerated ;  but  we  may  certainly  affirm,  reasoning  from  our 
present  data,  that  when  the  lower  chalk  of  Aix-la-Chapelle  originated. 
Dicotyledonous  Angiosperms  flourished  in  that  region  in  equal  proportions 
with  Gymnosperms.  This  discovery  has  an  important  bearing  on  some 
popular  theories,  for  until  lately  none  of  these  Exogeus  (a  class  now  con- 
stituting three-fourths  of  the  living  plants  of  the  globe)  had  been  detected 
in  any  strata  older  than  the  Eocene.  Moreover,  some  geologists  have 
wished  to  connect  the  rarity  of  dicotyledonous  trees  with  a  peculiarity  in 
the  state  of  the  atmosphere  in  the  earlier  ages  of  the  planet,  imagining 
that  a  denser  air  and  noxious  gases,  especially  carbonic  acid  gas  being  in 
excess,  were  adverse  to  the  prevalence,  not  only  of  the  quick-breathing 
classes  of  animals  (mammalia  and  birds),  but  to  a  flora  like  that  now  ex- 
isting, while  it  favored  the  predominance  of  reptile  life,  and  a  cryptogamic 
and  gymnospennous  flora.  The  coexistence,  therefore,  of  Dicotyledonous 
Angiosperms  in  abundance  with  Cycads  and  Coniferse,  and  with  a  rich 
reptilian  fauna,  comprising  the  Iguanodon,  Megalosaurus,  Hylaeosaurus, 
Ichthyosaurus,  Plesiosaurus,  and  Pterodactyl,  in  the  Lower  Cretaceous  se- 
ries, tends  manifestly  to  dispel  the  idea  of  a  meteorological  state  of  things 
in  the  secondary  periods  so  widely  distinct  from  that  now  prevailing. 

Among  the  recent  additions  made  to  the  fossil  flora  of  the  Wealden, 
and  one  which  supplies  a  new  link  between  it  and  the  tertiary  flora,  I 
may  mention  the  Gyrogonites,  or  spore-vessels  of  the  Cham,  lately  found 
in  the  Hastings  series  of  the  Isle  of  Wight. 

much  cited,  it  may  be  useful  to  geologists  to  give  a  table  explaining  the  corre- 
sponding names  of  groups  so  much  spoken  of  in  palaeontology. 

Brongniart.  Lindley. 

1.  Cryptogarnous     am-  } 

phigens,  or  cellular  >•       Thallogens.       Lichens,  sea- weeds,  fungi, 
cryptogamic.  J 

2.  Cryptogamous  aero-          Acrogens.          Mosses,  equisetums,  ferns,  lyco- 

gens.  podiums, — Lepidodendroa 

3.  Dicotyledonous  gym-          Gymnogens.      Conifers  and  Cycads. 

nosperms. 

4  Dicot.  Angiosperms.  Exogens.  Composites,  leguminosae,  umbel- 

liferse,  cruciferse,  heaths,  &c, 
All  native  European  trees  ex- 


cept conifers. 
6.  Monocotyledons.  Endogens.          Palms,  lilies, aloes, ruhes,  grasses, 

&c. 
*  Geol.  Quart.  Jour.  vol.  vii.  part  2,  Miscell.  p.  111. 


CH.XIX."!         INLAND  CHALK-CLIFFS  IN"  NORMANDY. 


CHAPTER  XLX. 

DENUDATION  OF  THE  CHALK  AND  WEALDEN. 

Physical  geography  of  certain  districts  composed  of  Cretaceous  and  Wealdeu 
strata — Lines  of  inland  chalk-cliffs  on  the  Seine  in  Normandy — Outstanding 
Dillars  and  needles  of  chalk — Denudation  of  the  chalk  and  Wealden  in  Surrey, 
Kent,  and  Sussex — Chalk  once  continuous  from  the  North  to  the  South  Downs 
— Anticlinal  axis  and  parallel  ridges — Longitudinal  and  transverse  valleys — 
Chalk  escarpments — Rise  and  denudation  of  the  strata  gradual — Ridges  formed 
by  harder,  valleys  by  softer  beds — At  what  periods  the  "Weald  valley  was  de- 
nuded— "Why  no  alluvium,  or  wreck  of  the  chalk,  in  the  central  district  of  the 
Weald — Land  has  most  prevailed  where  denudation  has  been  greatest — Ele- 
phant bed,  Brighton — Sangatte  Cliff — Conclusion. 

ALL  the  fossiliferous  formations  may  be  studied  by  the  geologist  in  two 
distinct  points  of  view ;  first,  in  reference  to  their  position  in  the  series, 
their  mineral  character  and  fossils;  and,  secondly,  in  regard  to  their 
physical  geography,  or  the  manner  in  which  they  now  enter,  as  mineral 
masses,  into  the  external  structure  of  the  earth ;  forming  the  bed  of  lakes 
and  seas,  or  the  surface  or  foundation  of  hills  and  valleys,  plains  and 
table-lands.  Some  account  has  already  been  given  on  the  first  head  of 
the  Tertiary,  the  Cretaceous,  and  the  Wealden  strata  ;  and  we  may  now 
proceed  to  consider  certain  features  in  the  physical  geography  of  these 
groups  as  they  occur  in  parts  of  England  and  France. 

The  hills  composed  of  white  chalk  in  the  S.  E.  of  England  have  a 
smooth  rounded  outline,  and  being  usually  in  the  state  of  sheep  pastures, 
are  free  from  trees  or  hedgerows ;  so  that  we  have  an  opportunity  of  ob- 
serving how  the  valleys  by  which  they  are  drained  ramify  in  all  directions, 
and  become  wider  and  deeper  as  they  descend.  Although  these  valleys 
are  now  for  the  most  part  dry,  except  during  heavy  rains  and  the  melting 
of  snow,  they  may  have  been  due  to  aqueous  denudation,  as  explained  in 
the  sixth  chapter ;  having  been  excavated  when  the  chalk  emerged  gradu- 
ally from  the  sea.  This  opinion  is  confirmed  by  the  occasional  occurrence 
of  what  appeared  to  be  long  lines  of  inland  cliffs,  in  which  the  strata  are 
cut  off  abruptly  in  steep  and  often  vertical  precipices.  The  true  nature  of 
such  escarpments  is  nowhere  more  obvious  than  in  parts  of  Normandy, 
\v  here  the  river  Seine  and  its  tributaries  flow  through  deep  winding  val- 
leys, hollowed  out  of  chalk  horizontally  stratified.  Thus,  for  example, 
if  we  follow  the  Seine  for  a  distance  of  about  30  miles  from  Andelys  to 
Elboeuf,  we  find  the  valley  flanked  on  both  sides  by  a  steep  slope  of 
chalk,  with  numerous  beds  of  flint,  the  formation  being  laid  open  for  a 
thickness  of  about  250  and  300  feet.  Above  the  chalk  is  an  overlying 
mass  of  sand,  gravel,  and  clay,  from  30  to  100  feet  thick.  The  two 
opposite  slopes  of  the  hills  a  and  b  (fig.  313),  where  the  chalk  appears  at 


268  INLAND   CHALK-CLIFFS  IN  NORMANDY.          [Cn.  XIX. 

Fig.  313. 


Section  across  Valley  of  Seine. 

the  surface,  are  from  2  to  4  miles  apart,  and  they  are  often  perfectly 
smooth  and  even,  like  the  steepest  of  our  downs  in  England ;  but  at 
many  points  they  are  broken  by  one,  two,  or  more  ranges  of  vertical 
and  even  overhanging  cliffs  of  bare  white  chalk  with  flints.  At  some 
points  detached  needles  and  pinnacles  stand  in  the  line  of  the  cliffs,  or 
in  front  of  them,  as  at  c,  fig.  313.  On  the  right  bank  of  the  Seine,  at 
Andelys,  one  range,  about  2  miles  long,  is  seen  varying  from  50  to  100 
feet  in  perpendicular  height,  and  having  its  continuity  broken  by  a  num- 
ber of  dry  valleys  or  coombs,  in  one  of  which  occurs  a  detached  rock  or 
needle,  called  the  Tete  d'Homme  (see  figs.  314,  315).  The  top  of  this 
rock  presents  a  precipitous  face  towards  every  point  of  the  compass ;  its 
vertical  height  being  more  than  20  feet  on  the  side  of  the  downs,  and  40 
towards  the  Seine,  the  average  diameter  of  the  pillar  being  36  feet.  Its 
composition  is  the  same  as  that  of  the  larger  cliffs  in  its  neighborhood, 
namely,  white  chalk,  having  occasionally  a  crystalline  texture  like  mar- 
ble, with  layers  of  flint  in  nodules  and  tabular  masses.  The  flinty  beds 
often  project  in  relief  4  or  5  feet  beyond  the  white  chalk,  which  is  gen- 
Fig.  314. 


View  of  the  Tete  d'Homme,  Andelys,  seen  from  above. 

erally  in  a  state  of  slow  decomposition,  either  exfoliating  or  being  cov- 
ered with  white  powder,  like  the  chalk  cliffs  on  the  English  coast ;  and, 
as  in  them,  this  superficial  powder  contains  in  some  cases  common  salt. 

Other  cliffs  are  situated  on  the  right  bank  of  the  Seine,  opposite 
Tournedos,  between  Andelys  and  Pont  de  1'Arche,  where  the  precipices 
are  from  50  to  80  feet  high :  several  of  their  summits  terminate  in  pin- 


Cn.  XIX.]  CLIFFS  OF   CHALK  IX   XORMANDY. 

Fig.  315. 


Side  view  of  the  Tete  d'Homme.    White  chalk  with  flints. 

nacles ;  and  one  of  them,  in  particular,  is  so  completely  detached  as  to 
present  a  perpendicular  face  50  feet  high  towards  the  sloping  down.  On 
these  cliffs  several  ledges  are  seen,  which  mark  so  many  levels  at  which 
the  waves  of  the  sea  may  be  supposed  to  have  encroached  for  a  long 
period.  At  a  still  greater  height,  immediately  above  the  top  of  this 
range,  are  three  much  smaller  cliffs,  each  about  4  feet  high,  with  as 
many  intervening  terraces,  which  are  continued  so  as  to  sweep  in  a  semi- 
circular form  round  an  adjoining  coomb,  like  those  in  Sicily  before  de- 
scribed (p.  76). 

If  we  then  descend  the  river  from  Vatteville  to  a  place  called  Senne- 
ville,  we  meet  with  a  singular  needle  about  50  feet  high,  perfectly  iso- 
lated on  the  escarpment  of  chalk  on  the  right  bank  of  the  Seine  (see  fig. 
248).  Another  conspicuous  range  of  inland  cliffs  is  situated  about  12 

Fig.  31&  Fig.  317. 


Chalk  pinnacle  at  Senneville. 


Eoches  d'Orival,  EltxeuC 


miles  below  on  the  left  bank  of  the  Seine,  beginning  at  Elbceuf,  and 
comprehending  the  Roches  d'Orival  (see  fig.  317).  Like  those  before 
described,  it  has  an  irregular  surface,  often  overhanging,  and  with  beds 


270 


CLIFFS  OF  CHALK  IN  NORMANDY. 


[On.  XIX. 


of  flint  projecting  several  feet.  Like  them,  also,  it  exhibits  a  white 
powdery  surface,  and  consists  entirely  of  horizontal  chalk  with  flints. 
It  is  40  miles  inland,  its  height,  in  some  parts,  exceeds  200  feet,  and 
its  base  is  only  a  few  feet  above  the  level  of  the  Seine.  It  is  broken,  in 
one  place,  by  a  pyramidal  mass  or  needle,  200  feet  high,  called  the 
Roche  de  Pignon,  which  stands  out  about  25  feet  in  front  of  the  upper 
portion  of  the  main  cliffs,  with  which  it  is  united  by  a  narrow  ridge 
about  40  feet  lower  than  its  summit  (see  fig.  318).  Like  the  detached 

Fig.  SiS. 


View  of  the  Koche  de  Pignon,  seen  from  the  south. 

rocks  before  mentioned  at  Senneville,  Vatteville,  and  Andelys,  it  may  be 
compared  to  those  needles  of  chalk  which  occur  on  the  coast  of  Nor- 
mandy* (see  fig.  319),  as  well  as  in  the  Isle  of  Wight  and  in  Purbeck. 

Fig.  319. 


Needle  and  Arch  of  Etretat,  in  the  chalk  cliffs  of  Normandy. 
Height  of  Arch  100  feet     (Passy.)t 

The  foregoing  description  and  drawings  will  show,  that  the  evidence 
of  certain  escarpments  of  the  chalk  having  been  originally  sea-cliffs,  is 
far  more  full  and  satisfactory  in  France  than  in  England.  If  it  be  asked 
why,  in  the  interior  of  our  own  country,  we  meet  with  no  ranges  of 
precipices  equally  vertical  and  overhanging,  and  no  isolated  pillars  or 
needles;  we  may  reply  that  the  greater  hardness  of  the  chalk  in  Nor- 
mandy may,  no  doubt,  be  the  chief  cause  of  this  difference.  But  the 

*  An  account  of  these  cliffs  was  read  by  the  author  to  the  British  Assoc.  at 
Glasgow,  Sept.  1840. 

f  Seine-Inferieure,  p.  14'2,  and  pi.  6,  fig.  1. 


CH.  XIX.]     DENUDATION  OF  THE   CHALK  AND  WEALDEJJT.        271 


frequent  absence  of  all  signs  of  littoral  denudation  in  the  valley  of  the 
Seine  itself  is  a  negative  fact  of  a  far  more  striking  and  perplexing  char- 
acter. The  cliffs,  after  being  almost  continuous  for  miles,  are  then  wholly 
wanting  for  much  greater  distances,  being  replaced  by  a  green  sloping 
down,  although  the  beds  remain  of  the  same  composition,  and  are  equally 
horizontal ;  and  although  we  may  feel  assured  that  the  manner  of  the 
upheaval  of  the  land,  whether  intermittent  or  not,  must  have  been  the 
same  at  those  intermediate  points  where  no  cliffs  exist,  as  at  others  where 
they  are  so  fully  developed.  But,  in  order  to  explain  such  apparent 
anomalies,  the  reader  must  refer  again  to  the  theory  of  denudation,  as 
expounded  in  the  6th  chapter ;  where  it  was  shown,  first,  that  the  under- 
mining force  of  the  waves  and  marine  currents  varies  greatly  at  different 
parts  of  every  coast ;  secondly,  that  precipitous  rocks  have  often  decom- 
posed and  crumbled  down ;  and  thirdly,  that  terraces  and  small  cliffs 
may  occasionally  lie  concealed  beneath  a  talus  of  detrital  matter. 

Denudation  of  the  Weald  Valley. — No  district  is  better  fitted  to  illus- 
trate the  manner  in  which  a  great  series  of  strata  may  have  been  up- 
heaved and  gradually  denuded  than  the  country  intervening  between  the 
North  and  South  Downs.  This  region,  of  which  a  ground-plan  is  given 
in  the  accompanying  map  (fig.  320),  comprises  within  it  the  whole  of 
Sussex,  and  parts  of  the  counties  of  Kent,  Surrey,  and  Hampshire.  The 
space  in  which  the  formations  older  than  the  White  Chalk,  or  those 
from  the  Gault  to  the  Hastings  sands  inclusive,  crop  out,  is  bounded 
everywhere  by  a  great  escarpment  of  chalk,  which  is  continued  on  the 
opposite  side  of  the  channel  in  the  Bas  Boulonnais  in  France,  where  it 
forms  the  semicircular  boundary  of  a  tract  in  which  older  strata  also  ap- 
pear at  the  surface.  The  whole  of  this  district  may  therefore  be  consid- 
ered geologically  as  one  and  the  same. 

Fig.  320. 


.Estuary  ofTIiames 


Geological  map  of  the  southeast  of  England  and  part  of  France,  exhibiting  the  denudation 
of  the  Weald. 


1.  H~""n  Tertiary. 

-•  ^ J  Chalk  and  upper  greensand. 

3.  MM»  Gault. 

4.  fc^H  Lower  Greensand. 


Weald  clay. 
Hastings  sands. 


272         DENUDATION   OF  THE   CHALK  AND  WEALDEN.    [On.  XIX. 

The  space  here  inclosed  within  the  escarpment  of  the  chalk  affords  an 
example  of  what  has  been  sometimes  called  a  "  valley  of  elevation" 
(more  properly  "  of  denudation") ;  where  the  strata,  partially  removed  by 
aqueous  excavation,  dip  away  on  all  sides  from  a  central  axis.  Thus,  it 


if 


S    J 

1 1 


t 


,  i 


a 


O     .j 
CO     <J> 

GO      o 


- 


;i 


CO 


S   cT 
11 


i 


CH.  XIX.]  TKAXSVERSE   VALLEYS.  .  273 

is  supposed,  that  the  area  now  occupied  by  the  Hastings  sand  (No.  6) 
was  once  covered  by  the  Weald  clay  (No.  5),  and  this  again  by  the 
Greensand  (No.  4),  and  this  by  the  Gault  (No.  3)  ;  and,  lastly,  tHt  the 
Chalk  (No.  2)  extended  originally  over  the  whole  space  between  the 
North  and  the  South  Downs.  This  theory  will  be  better  understood  by 
consulting  the  annexed  diagram  (fig.  321),  where  the  dark  lines  represent 
what  now  remains,  and  the  fainter  ones  those  portions  of  rock  which  are 
believed  to  have  been  carried  away. 

At  each  end  of  the  diagram  the  tertiary  strata  (No.  1)  are  exhibited 
reposing  on  the  chalk.  In  the  middle  are  seen  the  Hastings  sands  (No.  6.) 
forming  an  anticlinal  axis,  on  each  side  of  which  the  other  formations 
are  arranged  with  an  opposite  dip.  It  has  been  necessary,  however,  in 
order  to  give  a  clear  view  of  the  different  formations,  to  exaggerate  the 
proportional  height  of  each  in  comparison  to  its  horizontal  extent :  and  a 
true  scale  is  therefore  subjoined  in  another  diagram  (fig.  322),  in  order 
to  correct  the  erroneous  impression  which  might  otherwise  be  made  on 
the  reader's  mind.  In  this  section  the  distance  between  the  North  and 
South  Downs  is  represented  to  exceed  forty  miles ;  for  the  Valley  of  the 
Weald  is  here  intersected  in  its  longest  diameter,  in  the  direction  of  a 
line  between  Lewes  and  Maidstone. 

Through  the  central  portion,  then,  of  the  district  supposed  to  be  de- 
nuded runs  a  great  anticlinal  line,  having  a  direction  nearly  east  and 
west,  on  both  sides  of  which  the  beds  5,  4,  3,  and  2,  crop  out  in  succession. 
But,  although,  for  the  sake  of  rendering  the  physical  structure  of  this 
region  more  intelligible,  the  central  line  of  elevation  has  alone  been  in- 
troduced, as  in  the  diagrams  of  Smith,  Mantell,  Conybeare,  and  others, 
geologists  have  always  been  well  aware  that  numerous  minor  lines  of 
dislocation  and  flexure  run  parallel  to  the  great  central  axis. 

In  the  central  area  of  the  Hastings  sand  the  strata  have  undergone  the 
greatest  displacement ;  one  fault  being  known,  where  the  vertical  shift  of 
a  bed  of  calcareous  grit  is  no  less  than  60  fathoms.*  Much  of  the  pic- 
turesque scenery  of  this  district  arises  from  the  depth  of  the  narrow  valleys 
and  ridges  to  which  the  sharp  bends  and  fractures  of  the  strata  have 
given  rise ;  but  it  is  also  in  part  to  be  attributed  to  the  excavating  power 
exerted  by  water,  especially  on  the  interstratified  argillaceous  beds. 

Besides  the  series  of  longitudinal  valleys  and  ridges  in  the  Weald, 
there  are  valleys  which  run  in  a  transverse  direction,  passing  through  the 
chalk  to  the  basin  of  the  Thames  on  the  one  side,  and  to  the  English 
Channel  on  the  other.  In  this  manner  the  chain  of  the  North  Downs  is 
broken  by  the  rivers  Wey,  Mole,  Darent,  Medway,  and  Stour ;  the  South 
Downs  by  the  Arun,  Adur,  Ouse,  and  Cuckmere.f  If  these  transverse 
hollows  could  be  filled  up,  all  the  rivers,  observes  Dr.  Conybeare,  would 
be  forced  to  take  an  easterly  course,  and  to  empty  themselves  into  the 
sea  by  Rornney  Marsh  and  Pevensey  Levels.  J 

*  Fitton,  Geol.  of- Hasting?,  p.  55.         f  Conybeare,  Outlines  of  GeoL  p.  81. 

18 


274: 


CHALK  ESCARPMENTS. 


[On.  XIX. 


Mr.  Martin  has  suggested  that  the  great  cross  fractures  of  the  chalk, 
which  have  become  river  channels,  have  a  remarkable  correspondence 
on  each  .side  of  the  valley  of  the  Weald  ;  in  several  instances  the  gorges 
in  the  North  and  South  Downs  appearing  to  be  directly  opposed  to  each 
other.  Thus,  for  example,  the  defiles  of  the  Wey  in  the  North  Downs, 
and  of  the  Arun  in  the  South,  seemed  to  coincide  in  direction  ;  and  in 

like  manner,  the  Ouse  corre- 
sponds to  the  Darent,  and  the 
Cuckmere  to  the  Medway.* 

Although  these  coincidences 
may,  perhaps,  be  accidental,  it 
is  by  no  means  improbable,  as 
hinted  by  the  author  above 
mentioned,  that  great  amount 
of  elevation  towards  the  centre 
of  the  Weald  district  gave  rise 
to  transverse  fissures.  And  as 
the  longitudinal  valleys  were 
connected  with  that  linear  move- 
ment which  caused  the  anti- 
clinal lines  running  east  and 
west,  so  the  cross  fissures  migh 
have  been  occasioned  by  the 
intensity  of  the  upheaving  force 
towards  the  centre  of  the  line. 

But  before  treating  of  the 
manner  in  which  the  upheaving 
movement  may  have  acted,  7 
shall  endeavor  to  make  the 
reader  more  intimately  acquaint- 
ed with  the  leading  geographi- 
cal features  of  the  district,  so 
far  as  they  are  of  geological  in- 
terest. 

In  whatever  direction  we  travel 
from  the  tertiary  strata  of  the 
basins  of  London  and  Hamp- 
shire towards  the  valley  of  the 
Weald,  we  first  ascend  a  slope 
of  white  chalk,  with  flints,  and 
then  find  ourselves  on  the  sum- 
mit of  a  declivity  consisting,  for 
the  most  part,  of  different  mem- 
bers of  the  chalk  formation ; 
below  which  the  upper  green- 


*   Geol.  of  Western  Sussex,  p.  61. 


CH.  XIX.] 


TRANSVERSE   VALLEYS. 


275 


sand,  and  sometimes,  also,  the  gault,  crop  out.  This  steep  declivity, 
is  the  great  escarpment  of  the  chalk  before  mentioned,  which  overhangs 
a  valley  excavated  chiefly  out  of  the  argillaceous  or  marly  bed,  termed 
Gault  (Xo.  3).  The  escarpment  is  continuous  along  the  southern  ter- 
mination of  the  North  Downs,  and  may  be  traced  from  the  sea,  at 
Folkestone,  westward  to  Guildford  and  the  neighborhood  of  Petersfield, 
and  from  thence  to  the  termination  of  the  South  Downs  at  Beachy 
Head.  In  this  precipice  or  steep  slope  the  strata  are  cut  off  abruptly, 
and  it  is  evident  that  they  must  originally  have  extended  farther.  In 
the  wood-cut  (fig.  323,  p.  274),  part  of  the  escarpment  of  the  South 
Downs  is  faithfully  represented,  where  the  denudation  at  the  base  of 
the  declivity  has  been  somewhat  more  extensive  than  usual,  in  conse- 
quence of  the  upper  and  lower  greensand  being  formed  of  very  inco- 
herent materials,  the  former,  indeed,  being  extremely  thin  and  almost 
wanting. 

The  geologist  cannot  fail  to  recognize  in  this  view  the  exact  likeness 
of  a  sea-cliff ;  and  if  he  turns  and  looks  in  an  opposite  direction,  or 
eastward,  towards  Beachy  Head  (see  fig.  324),  he  will  see  the  same  line 


Fig.  324. 


Chalk  escarpment,  as  seen  from  the  hill  above  Steyning,  Snssex.    The  castle  and  village 
of  Bramber  in  the  foreground. 

of  heights  prolonged.  Even  those  who  are  not  accustomed  to  specu- 
late on  the  former  changes  which  the  surface  has  undergone  may  fancy 
the  broad  and  level  plain  to  resemble  the  flat  sands  which  were  laid  dry 
by  the  receding  tide,  and  the  different  projecting  masses  of  chalk  to  be 
the  headlands  of  a  coast  which  separated  the  different  bays  from  each 
other. 

Occasionally  in  the  North  Downs  sand-pipes  are  intersected  in  the 
slope  of  the  escarpment,  and  have  been  regarded  by  some  geologists 
as  more  modern  than  the  slope;  in  which  case  they  might  afford  an 
argument  against  the  theory  of  these  slopes  having  originated  as  sea- 
cliffs  or  river-cliffs.  But  when  we  observe  the  great  depth  of  many 
sand-pipes,  those  near  Sevenoaks,  for  example,  we  perceive  that  the 
lower  termination  of  such  pipes  must  sometimes  appear  at  the  sur- 
face far  from  the  summit  of  an  escarpment,  whenever  portions  of  the 
chalk  are  cut  away. 

In  regard  to  the  transverse  valleys  before  mentioned,  as  intersecting 
the  chalk  hills,  some  idea  of  them  may  be  derived  from  the  subjoined 


276 


TKANSVERSE  VALLEYS. 


XIX, 


[\ 

JV: 


i 


sketch  (fig.  325)  of  the  gorge  of  the  River  Adur,  taken  from  the  sum- 
mit of  the  chalk-downs,  at  a  point  in  the  bridle-way  leading  from  the 
towns  of  Bramber  and  Steyning  to  Shoreham.  If  the  reader  will  refer 
again  to  the  view  given  in  a  former  woodcut  (fig.  323,  p.  274),  he 
will  there  see  the  exact  point  where  the  gorge  of  which  I  am  now 
speaking  interrupts  the  chalk  escarpment.  A  projecting  hill,  at  the 
point  a,  hides  the  town  of  Steyning,  near  which  the  valley  commences 

where  the  Adur  passes  directly 
to  the  sea  at  Old  Shoreham.  The 
river  flows  through  a  nearly  level 
plain,  as  do  most  of  the  others 
which  intersect  the  hills  of  Surrey, 
Kent,  and  Sussex ;  and  it  is  evi- 
dent that  these  openings  could 
not  have  been  produced  by  rivers, 
except  under  conditions  of  physi- 
cal geography  entirely  different 
from  those  now  prevailing.  In- 
deed, many  of  the  existing  rivers, 
like  the  Ouse  near  Lewes,  have 
filled  up  arms  of  the  sea,  instead 
of  deepening  the  hollows  which 
they  traverse. 

That  the  place  of  some,  if  not 
of  all,  the  gorges  running  north 
and  south,  has  been  originally  de- 
termined by  the  fracture  and  dis- 
placement of  the  rocks,  seems  the 
more  probable,  when  we  reflect  on 
the  proofs  obtained  of  a  ravine 
running  east  and  west,  which 
branches  off  from  the  eastern  side 
of  the  valley  of  the  Ouse  just 
mentioned,  and  which  is  undoubt- 
edly due  to  dislocation.  This  ra- 
vine is  called  "  the  Coomb"  (fig. 
326),  and  is  situated  in  the  sub- 
urbs of  the  town  of  Lewes.  It 
was  first  traced  out  by  Dr.  Man- 
tell,  in  whose  company  I  exam- 
ined it.  The  steep  declivities  on 
each  side  are  covered  with  green 
turf,  as  is  the  bottom,  which  is 
perfectly  dry.  No  outward  signs 
of  disturbance  are  visible ;  and 
the  connection  of  the  hollow  with 
subterranean  movements  would 


C*.  XIX.] 


COOMB  NEAR  LEWES. 


277 


not  have  been  suspected  by  the  geologist,  had  not  the  evidence  of  great 
convulsions  been  clearly  exposed  in  the  escarpment  of  the  valley  of  the 

Fig;  826. 


The  Coomb,  near  Lewes. 

Ouse,  and  the  numerous  chalk-pits  worked  at  the  termination  of  the 
Coomb.  By  the  aid  of  these  we  discover  that  the  ravine  coincides  pre- 
cisely with  a  line  of  fault,  on  one  side  of  which  the  chalk  with  flints  (a, 
fig.  327)  appears  at  the  summit  of  the  hill,  while  it  is  thrown  down  to 
the  bottom  on  the  other. 

Fig.  327. 


Fault  coinciding  with  the  Coomb,  in  the  Cliff-hill  near  Lewes.    ManteU. 
a.  Chalk  with  flints.  5.  Lower  chalk. 


In  order  to  account  for  the  manner  in  which  the  five  groups  of  strata, 
2,  3,  4,  5,  6,  represented  in  the  map,  fig.  320,  and  in  the  section,  fig.  321, 
may  have  been  brought  into  their  present  position,  the  following  hypoth- 
esis has  been  suggested  : — Suppose  the  five  formations  to  lie  in  horizontal 
stratification  at  the  bottom  of  the  sea ;  then  let  a  movement  from  below 
press  them  upwards  into  the  form  of  a  flattened  dome,  and  let  the  crown 
of  this  dome  be  afterwards  cut  off,  so  that  the  incision  should  penetrate  to 
the  lowest  of  the  five  groups.  The  different  beds  would  then  be  exposed 
on  the  surface,  in  the  manner  exhibited  in  the  map,  fig.  320.* 

*  See  illustrations  of  this  theory,  by  Dr.  Fitton,  Geol.  Sketch  of  Hastings. 


278  PROMINENCE    OF   HARDER   STRATA.  [Cn.  XIX. 

The  quantity  of  denudation,  or  removal  by  water,  of  stratified  masses 
assumed  to  have  once  reached  continuously  from  the  North  to  the  South 
Downs  is  so  enormous,  that  the  reader  may  at  first  be  startled  by  the 
boldness  of  the  hypothesis.  But  the  difficulty  will  disappear  when  once 
sufficient  time  is  allowed  for  the  gradual  rising  and  sinking  of  the 
strata  at  many  successive  geological  periods,  during  which  the  waves 
and  currents  of  the  ocean,  and  the  power  of  rain,  rivers,  and  land-floods, 
might  slowly  accomplish  operations  which  no  sudden  diluvial  rush  of 
waters  could  possibly  effect. 

Among  other  proofs  of  the  action  of  water,  it  may  be  stated  that  the 
great  longitudinal  valleys  follow  the  outcrop  of  the  softer  and  more 
incoherent  beds,  while  ridges  or  lines  of  cliff  usually  occur  at  those 
points  where  the  strata  are  composed  of  harder  stone.  Thus,  for  ex- 
ample, the  chalk  with  flints,  together  with  the  subjacent  upper  green- 
sand,  which  is  often  used  for  building,  under  the  provincial  name 
of  "  firestone,"  have  been  cut  into  a  steep  cliff  on  that  side  on  which 
the  sea  encroached.  This  escarpment  bounds  a  deep  valley,  exca- 
vated chiefly  out  of  the  soft  argillaceous  bed,  termed  gault  (No.  3. 
map,  p.  272).  In  some  places  the  upper  greensand  is  in  a  loose 
and  incoherent  state,  and  there  it  has  been  as  much  denuded  as 
the  gault ;  as,  for  example,  near  Beachy  Head ;  but  farther  to  the 
westward  it  is  of  great  thickness,  and  contains  hard  beds  of  blue 
chert  and  calcareous  sandstone  or  firestone.  Here,  accordingly,  we 
find  that  it  produces  a  corresponding  influence  on  the  scenery  of  the 
country;  for  it  runs  out  like  a  step  beyond  the  foot  of  the  chalk 
hills,  and  constitutes  a  lower  terrace,  varying  in  breadth  from  a  quar 
ter  of  a  mile  to  three  miles,  and  following  the  sinuosities  of  the .  chalk 
escarpment.* 

Fig.  828. 


a.  Chalk  with  flints.  5.  Chalk  without  flints. 

c.  Upper  greensand,  or  firestone.  d.  Gault. 

It  is  impossible  to  desire  a  more  satisfactory  proof  that  the  escarp- 
ment is  due  to  the  excavating  power  of  water  during  the  rise  of  the 
strata,  or  during  their  rising  and  sinking  at  successive  periods ;  for 
I  have  shown,  in  my  account  of  the  coast  of  Sicily  (p.  76),  in  what 
manner  the  encroachments  of  the  sea  tend  to  efface  that  succession 
of  terraces  which  must  otherwise  result  from  the  intermittent  up- 
heaval of  a  coast  preyed  upon  by  the  waves.  During  the  inter- 

*  Sir  R.  Murchison,  Geol.  Sketch  of  Sussex,  <fec ,  Geol.  Trans.,  Second  Series, 
vol.  ii.  p.  93. 


CH.  XIX.]  DENUDATION   OF  THE   WEALD.  279 

val  between  two  elevatory  movements,  the  lower  terrace  will  usually 
be  destroyed,  wherever  it  is  composed  of  incoherent  materials 
whereas  the  sea  will  not  have  time  entirely  to  sweep  away  another 
part  of  the  same  terrace,  or  -lower  platform,  which  happens  to  be 
composed  of  rocks  of  a  harder  texture,  and  capable  of  offering  a 
firmer  resistance  to  the  erosive  action  of  water.  As  the  yielding 
clay  termed  gault  would  be  readily  washed  away,  we  find  its  out- 
crop marked  everywhere  by  a  valley  which  skirts  the  base  of  the 
chalk-hills,  and  which  is  usually  bounded  on  the  opposite  side  by 
the  lower  areensand :  but  as  the  upper  beds  of  this  last  formation 

O  JT  A 

are  most  commonly  loose  and  incoherent,  they  also  have  usually 
disappeared  and  increased  the  breadth  of  the  valley.  In  those  dis- 
tricts, however,  where  chert,  limestone,  and  other  solid  materials  en- 
ter largely  into  the  composition  of  this  formation  (No.  4,  map,  p. 
272),  they  give  rise  to  a  range  of  hills  parallel  to  the  chalk,  which 
sometimes  rival  the  escarpment  of  the  chalk  itself  in  height,  or 
even  surpass  it,,  as  in  Leith  Hill,  near  Dorking.  This  ridge  often 
presents  a  steep  escarpment  towards  the  soft  argillaceous  deposit 
called  the  Weald  clay  (No.  5 ;  see  the  dark  tint  in  figure  321. 
p.  272),  which  usually  forms  a  broad  valley,  separating  the  lower 
greensand  from  the  Hastings  sands  or  Forest  Ridge ;  but  where  sub- 
ordinate beds  of  sandstone  of  a  firmer  texture  occur,  the  uniformity 
of  the  plain  of  No.  5  is  broken  by  waving  irregularities  and  hil- 
locks. 

Pluvial  action.  —  In  considering,  however,  the  comparative  de- 
structibility  of  the  harder  and  softer  rocks,  we  must  not  underrate 
the  power  of  rain.  The  chalk-downs,  even  on  their  summits,  are 
usually  covered  with  unrounded  chalk-flints,  such  as  might  remain 
after  masses  of  white  chalk  had  been  softened  and  removed  by  water. 
This  superficial  accumulation  of  the  hard  or  siliceous  materials  of 
disintegrated  strata  may  be  due  in  no  small  degree  to  pluvial  action 
for  during  extraordinary  rains  a  rush  of  water  charged  with  calca- 
reous matter,  of  a  milk-white  color,  may  be  seen  to  descend  even 
gently  sloping  hills  of  chalk.  If  a  layer  no  thicker  than  the  tenth 
of  an  inch  be  removed  once  in  a  century,  a  considerable  mass  may 
in  the  course  of  indefinite  ages  melt  away,  leaving  nothing  save  a 
stratum  of  flinty  nodules  to  attest  its  former  existence.  A  bed  of  fine 
clay  sometimes  covers  the  surface  of  slight  depressions  in  the  white 
chalk,  which  may  represent  the  aluminous  residue  of  the  rock,  after 
the  pure  carbonate  of  lime  has  been  dissolved  by  rain-water,  charged 
with  excess  of  carbonic  acid  derived  from  decayed  vegetable  matter. 
The  acidulous  waters  sometimes  descend  through  "  sand-pipes"  and 
"  swallow-holes"  in  the  chalk,  so  that  the  surface  may  be  undermined, 
and  cavities  may  be  formed  or  enlarged,  even  by  that  part  of  the  drain- 
age which  is  subterranean.* 

*  See  above,  p.  82,  83,  "  Sand-pipes  in  Chalk  ;"  and  Prestwich,  Geol.  Quart, 
Journ.  voL  x.  p.  222. 


280  THEORY   OE   FRACTURE   AND  UPHEAVAL.        [Ca  XIX. 

Lines  of  Fracture. — Mr.  Martin,  in  his  work  on  the  g'eology  of  West- 
ern Sussex,  published  in  1828,  threw  much  light  on  the  structure  of 
the  Wealden  by  tracing  out  continuously  for  miles  the  direction  of 
many  anticlinal  lines  and  cross  fractures ;  and  the  same  course  of  investi- 
gation has  since  been  followed  out  in  greater  detail  by  Mr.  Hopkins. 
The  geologist  and  mathematician  last  mentioned  has  shown  that  the 
observed  direction  of  the  lines  of  flexure  and  dislocation  in  the  Weald 
district  coincide  with  those  which  might  have  been  anticipated  theo- 
retically on  mechanical  principles,  if  we  assume  certain  simple  conditions 
under  which  the  strata  were  lifted  up  by  an  expansive  subterranean 
force.* 

His  opinion,  that  both  the  longitudinal  and  transverse  lines  of  frac- 
ture may  have  been  produced  simultaneously,  accords  well  with  that 
expressed  by  M.  Thurmann,  in  his  work  on  the  anticlinal  ridges  and 
valleys  of  elevation  of  the  Bernese  Jura.f  For  the  accuracy  of  the  map 
and  sections  of  the  Swiss  geologist  I  can  vouch,  from  personal  exami- 
nation, in  1835,  of  part  of  the  region  surveyed  by  him.  Among  other 
results,  at  which  he  arrived,  it  appears  that  the  breadth  of  the  anticli- 
nal ridges  and  dome-shaped  masses  in  the  Jura  is  invariably  great  ir. 
proportion  to  the  number  of  the  formations  exposed  to  view;  or,  in 
other  words,  to  the  depth  to  which  the  superimposed  groups  of  sec- 
ondary strata  have  been  laid  open.  (See  fig.  71,  p.  55,  for  structure 
of  Jura.)  He  also  remarks,  that  the  anticlinal  lines  are  occasionally 
oblique  and  cross  each  other,  in  which  case  the  greatest  dislocation 
of  the  beds  takes  place.  Some  of  the  cross  fractures  are  imagined  by 
him  to  have  been  contemporaneous  with  others  subsequent  to  the  lon- 
gitudinal ones. 

I  have  assumed,  in  the  former  part  of  this  chapter,  that  the  rise  of 
the  Weald  was  gradual,  whereas  many  geologists  have  attributed  its 
elevation  to  a  single  effort  of  subterranean  violence.  There  appears 
to  them  such  a  unity  of  effect  in  this  and  other  lines  of  deranged 
strata  in  the  southeast  of  England,  such  as  that  of  the  Isle  of  Wight, 
as  is  inconsistent  with  the  supposition  of  a  great  number  of  separate 
movements  recurring  after  long  intervals  of  time.  But  we  know  that 
earthquakes  are  repeated  throughout  a  long  series  of  ages  in  the 
same  spots,  like  volcanic  eruptions.  The  oldest  lavas  of  JStna  were 
poured  out  many  thousands,  perhaps  myriads  of  years  before  the 
newest,  and  yet  they,  and  the  movements  accompanying  their  emis- 
sion, have  produced  a  symmetrical  mountain ;  and  if  rivers  of  melted 
matter  thus  continue  to  flow  upwards  in  the  same  direction,  and 
towards  the  same  point,  for  an  indefinite  lapse  of  ages,  what  diffi- 
culty is  there  in  conceiving  that  the  subterranean  volcanic  force, 
occasioning  the  rise  or  fall  of  certain  parts  of  the  earth's  crust, 
may,  by  reiterated  movements,  produce  the  most  perfect  unity  of 
result  ? 

*  Geol  Soc.  Proceed.  No.  74,  p.  363,  1841,  and  G.  S.  Trans.  2  Ser.  vol.  7. 
f  Soul^vemens  Jurassiques.     1832. 


CH.  XIX.]     PERIODS   OF   DENUDATION   IN  THE   WEALD.  281 

At  what  periods  the  Weald  valley  was  denuded. —  We  may  next 
inquire  at  what  time  the  denudation  of  the  Weald  was  effected,  and 
we  shall  find,  on  considering  all  the  facts  brought  to  light  by  recent 
investigation,  that  it  was  accomplished  in  the  course  of  so  long  a 
series  of  ages,  that  the  greatest  revolutions  in  the  physical  geography 
of  the  globe,  yet  known  to  us,  have  taken  place  within  the  same 
lapse  of  time.  It  has  now  been  ascertained,  that  part  of  the  denu- 
dation of  the  Weald  was  completed  before  the  British  Eocene  strata, 
and  consequently  before  the  numinulitic  rocks  of  Europe  and  Asia  were 
formed.  The  date,  therefore,  of  part  of  the  changes  now  under  contem- 
plation was  long  antecedent  to  the  existence  of  the  Alps,  Pyrenees,  and 
many  other  European  and  Asiatic  mountain-chains,  and  even  to  the 
accumulation  of  large  portions  of  their  component  materials  beneath 
the  sea. 

M.  Elie  de  Beaumont  suggested,  in  1833,  that  there  was  an  island 
in  the  Eocene  sea  in  the  area  now  occupied  by  the  French  and 
English  Wealden  strata,  and  he  gave  a  map  or  hypothetical  restora- 
tion of  the  ancient  geography  of  that  region  at  the  era  alluded  to.* 
Mr.  Prestwich  has  since  shown  that  the  materials  of  which  the  lower 
tertiary  beds  of  England  are  made  up,  and  their  manner  of  resting 
on  the  chalk,  imply,  that  such  an  island,  or  several  islands  and  shoals, 
composed  of  Chalk,  Upper  Greensand,  Gault,  and  probably  of  some 
of  the  Lower  Cretaceous  rocks,  did  exist  somewhere  between  the  present 
North  and  South  Downs.  The  undermined  cliffs  and  shores  of  those 
lands  supplied  the  flints,  which  the  action  of  the  waves  rounded  into 
pebbles,  such  as  now  form  the  Woolwich  and  Blackheath  shingle- 
beds  below  the  London  Clay.  It  is  supposed,  that  the  land  referred 
to  was  drained  by  rivers  flowing  into  the  Eocene  sea,  and  whence 
the  brackish  and  freshwater  deposits  of  Woolwich  and  other  contem- 
poraneous strataf  were  derived.  The  large  size  of  some  of  the  rolled 
flints  (eight  inches  and  upwards  in  diameter)  of  the  Blackheath  shingle 
demonstrates  the  proximity  of  land.  Such  heavy  masses  could  not 
have  been  transported  from  great  distances,  whether  they  owe  their 
shape  to  waves  breaking  on  a  sea-beach,  or  to  rivers  descending  a  steep 
slope. 

In  the  annexed  diagram  (fig.  329)  Mr.  Prestwich  has  represented 
a  section  from  near  Saffron  Walden,  in  Essex,  to  the  Weald,  passing 
north  and  south  through  Godstone,  in  which  we  see  how  the  chalk, 
c,  had  been  disturbed  and  denuded  before  the  lower  Eocene  beds,  6, 
were  deposited.  Some  small  patches  of  the  last-mentioned  beds,  &', 
consisting  of  clay  and  sand,  extend  occasionally,  as  in  this  instance, 
to  the  very  edge  of  the  escarpment  of  the  North  Downs,  proving  that 
the  surface  of  the  white  chalk,  now  covered  with  tertiary  strata,  is 
the  same  which  originally  constituted  the  bottom  of  the  Eocene  sea. 

*  Mem.  de  la  Soc.  Ge"ol.  de  France,  vol.  i.  part  i.  p.  Ill,  pL  7,  fig.  5. 
f  See  p.  220,  above. 


282  ISLANDS   IN  THE   EOCENE    SEA.  [On.  XIX 

Fig.  329. 

G 


Section  showing  that  the  "Weald  had  been  denuded  of  chalk  before  the  Lower  Eocene  strata  were 

deposited 

S.  Relative  position  of  Saffron  Walden. 

G.  Chalk-escarpment  above  Godstone,  surmounted  by  a  patch  of  the  Lower  Tertiary  beds,  &'. 
a.  London  Clay.  &,  6'.  Lower  Tertiaries.  c.  Chalk. 

d.  Upper  Greensand.          e.  Gault.  /  Lower  Greensand  and  Wealden. 

x.  Point  at  which  the  present  upper  and  under  surfaces  of  the  chalk,  if  they  were  prolonged 
would  converge. 

It  is  therefore  inferred,  that,  if  we  prolong  southwards  the  upper  and 
under  surfaces  of  the  chalk,  along  the  dotted  line  in  the  above  section, 
they  would  converge  at  the  point  x ;  therefore,  beyond  that  point,  no 
white  chalk  existed  at  the  time  when  the  Eocene  beds,  5,  &',  were  formed. 
In  other  words,  the  central  parts  of  the  Wealden,  south  of  x,  were  already 
bared  of  their  original  covering  of  chalk,  or  had  only  some  slight  patches 
of  that  rock  scattered  over  them. 

The  island,  or  islands,  in  the  Eocene  sea  may  be  represented  in  the 
annexed  diagram  (fig.  330) ;  but  doubtless  the  denudation  extended 

Fig.  830. 


Island  in  the  Eocene  Sea. 
a.  Chalk,  Upper  Greensand,  and  Gault.  Z>.  Lower  Greensand. 


c.  "Wealden. 


farther  in  width  and  depth  before  the  close  of  the  Eocene  period,  and  the 
waves  may  have  cut  into  the  Lower  Greensand,  and  perhaps  in  some 
places  into  the  Wealden  strata. 

According  to  this  view  the  mass  of  cretaceous  and  subcretaceous  rocks, 
planed  off  by  the  waves  and  currents  in  the  area  between  the  North  and 
South  Downs  before  the  origin  of  the  oldest  Eocene  beds,  may  have  been 
as  voluminous  as  the  mass  removed  by  denudation  since  the  commence- 
ment of  the  Eocene  era. 

But  the  reader  may  ask,  why  is  it  necessary  to  assume  that  so  much 
white  chalk  first  extended  continuously  over  the  "Wealden  beds  in  this 
part  of  England,  and  was  then  removed  ?  May  we  not  suppose  that  land 
began  to  exist  between  the  North  and  South  Downs  at  a  much  earlier 
epoch  ;  and  that  the  upper  Wealden  beds  rose  in  the  midst  of  the  Creta- 
ceous Ocean,  so  as  to  check  the  accumulation  of  white  chalk,  and  limit  it 
to  the  deeper  water  of  adjoining  areas  ?  This  hypothesis  has  often  been 
advanced,  and  as  often  rejected  ;  for,  had  there  been  shoals  or  dry  land 


CH.  XIX.]  WEALD,  WHEN  DENUDED.  283 

so  near,  the  white  chalk  would  not  have  remained  unsoiled,  or  without 
intermixture  of  mud  and  sand ;  nor  would  organic  remains  of  terrestrial, 
fluviatile,  or  littoral  origin  have  been  so  entirely  wanting  in  the  strata  of 
the  North  and  South  Downs,  where  the  chalk  terminates  abruptly  in  the 
escarpments.  It  is  admitted  that  the  fossils  now  found  there  belong  ex- 
clusively to  classes  which  inhabit  a  deep  sea.  Moreover,  the  uppermost 
beds  of  the  Wealden  group,  as  Mr.  Prestwich  has  remarked,  would  not 
have  been  so  strictly  conformable  with  the  lowest  beds  of  the  Lower 
Greensand  had  the  strata  of  the  Wealden  undergone  upheaval  before  the 
deposition  of  the  incumbent  cretaceous  series. 

But,  although  we  must  assume  that  the  white  chalk  was  once  contin- 
uous, over  what  is  now  the  Weald,  it  by  no  means  follows  that  the  first 
denudation  was  subsequent  to  the  entire  Cretaceous  era.  Most  probably 
it  commenced  before  a  large  portion  of  the  Maestricht  beds  were  formed, 
or  while  they  were  in  progress.  I  have  already  stated  (p.  238,  above), 
that  in  parts  of  Belgium  I  observed  rolled  pebbles  of  chalk-flints  very 
abundant  in  the  lowest  Maestricht  beds,  where  these  last  overlie  the  white 
chalk,  showing  at  how  early  a  date  the  chalk  was  upraised  from  deep 
water  and  exposed  to  aqueous  abrasion. 

Guided  by  the  amount  of  change  in  organic  life,  we  may  estimate  the 
interval  between  the  Maestricht  beds  and  the  Thanet  Sands  to  have  been 
nearly  equal  in  duration  to  the  time  which  elapsed  between  the  depo- 
sition of  those  same  Thanet  Sands  and  the  Glacial  period.  If  so,  it 
would  be  idle  to  expect  to  be  able  to  make  ideal  restorations  of  the  innu- 
merable phases  in  physical  geography  through  which  the  southeast  of 
England  must  have  passed  since  the  Weald  began  to  be  denuded.  In 
less  than  half  the  same  lapse  of  time  the  aspect  of  the  whole  European 
area  has  been  more  than  once  entirely  changed.  Nevertheless,  it  may  be 
useful  to  enumerate  some  of  the  known  fluctuations  in  the  physical  con- 
formation of  the  Weald  and  the  regions  immediately  adjacent  during  the 
period  alluded  to. 

First,  we  have  to  carry  back  our  thoughts  to  those  very  remote  move- 
ments which  first  brought  up  the  white  chalk  from  a  deep  sea  into 
exposed  situations  where  the  waves  could  plane  off  certain  portions,  as 
expressed  in  diagram  (fig.  329),  before  the  British  Lower  Eocene  beds 
originated. 

Secondly,  we  have  to  take  into  account  the  gradual  wear  and  tear  of 
the  chalk  and  its  flints,  to  which  the  Thanet  sands  bear  witness,  as  well  as 
the  subsequent  Woolwich  and  Blackheath  shingle -beds,  occasionally  50 
feet  thick,  and  composed  of  rolled  flint-pebbles. 

Thirdly,  at  a  later  period  a  great  subsidence  took  place,  by  which  the 
shallow- water  and  freshwater  beds  of  Woolwich  and  other  Lower  Eocene 
deposits  were  depressed  (see  above,  p.  221)  so  as  to  allow  the  London 
Clay  and  Bagshot  series,  of  deep-sea  origin,  to  accumulate  over  them. 
The  amount  of  this  subsidence,  according  to  Mr.  Prestwich,  exceeded  800 
feet  in  the  London,  and  1800  feet  in  the  Hampshire  or  Isle  of  Wight 
basin  ;  and  if  so,  the  intervening  area  of  the  Weald  could  scarcely  fail  to 


284  AT  WHAT  PERIODS  [On.  XIX. 

share  in  the  movement,  and  some  parts  at  least  of  the  island  before 
spoken  of  (fig.  330,  p.  282)  would  become  submerged. 

Fourthly.  After  the  London  clay  and  the  overlying  Bagshot  sands  had 
been  deposited,  they  appear  to  have  been  upraised  in  the  London  basin, 
during  the  Eocene  period,  and  their  conversion  into  land  in  the  north 
seems  to  have  preceded  the  upheaval  of  beds  of  corresponding  age  in  the 
south,  or  in  the  Hampshire  basin ;  because  none  of  the  fluvio-marine 
Eocene  strata  of  Hordwell  and  th«  Isle  of  Wight  (described  in  CH.  XVI.) 
are  found  in  any  part  of  the  London  area. 

Fifthly.  The  fossils  of  the  alternating  marine,  brackish,  and  freshwater 
beds  of  Hampshire,  of  Middle  and  Upper  Eocene  date,  bear  testimony  to 
rivers  draining  adjacent  lands,  and  to  the  existence  of  numerous  quadru- 
peds in  those  lands.  Instead  of  these  phenomena,  the  signs  of  an  open 
sea  might  naturally  have  been  expected,  as  a  consequence  of  the  vast 
subsidence  of  the  Middle  Eocene  beds  before  mentioned,  had  not  some 
local  upheaval  taken  place  at  the  same  time  in  the  Isle  of  Wight  or  in 
regions  immediately  adjacent.  Whatever  hypothesis  be  adopted,  we  are 
entitled  to  assume  that  during  the  Middle  and  Upper  Eocene  periods 
there  were  risings  and  sinkings  of  land,  and  changes  of  level  in  the  bed  of 
the  sea  in  the  southeast  of  England,  and  that  the  movements  were  by  no 
means  uniform  over  the  whole  area  during  these  periods.  The  extent  and 
thickness  of  the  missing  beds  in  the  Weald  should  of  itself  lead  us  to  look 
for  proofs  of  that  area  having  by  repeated  oscillations  changed  its  level 
frequently,  and,  oftener  than  any  adjoining  area,  been  turned  from  sea  into 
land  ;  for  the  submergence  and  emergence  of  land  augment,  beyond  any 
other  cause,  the  wasting  and  removing  power  of  water,  whether  of  the 
waves  or  of  rivers  and  land-floods. 

Sixthly.  As  yet  we  have  discovered  no  Marine  Miocene  (or  falunian) 
formations  in  any  part  of  the  British  Isles,  nor  any  of  older  Pliocene 
date  south  of  the  Thames ;  but  the  Upper  Eocene  strata  of  the  Isle 
of  Wight  (the  Hempstead  beds  before  described)  have  been  upraised 
above  the  level  of  the  sea  in  which  they  were  originally  formed,  and 
some  of  them  have  been  thrown  into  a  vertical  position,  as  seen  in 
Alum  and  Whitecliff  Bays,  attesting  great  movements  since  the  origin 
of  the  newest  tertiaries  of  that  district.  Such  movements  may  have 
occurred,  in  great  part  at  least,  during  the  Miocene  period,  when  a 
large  part  of  Europe  is  supposed  to  have  become  land  as  before  sug- 
gested (p.  180).  Hence  we  are  entitled  to  speculate  on  the  probability 
of  revolutions  in  the  physical  geography  of  the  Weald  in  times  inter- 
mediate between  the  deposition  of  the  Hempstead  beds  and  the  origin  of 
the  Suffolk  crag. 

Seventhly.  But  we  have  still  to  consider  another  vast  interval  of  time 
— that  which  separated  the  beginning  of  the  older  Pliocene  from  the  be- 
ginning of  the  Pleistocene  era, — a  lapse  of  ages  which,  if  measured  by  the 
fluctuations  experienced  in  the  marine  fauna,  may  have  sufficed  to  uplift 
or  sink  whole  continents  by  a  process  as  slow  as  that  which  is  now  opera 
ting  in  Sweden  and  in  Greenland. 


CH.  XIX.]          THE  WEALD  VALLEY  WAS  DENUDED.  285 

Lastly.  The  reader  must  recall  to  mind  what  was  said  in  the  llth  and 
12th  chapters,  of  the  glacial  drift  and  its  far-transported  materials.  How 
wide  an  extent  of  the  British  Isles  appears  to  have  been  under  the  sea 
during  some  part  or  other  of  that  epoch !  Most  of  the  submerged  areas 
were  afterwards  converted  into  dry  land,  several  hundred  and  in  some 
places  more  than  a  thousand  feet  high.  It  is  an  opinion  very  com- 
monly entertained,  that  the  central  axis  of  the  Weald  was  dry  land  when 
the  most  characteristic  northern  drift  originated ;  no  traces  of  northern 
erratics  having  been  met  with  farther  south  than  Highgate,  near  London. 
If  such  were  the  case,  the  Weald  was  probably  dry  land  at  the  era  when 
the  buried  forest  of  Cromer  in  Norfolk  (see  above,  pp.  136  and  153) 
flourished,  and  when  the  elephant,  rhinoceros,  hippopotamus,  extinct 
beaver,  and  other  mammals  peopled  that  country.  It  may  also  be  pre- 
sumed that  the  Weald  continued  above  the  sea-level  when  that  forest 
sank  down  to  receive  its  covering  of  boulder-clay,  gravel,  chalk-rubble, 
and  other  deposits,  several  hundred  feet  thick.  But  it  by  no  means 
follows  that  the  area  of  the  Weald  was  stationary  during  all  this  period. 
Its  surface  may  have  been  modified  again  and  again  during  the  Glacial 
era,  though  it  may  never  have  been  submerged  beneath  the  sea. 

Mr.  Trimmer  has  represented  in  a  series  of  four  maps  his  views  as 
to  the  successive  changes  which  the  physical  geography  of  England  and 
parts  of  Europe  may  have  undergone,  after  the  commencement  of  the 
Glacial  epoch.*  In  the  last  but  one  of  these  he  places  the  Weald  under 
water  at  a  date  long  posterior  to  the  forest  of  Cromer.  In  the  fourth 
map  he  represents  the  Weald  as  reconverted  into  land  at  a  time  when 
England  was  united  to  the  continent,  and  when  the  Thames  was  a 
river  of  greater  volume  and  of  more  easterly  extension  than  it  is  now, 
as  proved  by  his  own  and  Mr.  Austen's  observations  on  the  ancient 
alluvium  of  the  Thames  with  its  freshwater  fossils  at  points  very  near 
the  sea.  To  discuss  the  various  data  on  which  such  conclusions  de- 
pend, would  lead  me  into  too  long  a  digression ;  I  merely  allude  to 
them  in  this  place  to  show  that,  while  the  researches  of  Mr.  Prest- 
wich  establish  the  extreme  remoteness  of  the  period  when  the  de- 
nuding operations  began,  those  of  other  geologists  above  cited,  to 
whom  Mr.  Martin,  Professor  Morris,  and  Sir  R.  Murchison  should  be 
added,  prove  that  important  superficial  changes  have  occurred  at  very 
modern  eras. 

In  Denmark,  especially  in  the  Island  of  Moen,  -Mr.  Puggaard  has  de- 
monstrated that  strata  of  chalk  with  flints,  nearly  as  thick  as  the  white 
chalk  of  the  Isle  of  Wight  and  Purbeck,  have  undergone  disturbances 
and  contortions  since  the  northern  drift  was  formed.f  The  layers  of 
chalk-flint  exposed  in  lofty  sea-cliffs  are  often  vertical  and  curved,  and 
the  sands  and  clays  of  the  overlying  drift  follow  the  bendings  and  foldings 
of  the  older  beds,  and  have  evidently  suffered  the  same  derangement. 
If,  therefore,  we  find  it  necessary,  in  order  to  explain  the  position 

*  Geol.  Quart.  Journ.  voL  ix.  pi.  13. 

•J-  Puggaard,  Moens  Geologic,  8vo. :  Copenhagen,  1851. 


286  WEALD,  HOW  DENUDED.  [Cn.  XIX. 

of  some  beds  of  gravel,  loam,  or  drift  in  the  southeast  of  Bug-land,  to  im- 
agine important  dislocations  of  the  chalk  and  local  changes  of  leyel  since 
the  Glacial  period,  such  speculations  are  in  harmony  with  conclusions 
derived  from  independent  sources,  or  drawn  from  the  exploration  of  for- 
eign countries. 

It  was  long  ago  observed  by  Dr.  Mantell  that  no  vestige  of  the  chalk 
and  its  flints  has  been  seen  on  the  central  ridge  of  the  Weald  or  on  the 
Hastings  Sands,  but  merely  gravel  and  loam  derived  from  the  rocks  im- 
mediately subjacent.  This  distribution  of  alluvium,  and  especially  the 
absence  of  chalk  detritus  in  the  central  district,  agrees  well  with  the 
theory  of  denudation  before  set  forth  ;  for,  to  return  to  fig.  321  (p.  273), 
if  the  chalk  (No.  2)  were  once  continuous  and  covered  everywhere  with 
flint-gravel,  this  superficial  covering  would  be  the  first  to  be  carried  away 
from  the  highest  part  of  the  dome  long  before  any  of  the  gault  (No.  3) 
was  laid  bare.  Now,  if  some  ruins  of  the  chalk  remain  at  first  on  the 
gault,  these  would  be,  in  a  great  degree,  cleared  away  before  any  part  of 
the  lower  greensand  (No.  4)  is  denuded.  Thus  in  proportion  to  the 
number  and  thickness  of  the  groups  removed  in  succession,  is  the  prob- 
ability lessened  of  our  finding  any  remnants  of  the  highest  group  strewed 
over  the  bared  surface  of  the  lowest. 

But  it  is  objected,  that,  had  the  sea  at  one  or  several  periods  been  the 
agent  of  denudation,  we  should  have  found  ancient  sea-beaches  at  the 
foot  of  the  escarpments,  and  other  signs  of  oceanic  erosion.  As  a  gen- 
eral rule,  the  wreck  of  the  white  chalk  and  its  flints  can  only  be  traced 
to  slight  distances  from  the  escarpments  of  the  North  and  South  Downs. 
Some  exceptions  occur,  one  of  which  was  first  pointed  out  to  me  in  1830, 
by  the  late  Dr.  Mantell.  In  this  case  the  flints  are  seen  near  Barcombe, 
three  miles  from  the  nearest  chalk,  as  indicated  in  the  annexed  section 
(fig.  331).  Even  here  it  will  be  seen  that  the  gravel  reaches  no  farther 

Fig.  331. 

Barcoinle 


Section  from  the  north  escarpment  of  the  South  Downs  to  Barcombe. 

A.  Layer  of  unrounded  chalk-flints. 

1.  Gravel  composed  of  partially  rounded  chalk-flints. 

2.  Chalk  Avith  and  without  flints. 

3.  Lowest  chalk  or  chalk-marl  (upper  greensand  wanting). 

4.  Gau'.t  5.  Lower  greensand.  6.  Weald  clay. 

than  the  Weald  clay.  But  it  is  worthy  of  remark,  that  such  depressions 
as  that  between  Barcombe  and  Offham  in  this  section,  arising  from  the 
facility  with  which  the  argillaceous  gault  (No.  4,  map  p.  272)  has  been 
removed  by  water,  are  usually  free  from  superficial  detritus,  although  such 
valleys,  situated  at  the  foot  of  escarpments,  where  there  has  been  much 
waste,  might  have  been  supposed  to  be  the  natural  receptacles  of  the 
wreck  of  the  undermined  cliffs.  The  question  is  therefore  often  put,  how 


CH.  XIX.] 


ELEPHANT-  BED . 


287 


these  hollows  could  have  been  swept  clean  except  by  some  extraordinary 
catastrophe. 

The  frequent  angularity  of  the  flints  in  the  drift  of  Barcombe  and 
other  places  is  also  insisted  upon  as  another  indication  of  denuding 
causes  differing  in  kind  and  degree  from  any  which  man  has  witnessed. 
But  all  who  have  examined  the  gravel  at  the  base  of  a  chalk-cliff,  in 
places  where  it  is  not  peculiarly  exposed  to  the  continuous  and  violent 
action  of  the  waves,  are  aware  that  the  flints  retain  much  angularity. 
This  may  be  seen  between  the  Old  Harry  rocks  in  Dorsetshire  and 
Christchurch  in  Hampshire.  Throughout  the  greater  part  of  that  line 
of  coast  the  cliffs  are  formed  of  tertiary  strata,  capped  by  a  dense 
covering  of  gravel  formed  of  flints  slightly  abraded.  As  the  waste  of 
the  cliffs  is  rapid,  the  old  materials  are  gradually  changed  for  new 
ones  on  the  beach ;  nevertheless  we  have  here  an  example  of  angles 
being  retained  after  two  periods  of  attrition ;  first,  where  the  gravel 
was  spread  originally  over  the  Eocene  deposits ;  and,  secondly,  after 
the  Eocene  sands  and  clays  were  undermined  and  the  modern  cliff 
formed. 

Angular  flint-breccia  is  not  confined  to  the  Weald,  nor  to  the  trans- 
verse gorges  in  the  chalk,  but  extends  along  the  neighboring  coast  from 
Brighton  to  Rottingdean,  where  it  was  called  by  Dr.  Mantell  "the 
elephant-bed,"  because  the  bones  of  the  mammoth  abound  in  it,  with 
those  of  the  horse  and  other  mammalia.  The  following  is  a  section  of 
this  formation  as  it  appears  in  the  Brighton  cliff.* 


Fig.  832. 


A.  Chalk  -with  layers  of  flint  dipping  slightly  to  the  south. 

&.  Ancient  beach,  consisting  of  fine  sand,  from  one  to  four  feet  thick,  covered  by  shingle  from 

five  to  eight  feet  thick  of  pebbles  of  chalk-flint,  granite,  and  other  rocks,  with  broken 

shells  of  recent  marine  species,  and  bones  of  cetacea. 
c.  Elephant-bed,  about  fifty  feet  thick,  consisting  of  layers  of  white  chalk  rubble,  with  broken 

chalk-flints,  often  more  confusedly  stratified  than  is  represented  in  this  drawing,  in  which 

deposit  are  found  bones  of  ox,  deer,  horse,  and  mammoth. 
&  Sand  and  shingle  of  modern  beach. 

*  See  also  Sir  R.  Murchison,  GeoL  Quart.  Journ.  voL  vii.  p.  365. 


288  SANGATTE  CLIFF.  [Cn.  XIX. 

To  explain  this  section  we  must  suppose  that,  after  the  excavation  of 
the  cliff  A,  the  beach  of  sand  and  shingle  b  was  formed  by  the  long- 
continued  action  of  the  sea.  The  presence  of  Littorina  littorea  and 
other  recent  littoral  shells  determines  the  modern  date  of  the  accumu- 
lation. The  overlying  beds  are  composed  of  such  calcareous  rubble  and 
flints,  rudely  stratified,  as  are  often  conspicuous  in  parts  of  the  Norfolk 
coast,  where  they  are  associated  with  glacial  drift,  and  were  probably  of 
contemporaneous  origin.  Similar  flints  and  chalk-rubble  have  been  re- 
cently traced  by  Sir  Roderick  Murchison  to  Folkestone  and  along  the 
face  of  the  cliffs  at  Dover,  where  the  teeth  of  the  fossil  elephant  have 
been  detected. 

Mr.  Prestwich  also  has  shown  that  at  Sangatte,  near  Calais,  on  the 
coast  exactly  opposite  Dover,  a  similar  waterworn  t«ach,  with  an  incum- 
bent mass  of  angular  flint-breccia,  is  visible.  I  have  myself  visited  this 
spot  and  found  the  deposit  strictly  analogous  to  that  of  Brighton.  The 
fundamental  ancient  beach  has  been  uplifted  more  than  10  feet  above  its 
original  level.  The  flint-pebbles  in  it  have  evidently  been  rounded  at  the 
base  of  an  ancient  chalk-cliff,  the  course  of  which  can  still  be  traced  in- 
land, nearly  parallel  with  the  present  shore,  but  with  a  space  intervening 
between  them  of  about  one-third  of  a  mile  in  its  greatest  breadth.  This 
space  is  occupied  by  a  terrace,  100  feet  in  its  greatest  height,  the  com- 
ponent materials  of  which  are  too  varied  and  complex  to  be  described 
here.  They  are  such  as  might,  I  conceive,  have  been  heaped  up  above 
the  sea-level  in  the  delta  of  a  river  draining  a  region  of  white  chalk.  The 
delta  may  perhaps  have  been  slowly  subsiding  while  the  strata  accumu- 
lated. Some  of  the  beds  of  chalk-rubble  with  broken  flints  appear  to 
have  had  channels  cut  in  them  before  the  uppermost  deposit  of  sand  and 
loam  was  thrown  down.  The  angularity  of  the  flints,  as  Mr.  Prestwich 
has  suggested,  may  be  owing  to  their  having  been  previously  shattered 
when  in  the  body  of  the  chalk  itself ;  for  we  often  see  flints  so  fractured 
in  situ  in  the  chalk,  especially  when  the  latter  has  been  much  disturbed. 
The  presence  also  in  this  Sangatte  drift  of  large  fragments  of  angular 
white  chalk,  some  of  them  two  feet  in  diameter,  should  be  mentioned. 
They  are  confusedly  mixed  with  smaller  gravel  and  fine  mud,  for  the 
most  part  devoid  of  stratification,  and  yet  often  too  far  from  the  old  cliffs 
to  have  been  a  talus.  I  therefore  suspect  that  the  waters  of  the  river 
and  its  tributaries  were  occasionally  frozen  over,  and  that  during  floods 
the  carrying  power  of  ice  co-operated  with  that  of  water  to  transport 
fragile  rocks  and  angular  flints,  leaving  them  unsorted  when  the  ice 
melted,  or  not  arranged  according  to  size  and  weight  as  in  deposits 
stratified  by  moving  water.  A  climate  like  that  now  prevailing  on  the 
borders  of  the  Baltic  or  in  Canada  might  produce  such  effects  long 
after  the  intense  cold  of  the  glacial  epoch  had  passed  away.  The  abun- 
dance of  mammalia  in  countries  where  rivers  are  liable  to  be  annually 
encumbered  with  ice,  is  a  fact  with  which  we  are  familiar  in  the  northern 
hemisphere,  and  the  frequency  of  fossil  remains  of  quadrupeds  in  forma- 
tions* of  glacial  origin  ought  not  to  excite  surprise.  As  to  the  angulariJty 


CIL  XIX.]  DENUDATION   OF  THE   WEALD.  289 

of  the  flints,  it  has  been  thought  by  some  authorities  to  imply  great  vio- 
lence in  the  removing  power,  especially  in  those  cases  where  well-rounded 
pebbles  washed  out  of  Eocene  strata  are  likewise  found  broken,  sometimes 
with  sharp  edges  and  often  with  irregular  pieces  chipped  out  of  them  as 
if  by  a  smart  blow.  Such  fractured  pebbles  occur  not  unfrequently  in 
the  drift  of  the  valley  of  the  Thames.  In  explanation,  I  may  remark  that, 
in  the  Blackheath  and  other  Eocene  shingle-beds,  hard  egg-shaped  flint- 
pebbles  may  be  found  in  such  a  state  of  decomposition  as  to  break  in  the 
same  manner  on  the  application  of  a  moderate  blow,  such  as  stones  might 
encounter  in  the  bed  of  a  swollen  river. 

To  conclude :  It  is  a  fact,  not  questioned  by  any  geologist,  that  the 
area  of  the  Weald  once  rose  from  beneath  the  sea  after  the  origin  of 
the  chalk,  that  rock  being  a  marine  product,  and  now  constituting  dry 
land.  Few  will  question,  that  part  of  the  same  area  remained  under 
water  until  after  the  origin  of  the  Eocene  deposits,  because  they  also 
are  marine,  and  reach  to  the  edge  of  the  chalk-downs.  Whether,  there- 
fore, we  do  or  do  not  admit  the  occurrence  of  reiterated  submersions 
and  emersions  of  land,  the  first  of  them  as  old  as  the  Upper  Cretaceous, 
the  last  perhaps  of  Newer  Pliocene  or  even  later  date,  we  are  at  least 
compelled  to  grant  that  there  was  a  time  when,  in  the  region  un'der 
consideration,  the  waters  of  the  sea  retreated.  The  presence  of  land 
and  river-shells,  and  the  bones  of  terrestrial  quadrupeds  in  some  of  the 
gravel,  loam,  and  flint-breccia  of  the  Weald,  may  indicate  a  fluviatile 
origin,  but  they  can  never  disprove  the  prior  occupation  of  the  area  by 
the  sea.  Heavy  rains,  the  slow  decomposition  of  rocks  in  the  atmo- 
sphere, land-floods,  and  rivers  (some  of  them  larger  than  those  now 
flowing  in  the  same  valleys)  may  have  modified  the  surface  and  ob- 
literated all  signs  of  the  antecedent  presence  of  the  sea.  Littoral  shells, 
once  strewed  over  ancient  shores,  or  buried  in  the  sands  of  the  beach, 
may  have  decomposed  so  as  to  make  it  impossible  for  us  to  assign  an 
exact  paleontological  date  to  the  older  acts  of  denudation ;  but  the  re- 
moval of  Chalk  and  Greensand  from  the  central  axis  of  the  Weald,  the 
leading  inequalities  of  hill  and  dale,  the  long  lines  of  escarpment,  the 
longitudinal  and  transverse  valleys,  may  still  be  mainly  due  to  the 
power  of  the  waves  and  currents  of  the  sea,  co-operating  with  that  up- 
heaval and  subsidence  and  dislocation  of  rocks  which  all  admit  to  have 
taken  place. 

In  despair  of  solving  the  problem  of  the  present  geographical  config- 
uration and  geological  structure  of  the  Weald  by  an  appeal  to  ordinary 
causation,  some  geologists  are  fain  to  invoke  the  aid  of  imaginary 
"rushes  of  salt  water"  over  the  land,  during  the  sudden  upthrow  of 
the  bed  of  the  sea,  when  the  anticlinal  axis  of  the  Weald  was  formed. 
Others  refer  to  vast  bodies  of  fresh  water  breaking  forth  from  subter- 
ranean reservoirs,  when  the  rocks  were  riven  by  earthquake-shocks  of  in- 
tense violence.  The  singleness  of  the  cause  and  the  unity  of  the  result 
are  emphatically  insisted  upon  :  the  catastrophe  was  abrupt,  tumultuous, 
transient,  and  paroxysmal ;  fragments  of  stone  were  swept  along  to  great 

19 


290  CONCLUSION.  [Cn.  XIX 

distances  without  time  being  allowed  for  attrition  ;  alluvium  was  thrown 
down  unstratified,  and  often  in  strange  situations,  on  the  flanks  or  on  the 
summits  of  hills,  while  the  lowest  levels  were  left  bare.  The  convulsion 
was  felt  simultaneously  over  so  wide  an  area  that  all  the  individuals  of 
certain  species  of  quadrupeds  were  at  once  annihilated ;  yet  the  event  was 
comparatively  modern,  for  the  species  of  testacea  now  living  were  already 
in  existence. 

This  hypothesis  is  surely  untenable  and  unnecessary.  In  the  present 
chapter  I  have  endeavored  to  show  how  numerous  have  been  the  periods 
of  geographical  change,  and  how  vast  their  duration.  Evidence  to  this 
effect  is  afforded  by  the  relative  position  of  the  chalk  and  overlying  ter- 
tiary deposits ;  by  the  nature,  character,  and  position  of  the  tertiary 
strata ;  and  by  the  overlying  alluvia  of  the  Weald  and  adjacent  countries. 
As  to  the  superficial  detritus,  its  insignificance  in  volume,  when  compared 
to  the  missing  rocks,  should  never  be  lost  sight  of.  A  mountain-mass  of 
solid  matter,  hundreds  of  square  miles  in  extent,  and  hundreds  of  yards  in 
thickness,  has  been  carried  away  bodily.  To  what  distance  it  has  been 
transported  we  know  not,  but  certainly  beyond  the  limits  of  the  Weald. 
For  achieving  such  a  task,  if  we  are  to  judge  by  analogy,  all  transient  and 
sudden  agency  is  hopelessly  inadequate.  There  is  one  power  alone  which 
is  competent  to  the  task,  namely,  the  mechanical  force  of  water  in  motion, 
operating  gradually,  and  for  ages.  We  have  seen  in  the  6th  chapter 
that  every  stratified  portion  of  the  earth's  crust  is  a  monument  of  denuda- 
tion on  a  grand  scale,  always  effected  slowly ;  for  each  superimposed 
stratum,  however  thin,  has  been  successively  and  separately  elaborated. 
Every  attempt,  therefore,  to  circumscribe  the  time  in  which  any  great 
amount  of  denudation,  ancient  or  modern,  has  been  accomplished,  draws 
with  it  the  gratuitous  rejection  of  the  only  kind  of  machinery  known  to 
us  which  possesses  the  adequate  power.  j;:^;:  :. 

If,  then,  at  every  epoch,  from  the  Cambrian  to  the  Pliocene  inclusive, 
voluminous  masses  of  matter,  such  as  are  missing  in  the  Weald,  have 
been  transferred  from  place  to  place,  and  always  removed  gradually,  it 
seems  extravagant  to  imagine  an  exception  in  the  very  region  where  we 
can  prove  the  first  and  last  acts  of  denudation  to  have  been  separated  by 
so  vast  an  interval  of  time.  Here,  might  we  say,  if  anywhere  within  the 
range  of  geological  inquiry,  we  have  time  enough  and  without  stint  at 
our  command. 


OH.  XX.]  DIVISIONS  OF  THE  OOLITE.  291 


CHAPTER   XX. 

JURASSIC  GROUP. PURBECK  BEDS  AND  OOLITE. 

The  Purbeck  beds  a  member  of  the  Jurassic  group— Subdivisions  of  that  group — 
Physical  geography  of  the  Oolite  in  England  and  France — Upper  Oolite — Pur- 
beck beds — New  fossil  Mammifer  found  at  Swanage — Dirt-bed  or  ancient  soil 
— Fossils  of  the  Purbeck  beds — Portland  stone  and  fossils — Lithographic  stone 
of  Solenhofen — Middle  Oolite — Coral  rag — Zoophytes — N"erinaean  limestone — 
Diceras  limestone — Oxford  clay,  Ammonites  and  Belemnites — Lower  Oolite, 
Crinoideans — Great  Oolite  and  Bradford  clay — Stonesfield  slate — Fossil  mam- 
malia, placental  and  marsupial — Kesemblance  to  an  Australian  fauna — North- 
amptonshire slates — Yorkshire  Oolitic  coal-field — Brora  coal — Fuller's  earth — 
Inferior  Oolite  and  fossils. 

IMMEDIATELY  below  the  Hastings  Sands  (the  inferior  member  of  the 
Wealden,  as  defined  in  the  18th  chapter),  we  find  in  Dorsetshire  another 
remarkable  freshwater  formation,  called  the  Purbeck,  because  it  was  first 
studied  in  the  sea-cliffs  of  the  peninsula  of  Purbeck  in  Dorsetshire.  These 
beds  were  formerly  grouped  with  the  Wealden,  but  some  organic  remains 
recently  discovered  in  certain  intercalated  marine  beds  show  that  the 
Purbeck  series  has  a  close  affinity  to  the  Oolitic  group,  of  which  it  may 
be  considered  as  the  newest  or  uppermost  member. 

In  England  generally,  and  in  the  greater  part  of  Europe,  both  the 
Wealden  and  Purbeck  beds  are  wanting,  and  the  marine  cretaceous  group 
is  followed  immediately,  in  the  descending  order,  by  another  series  called 
the  Jurassic.  In  this  term,  the  formations  commonly  designated  as  "  the 
Oolite  and  Lias"  are  included,  both  being  found  in  the  Jura  Mountains. 
The  Oolite  was  so  named  because  in  the  countries  where  it  was  first  ex- 
amined, the  limestones  belonging  to  it  had  an  oolitic  structure  (see  p.  12). 
These  rocks  occupy  in  England  a  zone  which  is  nearly  30  miles  in  aver- 
age breadth,  and  extends  across  the  island,  from  Yorkshire  in  the  north- 
east, to  Dorsetshire  in  the  southwest.  Their  mineral  characters  are  not 
uniform  throughout  this  region ;  but  the  following  are  the  names  of  the 
principal  subdivisions  observed  in  the  central  and  southeastern  parts  of 
England : 

OOLITE. 

(  a.  Purbeck  beds. 

Upper  •<  b.  Portland  stone  and  sand. 
^  c.  Kimmeridge  clay. 

•\fAA-t    <  <i  Coral  ra». 
MlddleU   Oxford  clay 

{/.  Cornbrash  and  Forest  marble. 
g.  Great  Oolite  and  Stonesfield  slate. 
h.  Fuller's  earth. 
i.  Inferior  Oolite. 

The  Lias  then  succeeds  to  the  Inferior  Oolite. 


292  PHYSICAL   GEOGRAPHY   OF  THE   OOLITE.  [Co.  XX 

The  Upper  oolitic  system  of  the  above  table  has  usually  the  Kimme- 
ridge  clay  for  its  base  ;  the  Middle  oolitic  system,  the  Oxford  clay.  The 
Lower  system  reposes  on  the  Lias,  an  argillo-calcareous  formation,  which 
some  include  in  the  Lower  Oolite,  but  which  will  be  treated  of  separately 
in  the  next  chapter.  Many  of  these  subdivisions  are  distinguished  by  pe- 
culiar organic  remains ;  and,  though  varying  in  thickness^  may  be  traced 
in  certain  directions  for  great  distances,  especially  if  we  compare  the  part 
of  England  to  which  the  above-mentioned  type  refers  with  the  northeast 
of  France  and  the  Jura  mountains  adjoining.  In  that  country,  distant 
above  400  geographical  miles,  the  analogy  to  the  accepted  English  type, 
notwithstanding  the  thinness  or  occasional  absence  of  the  clays,  is  more 
perfect  than  in  Yorkshire  or  Normandy. 

Physical  geography. — The  alternation,  on  a  grand  scale,  of  distinct  for- 
mations of  clay  and  limestone  has  caused  the  oolitic  and  liassic  series  to 
give  rise  to  some  marked  features  in  the  physical  outline  of  parts  of  Eng- 
land and  France.  Wide  valleys  can  usually  be  traced  throughout  the 
long  bands  of  country  where  the  argillaceous  strata  crop  out ;  and  be- 
tween these  valleys  the  limestones  are  observed,  composing  ranges  of  hills 
or  more  elevated  grounds.  These  ranges  terminate  abruptly  on  the  side  on 
which  the  several  clays  rise  up  from  beneath  the  calcareous  strata. 

The  annexed  cut  will  give  the  reader  an  idea  of  the  configuration  of 
the  surface  now  alluded  to,  such  as  may  be  seen  in  passing  from  London 
to  Cheltenham,  or  in  other  parallel  lines,  from  east  to  west,  in  the  southern 
part  of  England.  It  has  been  necessary,  however,  in  this  drawing,  greatly 

Fig.  833. 

Lower  Middle  Upper  London 

Oolite.  Oolite.  Oolite.  Chalk,  clay. 


Lias.  Oxford  Clay.  Kim.  clay.       Gault. 

to  exaggerate  the  inclination  of  the  beds,  and  the  height  of  the  several 
formations,  as  compared  to  their  horizontal  extent.  It  will  be  remarked, 
that  the  lines  of  cliff,  or  escarpment,  face  towards  the  west  in  the  great 
calcareous  eminences  formed  by  the  Chalk  and  the  Upper,  Middle,  and 
Lower  Oolites  ;  and  at  the  base  of  which  we  have  respectively  the  Gault, 
Kimmeridge  clay,  Oxford  clay,  and  Lias.  This  last  forms,  generally,  a 
broad  vale  at  the  foot  of  the  escarpment  of  inferior  oolite,  but  where  it 
acquires  considerable  thickness,  and  contains  solid  beds  of  marl-stone,  it 
occupies  the  lower  part  of  the  escarpment. 

The  external  outline  of  the  country  which  the  geologist  observes  in 
travelling  eastward  from  Paris  to  Metz  is  precisely  analogous,  and  is 
caused  by  a  similar  succession  of  rocks  intervening  between  the  tertiary 
strata  and  the  Lias ;  with  this  difference,  however,  that  the  escarpments 
of  Chalk,  Upper,  Middle,  and  Lower  Oolites  face  towards  the  east  instead 
of  the  west. 


CH.  XX.] 


UPPER   PURBECK. 


293 


The  Chalk  crops  out  from  beneath  the  tertiary  sands  and  clays  of  the 
Paris  basin,  near  Epernay,  and  the  Gault  from  beneath  the  Chalk  and 
Upper  Greensand'at  Clermont-en-Argonne  ;  and  passing  from  this  place 
by  Verdun  and  Etain  to  Metz,  -we  find  two  limestone  ranges,  with  inter- 
vening vales  of  clay,  precisely  resembling  those  of  southern  and  central 
England,  until  we  reach  the  great  plain  of  Lias  at  the  base  of  the  Inferior 
Oolite  at  Metz. 

It  is  evident,  therefore,  that  the  denuding  causes  have  acted  similarly 
over  an  area  several  hundred  miles  in  diameter,  sweeping  away  the  softer 
clays  more  extensively  than  the  limestones,  and  undermining  these  last  so 
as  to  cause  them  to  form  steep  cliffs  wherever  the  harder  calcareous  rock 
was  based  upon  a  more  yielding  and  destructible  clay. 

UPPER  OOLITE. 

Purbeck  beds  (a,  Tab.  p.  291). — These  strata,  which  we  class  as  the 
uppermost  member  of  the  Oolite,  are  of  limited  geographical  extent  in 
Europe,  as  already  stated,  but  they  acquire  importance,  when  we  consider 
the  succession  of  three  distinct  sets  of  fossil  remains  which  they  contain. 
Such  repeated  changes  in  organic  life  must  have  reference  to  the  history 
of  a  vast  lapse  of  ages.  The  Purbeck  beds  are  finely  exposed  to  view  in 
Durdlestone  Bay,  near  Swanage,  Dorsetshire,  and  at  Lulworth  Cove  and 
the  neighboring  bays  between  Weymouth  and  Swanage.  At  Meup's 
Bay,  in  particular,  Professor  K  Forbes  examined  minutely  in  1850  the 
organic  remains  of  this  group,  displayed  in  a  continuous,  sea-cliff  section  ; 
and  he  added  largely  to  the  information  previously  supplied  in  the  works 
of  Messrs.  Webster,  Fitton,  De  la  Beche,  Buckland,  and  Mantell.  It  ap- 
pears from  these  researches  that  the  Upper,  Middle,  and  Lower  Purbecks 
are  each  marked  by  peculiar  species  of  organic  remains,  these  again  being 
different,  so  far  as  a  comparison  has  yet  been  instituted,  from  the  fossils  of 
the  overlying  Hastings  Sands  and  Weald  Clay.* 

Upper  Purbeck. — The  highest  of  the  three  divisions  is  purely  fresh- 
water, the  strata,  about  50  feet  in  thickness,  containing  shells  of  the 
genera  Paludina,  Physa,  Limnceus,  Planorbis,  Valvata,  Cyclas,  and 
Unio,  with  Cyprides  and  fish.  All  the  species  seem  peculiar,  and  among 
these  the  Cyprides  are  very  abundant  and  characteristic.  (See  figs. 
334,  a,  6,  c.) 

Fig.  334, 


Cyprides  from  the  Upper  Purbecks. 
a.  Cypris gittoafiiE. Forbes.  &.  Cypris tuberculala, HForbes.  c.  Cypris legumintOa,  RForbei, 


*  "On  the  Dorsetshire  Purbecks,"  by  Prof.  E.  Forbes,  Brit  Assoc.  Ediab.  1850. 


294 


MIDDLE  PURBECK. 


[On.  XX. 


The  stone  called  "  Purbeck  marble,"  formerly  much  used  in  ornamental 
architecture  in  the  old  English  cathedrals  of  the  southern  counties,  is  ex- 
clusively procured  from  this  dirision. 

Middle  Purbeck. — Next  in  succession  is  the  Middle  Purbeck,  about  30 
feet  thick,  the  uppermost  part  of  which  consists  of  freshwater  limestone, 
with  cyprides,  turtles,  and  fish,  of  different  species  from  those  in  the  pre- 
ceding strata.  Below  the  limestone  are  brackish-water  beds  full  of 
Cyrena,  and  traversed  by  bands  abounding  in  Corbula  and  Melania. 
These  are  based  on  a  purely  marine  deposit,  with  Pecten,  Modiola, 
Avicula,  Thracia,  all  undescribed  shells.  Below  this,  again,  come  lime- 
stones and  shales,  partly  of  brackish  and  partly  of  freshwater  origin,  in 
which  many  fish,  especially  species  of  Lepidotus  and  Microdon  radiatus, 
are  found,  and  a  crocodilian  reptile  named  Macrorhyncus.  Among  the 
mollusks,  a  remarkable  ribbed  Melania,  of  the  section  Chilina,  occurs. 

Immediately  below  is  the  great  and  conspicuous  stratum,  12  feet  thick, 
long  familiar  to  geologists  under  the  local  name  of  "  Cinder-bed,"  formed 
of  a  vast  accumulation  of  shells  of  Ostrea  distorta  (fig.  335).  In  the 
uppermost  part  of  this  bed  Professor  Forbes  discovered  the  first  echino- 
denn  (fig.  336)  as  yet  known  in  the  Purbeck  series,  a  species  of  Hemici- 
daris,  a  genus  characteristic  of  the  Oolitic  period,  and  scarcely,  if  at  all, 
distinguishable  from  a  previously  known  oolitic  species.  It  was  accom- 


Fig.  335. 


Fig.  836. 


Ostrea  distorta. 
Cinder-bed,  Middle  Purbeck. 


Hemioidaris  Purbecfcensis.  E.  Forbes. 
Middle  Purbeck. 


panied  by  a  species  of  Perna.     Below  the  Cinder-bed  freshwater  strata 
are  again  seen,  filled  in  many  places  with  species  of  Cypris  (fig.  337, 


Cyprides  from  the  Middle  Purbecks. 

a.  Cypris  striato-punctata,  E.  Forbes.      6.  Cypris  fasciculata,  E.  Forbes. 
c.  Cypris  granulata,  Sow. 

a,  b,   c),   and   with   Valvata,  Paludina,  Planorbis,  Limnceus,  Physa 
(fig.  338),  and  Cydas,  all  different  from  any  occurring  higher  in  the 


CH.  XX.]  FOSSILS   OF  THE   MIDDLE   PUKBECK.  295 

series.  It  will  be  seen  that  Cypris  fasciculata  (fig. 
337,  b)  has  tubercles  at  the  end  only  of  each  valve,  a 
character  by  which  it  can  be  immediately  recognized.  In 
fact,  these  minute  crustaceans,  almost  as  frequent  in  some 
of  the  shales  as  plates  of  mica  in  a  micaceous  sandstone, 
enable  geologists  at  once  to  identify  the  Middle  Purbeck 
in  places  far  from  the  Dorsetshire  cliffs,  as,  for  example,  in 
the  Vale  of  Wardour,  in  Wiltshire.  Thick  siliceous  beds  Purbeck. 
of  chert  occur  in  the  Middle  Purbeck  filled  with  mollusca  and  cyprides  ot 
the  genera  already  enumerated,  in  a  beautiful  state  of  preservation,  often 
converted  into  chalcedony.  Among  these  Professor  Forbes  met  with 
gyrogonites  (the  spore-vessels  of  Charce),  plants  never  until  1851  discov- 
ered in  rocks  older  than  Eocene.  In  a  bed  of  this  series,  about  20  feet 
below  the  "  Cinder,"  Mr.  W.  K.  Brodie  has  lately  foond  (1854),  in  Dur- 
dlestone  Bay,  portions  of  several  small  jaws  with  teeth,  which  Professor 
Owen,  after  clearing  away  the  matrix,  recognized  as  belonging  to  a  small 
mammifer  of  the  insectivorous  class.  The  teeth  with  pointed  cusps  re- 
semble in  some  degree  those  of  the  Cape  Mole  ( Chrysochlora  aurea) ; 
but  the  number  of  the  molar  teeth  (at  least  ten  in  each  ramus  of  the 
lower  jaw)  accords  with  that  in  the  extinct  Thylacotherium  of  the  Stones- 
field  Oolite  (see  below,  Chap.  XX.).  This  newly-found  quadruped,  there- 
fore, seems  to  have  been  more  closely  allied  in  its  dentition  to  the 
Thylacotherium  than  to  any  existing  insectivorous  type.  As  in  Thylaco- 
therium, the  angular  process  of  the  jaw  is  not  bent  inwards,  an  osteologi- 
cal  peculiarity  confined  to  the  marsupial  tribes  (see  Chap.  XX.),  and 
Professor  Owen  therefore  refers  the  Spalatotherium  to  the  placental  or 
ordinary  class  of  monodelphous  mammalia. 

In  a  former  edition  of  this  work  (1852),  after  alluding  to  the  discovery 
of  numerous  insects  and  air-breathing  mollusca  in  the  "  Purbeck,"  I  re- 
marked that,  although  no  mammalia  had  then  been  found,  "  it  was  too 
soon  to  infer  their  non-existence  on  mere  negative  evidence."  The 
scarcity  of  the  remains  of  warm-blooded  quadrupeds  in  Oolitic  rocks,  and 
the  fact  of  none  having  yet  been  met  with  in  deposits  of  the  Cretaceous 
era,  may  imply  that  there  were  few  mammalia  then  living,  and  their 
limited  numbers  may  possibly  have  some  connection  with  the  enormous 
development  of  reptile  life  in  all  Secondary  periods,  as  compared  to  Ter- 
tiary or  Recent  times.  If  so,  the  phenomenon  has  at  least  no  relation  to 
an  incipient  or  immature  condition  of  the  planet,  as  some  have  imagined. 
for,  so  far  from  being  characteristic  of  primary  or  even  older  secondary 
times,  it  belongs  to  the  Maestricht  chalk,  the  newest  subdivision  of  the 
cretaceous  series,  and  that  too  in  a  manner  even  more  marked  than  in 
the  older  oolitic  rocks.  Nevertheless  in  the  present  imperfect  state  of  our 
information  respecting  the  land-animals  of  the  Cretaceous  and  Jurassic 
periods,  exclusively  derived  from  marine  and  fluviatile  strata,  and  our 
total  ignorance  of  the  deposits  formed  in  lakes  and  caverns  at  the  same 
date,  it  would  be  premature  to  attempt  to  generalize  on  the  nature  of  so 
ancient  a  terrestrial  fauna. 


296 


LOWER  PUEBECK. 


[On.  XX 


Fig.  839. 


Beneath  the  freshwater  strata  last  described,  a  very  thin  band  o. 
greenish  shales,  with  marine  shells  and  impressions  of  leaves,  like  those 
of  a  large  Zostera,  succeeds,  forming  the  base  of  the  Middle  Purbeck. 

Lower  Purbeck. — Beneath  the  thin  marine  band  above  mentioned, 
purely  freshwater  marls  occur,  containing  species  of  Cypris  (fig.  339, 
a,  5),  Valvata,  and  Lymnceus,  dif- 
ferent from  those  of  the  Middle 
Purbeck.  This  is  the  beginning  a, 
of  the  inferior  division,  which  is 
about  80  feet  thick.  Below  the 
marls  are  seen  more  than  30  feet 
of  brackish- water  beds,  at  Meup's 

Bay,    abounding    in    a    species    of  Cyprldes  from  the  Lower  Purbecks. 

Serpula,  allied  to,  if  not   identical   a.  Cypris  Purleckensis,       &.  Cypris  punctata, 

with,  Serpula  coacervites,  found  in 

beds  of  the  same  age  in  Hanover.  There  are  also  shells  of  the  genus 
Rissoa  (of  the  subgenus  Hydroibia),  and  a  little  Cardium  of  the  sub 
genus  Protocardium,  in  the  same  beds,  together  with  Cypris.  Some 
of  the  cypris-bearing  shales  are  strangely  contorted  and  broken  up,  at 
the  west  end  of  the  Isle  of  Purbeck.  The  great  dirt-bed  or  vegetable 
soil  containing  the  roots  and  stools  of  Cycadece,  which  I  shall  presently 
describe,  underlies  these  marls,  and  rests  upon  the  lowest  freshwater 
limestone,  a  rock  about  8  feet  thick,  containing  Cyclas,  Valvata,  and 
Limnceus,  of  the  same  species  as  those  of  the  uppermost  part  of 
the  Lower  Purbeck,  or  above  the  dirt-bed.  The  freshwater  limestone 
in  its  turn  rests  upon  the  top  beds  of  the  Portland  stone,  which, 
although  it  contains  purely  marine  remains,  often  consists  of  a  rock 
quite  homogeneous  in  mineral  character  with  the  lowest  Purbeck 
limestone.* 

The  most  remarkable  of  all  the  varied  succession  of  beds  enumerated 
in  the  above  list,  is  that  called  by 
the  quarrymen  "the  dirt,"  or 
"  black  dirt,"  which  was  evidently 
an  ancient  vegetable  soil.  It  is 
from  12  to  18  inches  thick,  is  of 
a  dark  brown  or  black  color,  and 
contains  a  large  proportion  of 
earthy  lignite.  Through  it  are 
dispersed  rounded  fragments  of 
stone,  from  3  to  9  inches  in  diame- 
ter, in  such  numbers  that  it  almost 
deserves  the  name  of  gravel.  Many 
silicified  trunks  of  coniferous  trees,  and  the  remains  of  plants  allied  to 
Zamia  and  Cycas,  are  buried  in  this  dirt-bed  (see  figure  of  fossil  species, 
fig.  340,  and  of  living  Zamia,  fig.  341). 

*  Weston,  Geol.  Q.  J.,  vol.  viii.  p.  117. 


Fig.  840. 


Cycadeoidea  (Mantellia)  megalophylla, 
Buckland. 


CH.  XX.]  FOSSIL   FOREST   IN  ISLE   OF   PORTLAND.  297 

Fig.  341. 


Zamia  epiralis.    Southern  Australia. 

These  plants  must  have  become  fossil  on  the  spots  where  they  grew. 
The  stumps  of  the  trees  stand  erect  for  a  height  of  from  1  to  3  feet,  and 
even  in  one  instance  to  6  feet,  with  their  roots  attached  to  the  soil  at 
about  the  same  distances  from  one  another  as  the  trees  in  a  modern 
forest.*  The  carbonaceous  matter  is  most  abundant  immediately  around 
the  stumps,  and  round  the  remains  of  fossil  Cycadece.\ 

Besides  the  upright  stumps  above  mentioned,  the  dirt-bed  contains  the 
stems  of  silicified  trees  laid  prostrate.  These  are  partly  sunk  into  the 
black  earth,  and  partly  enveloped  by  a  calcareous  slate  which  covers  the 
dirt-bed.  The  fragments  of  the  prostrate  trees  are  rarely  more  than 
3  or  4  feet  in  length  ;  but  by  joining  many  of  them  together,  trunks  have 
been  restored,  having  a  length  from  the  root  to  the  branches  of  from 
20  to  23  feet,  the  stems  being  undivided  for  17  or  20  feet,  and  then 
forked.  The  diameter  of  these  near  the  roots  is  about  1  foot.  Root- 
shaped  cavities  were  observed  by  Professor  Henslow  to  descend  from  the 
bottom  of  the  dirt-bed  into  the  subjacent  freshwater  stone,  which,  though 
now  solid,  must  have  been  in  a  soft  and  penetrable  state  when  the 
trees  grew.J 

Fig.  842. 


freshwater  calcareous  slate. 


dirt-bed  and  ancient  forest 

lowest  freshwater  beds  of  the  Lower 
Purbeck. 

Portland  stone,  marine. 
Section  in  Isle  of  Portland,  Dorset    (Bnckland  and  De  la  Beche.) 

*  Mr.  Webster  first  noticed  the  erect  position  of  the  trees  and  described  the 
Dirt-bed. 

f  Fitton,  Geol.  Trans.,  Second  Series,  voL  iv.  pp.  220,  221. 

\  Buckland  and  De  la  Beche,  Geol.  Trans.,  Second  Series,  voL  iv.  p.  16.  Pro- 
fessor Forbes  has  ascertained  that  the  subjacent  rock  is  a  freshwater  limestone, 
and  not  a  portion  of  the  Portland  oolite,  as  was  previously  imagined. 


298 


FOSSIL  FOREST  IN  LULWORTH  COVE. 


[On.  XX. 


The  thin  layers  of  calcareous  slate  (fig.  342)  were  evidently  deposited 
tranquilly,  and  would  have  been  horizontal  but  for  the  protrusion  of  the 
stumps  of  the  trees,  around  the  top  of  each  of  which  they  form  hemispher- 
ical concretions. 

The  dirt-bed  is  by  no  means  confined  to  the  island  of  Portland,  where 
it  has  been  most  carefully  studied,  but  is  seen  in  the  same  relative  position 
in  the  cliffs  east  of  Lulworth  Cove,  in  Dorsetshire,  where,  as  the  strata 
have  been  disturbed,  and  are  now  inclined  at  an  angle  of  45°,  the  stumps 
of  the  trees  are  also  inclined  at  the  same  angle  in  an  opposite  direction — 
a  beautiful  illustration  of  a  change  in  the  position  of  beds  originally  hori- 
zontal (see  fig.  343).  Traces  of  the  dirt-bed  have  also  been  observed  by 


Fig.  843. 


freshwater  calcareous  slate, 
dirt-bed,  with  stools  of  trees. 


freshwater. 


Portland  stone,  marine. 


Section  in  cliff  east  of  Lulworth  Cove.    (Buckland  and  De  la  Beche.) 

Mr.  Fisher,  at  Ridgway;  by  Dr.  Buckland,  about  two  miles  north  of 
Thame,  in  Oxfordshire ;  and  by  Dr.  Fitton,  in  the  cliffs  in  the  Boulonnois, 
on  the  French  coast ;  but,  as  might  be  expected,  this  freshwater  deposit 
is  of  limited  extent  when  compared  to  most  marine  formations. 

From  the  facts  above  described,  we  may  infer,  first,  that  those  beds  of 
the  upper  Oolite,  called  "  the  Portland,"  which  are  full  of  marine  shells, 
were  overspread  with  fluviatile  mud,  which  became  dry  land,  and  cov- 
ered by  a  forest,  throughout  a  portion  of  the  space  now  occupied  by  the 
south  of  England,  the  climate  being  such  as  to  admit  the  growth  of  the 
Zamia  and  Cycas.  2dly.  This  land  at  length  sank  down  and  was  sub- 
merged with  its  forests  beneath  a  body  of  freshwater,  from  which  sedi- 
ment was  thrown  down  enveloping  fluviatile  shells.  3dly.  The  regular 
and  uniform  preservation  of  this  thin  bed  of  black  earth  over  a  distance 
of  many  miles,  shows  that  the  change  from  dry  land  to  the  state  of  a 
freshwater  lake  or  estuary,  was  not  accompanied  by  any  violent  denuda- 
tion, or  rush  of  water,  since  the  loose  black  earth,  together  with  the  trees 
which  lay  prostrate  on  its  surface,  must  inevitably  have  been  swept  away 
bad  any  such  violent  catastrophe  taken  place. 

The  dirt-bed  has  been  described  above  in  its  most  simple  form,  but 
in  some  sections  the  appearances  are  more  complicated.  The  forest  of 
the  dirt-bed  was  not  everywhere  the  first  vegetation  which  grew  in  this 
region.  Two  other  beds  of  carbonaceous  clay,  one  of  them  containing 
-Cycadew,  in  an  upright  position,  have  been  found  below  it,  and  one 


CH.  XX.] 


CHANGES  OF  MEDIUM. — PURBECK  BEDS. 


299 


above  it,  which  implies  other  oscillations  in  the  level  of  the  same  ground, 
and  its  alternate  occupation  by  land  and  water  more  than  once. 

m 

Table  showing  the  changes  of  medium  in  which  the  strata  were  formed, 
from  the  Portland  Stone  up  to  the  Lower  Greensand  inclusive,  in  the 
southeast  of  England  (beginning  with  the  lowest). 


Portland  Stone. 


Lower  Purbeck. 


3.  Marine 

.         Freshwater 

Marine 

Brackish 

•  Middle  Purbeck 

Marine 

Brackish 

Freshwater 

4.  Freshwater         Upper  Purbeck. 

6.  Freshwater     ) 

Brackish          >  Hastings  Sands. 

Freshwater      j 

6.  Freshwater         Wealden  Clay. 

7.  Marine                Lower  Greensand. 

1.  Marine 

2.  Freshwater 
Land 

Freshwater 
Land 

Freshwater 
Land  (Dirt-bed) 
Freshwater 
Land 
Brackish 
Freshwater 


The  annexed  tabular  view  will  enable  the  reader  to  take  in  at  a  glance 
the  successive  changes  from  sea  to  river,  and  from  river  to  sea,  or  from 
these  again  to  a  state  of  land,  which  have  occurred  in  this  part  of  Eng- 
land between  the  Oolitic  and  Cretaceous  periods.  That  there  have  been 
at  least  four  changes  in  the  species  of  testacea  during  the  deposition  of 
the  Wealden  and  Purbeck  beds,  seems  to  follow  from  the  observations 
recently  made  by  Prof,  Forbes,  so  that,  should  we  hereafter  find  the 
signs  of  many  more  alternate  occupations  of  the  same  area  by  different 
elements,  it  is  no  more  than  we  might  expect.  Even  during  a  small  part 
of  a  zoological  period,  not  sufficient  to  allow  time  for  many  species  to  die 
out,  we  find  that  the  same  area  has  been  laid  dry,  and  then  submerged, 
and  then  again  laid  dry,  as  in  the  deltas  of  the  Po  and  Ganges,  the  his- 
tory of  which  has  been  brought  to  light  by  Artesian  borings.*  We  also 
know  that  similar  revolutions  have  occurred  within  the  present  century 
(1819)  in  the  delta  of  the  Indus  in  Cutch,f  where  land  has  been  laid 
permanently  under  the  waters  both  of  the  river  and  sea,  without  its  soil 
or  shrubs  having  been  swept  away.  Even,  independently  of  any  vertical 
movements  of  the  ground,  we  see  in  the  principal  deltas,  such  as  that  of 
the  Mississippi,  that  the  sea  extends  its  salt  waters  annually  for  many 
months  over  considerable  spaces  which,  at  other  seasons,  are  occupied  by 
the  river  during  its  inundations. 

It  will  be  observed  that  the  division  of  the  Purbecks  into  upper,  middle, 
and  lower  has  been  made  by  Prof.  Forbes,  strictly  on  the  principle  of  the 
entire  distinctness  of  the  species  of  organic  remains  which  they  include. 
The  lines  of  demarcation  are  not  lines  of  disturbance,  nor  indicated  by 
any  striking  physical  characters  or  mineral  changes.  The  features  which 
attract  the  eye  in  the  Purbecks,  such  as  the  dirt-beds,  the  dislocated 
strata  at  Lulworth,  and  the  Cinder-bed,  do  not  indicate  any  breaks  in  the 


See  Principles  of  Geol.  9th  ed.  pp.  255-275. 


f  Ibid.  p.  460 


300  PORTLAND  STONE.  [On.  XX. 

distribution  of  organized  beings.  "  The  causes  which  led  to  a  complete 
change  of  life  three  times  during  the  deposition  of  the  freshwater  and 
brackish  strata  must,"  says  this  naturalist,  "  be  sought  for,  not  simply  in 
either  a  rapid  or  a  sudden  change  of  their  area  into  land  or  sea,  but  in 
the  great  lapse  of  time  which  intervened  between  the  epochs  of  deposition 
at  certain  periods  during  their  formation." 

Each  dirt-bed  may,  no  doubt,  be  the  memorial  of  many  thousand  years 
or  centuries,  because  we  find  that  2  or  3  feet  of  vegetable  soil  is  the  only 
monument  which  many  a  tropical  forest  has  left  of  its  existence  ever 
since  the  ground  on  which  it  now  stands  was  first  covered  with  its  shade. 
Yet,  even  if  we  imagine  the  fossil  soils  of  the  Lower  Purbeck  to  repre- 
sent as  many  ages,  we  need  not  expect  on  that  account  to  find  them 
constituting  the  lines  of  separation  between  successive  strata  character- 
ized by  different  zoological  types.  The  preservation  of  a  layer  of  vege- 
table soil,  when  in  the  act  of  being  submerged,  must  be  regarded  as 
a  rare  exception  to  a  general  rule.  It  is  of  so  perishable  a  nature, 
that  it  must  usually  be  carried  away  by  the  denuding  waves  or  currents 
of  the  sea  or  by  a  river ;  and  many  Purbeck  dirt-beds  were  probably 
formed  in  succession,  and  annihilated,  besides  those  few  which  now 
remain. 

The  plants  of  the  Purbeck  beds,  so  far  as  our  knowledge  extends  at 
present,  consist  chiefly  of  Ferns,  Coniferas  (fig.  344),  and  Cycadese  (fig. 
340),  without  any  exogens;  the  whole  more  allied 
to  the  Oolitic  than  to  the  Cretaceous  vegetation.  Fig.844 

The  vertebrate  and  invertebrate  animals  indicate, 
like  the  plants,  a  somewhat  nearer  relationship  to 
the  Oolitic  than  to  the  cretaceous  period.  Mr. 
Brodie  has  found  the  remains  of  beetles  and  several 
insects  of  the  homopterous  and  trichopterous  orders, 
some  of  which  now  live  on  plants,  while  others  are 
of  such  forms  as  hover  over  the  surface  of  our  present 

Cone  of  a  pine  from  the 
rivers.  Isle  of  purbock  (Fitton). 

Portland  Stone  and  Sand  (b,  Tab.  p.  291). — The 

Portland  stone  has  already  been  mentioned  as  forming  in  Dorsetshire  the 
foundation  on  which  the  freshwater  limestone  of  the  Lower  Purbeck  re- 
poses (see  p.  296).  It  supplies  the  well-known  building-stone  of  which 
St.  Paul's  and  so  many  of  the  principal  edifices  of  London  are  constructed. 
This  upper  member  rests  on  a  dense  bed  of  sand,  called  the  Portland 
sand,  containing  for  the  most  part  similar  marine  fossils,  below  which  is 
the  Kimmeridge  clay.  In  England  these  Upper  Oolite  formations  are 
almost  wholly  confined  to  the  southern  counties.  Corals  are  rare  in 
them,  although  one  species  is  found  plentifully  at  Tisbury,  Wiltshire,  in 
the  Portland  sand,  converted  into  flint  and  chert,  the  original  calcareous 
matter  being  replaced  by  silex  (fig.  345). 

The  Kimmeridge  clay  consists,  in  great  part,  of  a  bituminous  shale, 
sometimes  forming  an  impure  coal,  several  hundred  feet  in  thickness.  In 
some  places  in  Wiltshire  it  much  resembles  peat ;  and  the  bituminous 


CH.  XX.]  FOSSILS  OF  THE  PORTLAND  STONE.  301 

Fig.  345. 

Fig.  846. 


Isastrcea  oblong  a,  M.  Edw.  and  J.  Haime. 

As  seen  on  a  polished  slab  of  chert  from 

the  Portland  sand,  Tisbury. 


Fig.  347. 


Trigonia  gibbosa.    J  nat  size. 

a,  the  hinge. 
Portland  Stone,  Tisbury. 


Fig.  343. 


Cardium  dissimile.    £  nat  size. 
Portland  Stone. 


Ostrea  e&pansa. 
Portland  Sand. 


matter  may  have  been,  in  part  at  least,  derived  from  the  decomposition  of 
vegetables.  But  as  impressions  of  plants  are  rare  in  these  shales,  which 
contain  ammonites,  oysters,  and  other  marine  shells,  the  bitumen  may 
perhaps  be  of  animal  origin. 

Among  the  characteristic  fossils  may  be  mentioned  Cardium  striatu- 
lum  (fig.  349)  and  Ostrea  deltoidea  (fig.  350),  the  latter  found  in  the 
Kimmeridge  clay  throughout  England  and  the  north  of  France,  and  also 
in  Scotland,  near  Brora.  The  Gryphcea  virgula  (fig.  351),  also  met  with 


Fig.  349. 


Fig.  850. 


Fig.861. 


Cardium  stHatulum. 
Kimmeridge  clay,  Hartwell. 


Ostrea  dettoidea.  GryphoM  virgula. 

Upper  Oolite :  Kimmeridge  clay,    i  nat  size. 


in  the  same  clay  near  Oxford,  is  so  abundant  in  the  Upper  Oolite  of 
parts  of  France  as  to  have  caused  the  deposit  to  be  termed  "  marnes  a 
gryphees  virgules."  Near  Clennont,  in  Argonne,  a  few  leagues  from  St. 
Menehould,  where  these  indurated  marls  crop  out  from  beneath  the  Gault, 


302 


CORAL   RAG. 


[Cn.  XX. 


Fig.  352. 


Trigonellites  latus. 
Kimmeridge  clay. 


I  have  seen  them,  on  decomposing,  leave  the  surface  of  every  ploughed 
field  literally  strewed  over  with  this  fossil  oyster.  The 
Trigonellites  latus  '(Aptychus,  of  some  authors)  (fig. 
352)  is  also  widely  dispersed  through  this  clay.  The 
real  nature  of  the  shell,  of  which  there  are  many  spe- 
cies in  oolitic  rocks,  is  still  a  matter  of  conjecture.  Some 
are  of  opinion  that  the  two  plates  formed  the  gizzard  of 
a  cephalopod ;  for  the  living  Nautilus  has  a  gizzard  with 
horny  folds,  and  the  Bulla  is  well  known  to  possess  one  formed  of  calca- 
reous plates. 

The  celebrated  lithographic  stone  of  Solenhofen,  in  Bavaria,  belongs 
to  one  of  the  upper  divisions  of  the  oolite,  and  affords  a  remarkable  ex- 
ample of  the  variety  of  fossils  which  may  be  preserved  under  favorable 
circumstances,  and  what  delicate  impressions  of  the  tender  parts  of  cer- 
tain animals  and  plants  may  be  retained  where 
the  sediment  is  of  extreme  fineness.  Although 
the  number  of  testacea  in  this  slate  is  small,  and 
the  plants  few,  and  those  all  marine,  Count 
Miinster  had  determined  no  less  than  237  spe- 
cies of  fossils  when  I  saw  his  collection  in  1833  ; 
and  among  them  no  less  than  seven  species  of 
flying  lizards,  or  pterodactyls  (see  fig.  353),  six 
saurians,  three  tortoises,  sixty  species  of  fish, 
forty-six  of  Crustacea,  and  twenty-six  of  insects. 
These  insects,  among  which  is  a  libellula,  or 
dragon-fly,  must  have  been  blown  out  to  sea, 
probably  from  the  same  land  to  which  the  flying  Skeleton  of  Pterodactyl™ 

.       ,-L  *  crass^rostns. 

lizards,  and  other  contemporaneous  reptiles,  re-  Oolite  of  Pappcnheim,  near  So- 

lenhofen. 

sorted. 


Fig.  363. 


MIDDLE    OOLITE. 


Coral  Rag. — One  of  the  limestones  of  the  Middle  Oolite  has  been 
called  the  "  Coral  Rag,"  because  it  consists,  in  part,  of  continuous  beds 
of  petrified  corals,  for  the  most  part  retaining  the  position  in  which  they 
grew  at  the  bottom  of  the  sea.  In  their  forms,  they  more  frequently 
resemble  the  reef-building  poliparia  of  the  Pacific  than  do  the  corals  of 
any  other  member  of  the  Oolite.  They  belong  chiefly  to  the  genera 
Thecosmilia  (fig.  354),  Protoseris,  and  Thamnastrcea,  and  sometimes 
form  masses  of  coral  15  feet  thick.  In  the  annexed  figure  of  a  Tham- 
nastrcea  (fig.  355),  from  this  formation,  it  will  be  seen  that  the  cup- 
shaped  cavities  are  deepest  on  the  right-hand  side,  and  that  they  grow 
more  and  more  shallow,  until  those  on  the  left  side  are  nearly  filled  up. 
The  last-mentioned  stars  are  supposed  to  represent  a  perfected  condition, 
and  the  others  an  immature  state.  These  coralline  strata  extend  through 
the  calcareous  hills  of  the  1ST.  W.  of  Berkshire,  and  north  of  Wilts,  and 


CH.  XX.] 


Fig.  854. 


CORALS  OF  THE   OOLITE. 
Corals  of  the  Coral  Bag. 


303 


Fig.  855. 


Thecosmilia  anmtlaris,  Milne  Edw.  and  J.  Haime. 
Coral  rag,  Steeple  Ashton. 


Thamnastrcea. 
Coral  rag,  Steeple  Ashton. 


again  recur  inYorkshire,  near  Scarborough.   The  Ostrea  gregarea  (fig.  356) 
is  very  characteristic  of  the  formation  in  England  and  on  the  continent 

One  of  the  limestones  of  the  Jura,  referred  to  the  age  of  the  English 
coral  rag,  has  been  called  "  Nerinaean  limestone"  (Calcaire  a  Nerinees) 
by  M.  Thirria ;  Nerincea  being  an  extinct  genus  of  univalve  shells,  much 
resembling  the  Cerithium  in  external  form.  The  annexed  section  (fig.  357) 
shows  the  curious  form  of  the  hollow  part  of  each  whorl,  and  also  the 
perforation  which  passes  up  the  middle  of  the  columella.  N.  Goodhallii 


Fig.  857. 


Fig.  358. 


Fig. 


Ostrea  gregarea. 
Coral  rag,  Steeple  Ashton. 


Nerincea  hieroglyphica. 
Coral  rag. 


Nerincea  Goodhallii,  Fitton. 
Coral  rag,  Weymouth.    £  nat  size. 


(fig.  358)  is  another  English  species  of  the  same  genus,  from  a  formation 
which  seems  to  form  a  passage  from  the  Kimmeridge  clay  to  the  coral 
rag.* 

A  division  of  the  oolite  in  the  Alps,  regarded  by  most  geologists  as 
coeval  with  the  English  coral  rag,  has  been  often  named  "  Calcaire  a  Di- 
cerates,"  or  "  Diceras  limestone,"  from  its  containing  abundantly  a  bivalve 
shell  (see  fig.  359)  of  a  genus  allied  to  the  Chama. 

*  Fitton,  Geol.  Trans.,  Second  Series,  vol.  iv.  pi.  23,  fig.  12. 


304: 


FOSSILS  OF  OXFOKD   CLAY. 

Fig.  860. 

<m 

Fig  859. 


[Cn.  XX, 


Cast  of  Diceras  arietina. 
Coral  rag,  France. 


Cidaris  coronata. 
Coral  rag. 


Oxford  Clay. — The  coralline  limestone,  or  "  coral  rag,"  above  de- 
scribed, and  the  accompanying  sandy  beds,  called  "  calcareous  grits"  of 
the  Middle  Oolite,  rests  on  a  thick  bed  of  clay,  called  the  Oxford  clay, 
sometimes  not  less  than  500  feet  thick.  In  this  there  are  no  corals,  but 
great  abundance  of  cephalopoda  of  the  genera  Ammonite  and  Belemnite. 
(Figs.  361, 362.)  In  some  of  the  clay  of  very  fine  texture  ammonites  are 

Fig.  861. 


Belemnites  hastatus.    Oxford  Clay. 

very  perfect,  although  somewhat  compressed,  and  are  seen  to  be  furnished 
on  each  side  of  the  aperture  with  a  single  horn-like  projection  (see  fig. 
362).  These  were  discovered  in  the  cuttings  of  the  Great  "Western 
Railway,  near  Chippenham,  in  1841,  and  have  been  described  by  Mr. 
Pratt.* 

Fig.  3C2. 


Ammonites  Jason,  Eeinecke.    Syn.    A.  Elizabeths,  Pratt. 
Oxford  clay,  Christian  Malford,  Wiltshire. 


S.  P.  Pratt,  Annals  of  Nat.  Hist.  November,  1841. 


On.  XX.] 
Fig. 


LOWER   OOLITE. 


305 


Bdemnites  Puzosianus, 

D'Orb. 
Oxford  Clay,  Christian 

Malford. 

a,  a.  Projecting  processes  of 
the  shell  or  phragmo- 
cone. 

Z>,  c.  Broken  exterior  of  a 
conical  shell  called 
the  phragmoconc, 
•which  is  chambered 
•within,  or  composed 
of  a  series  of  shallow 
concave  shells  pierced 
by  a  siph  ancle. 
o,  <?.  The  guard  or  osselet, 
•which  is  commonly 
called  the  belemnite. 


Similar  elongated  processes  have  been  also  ob 
served  to  extend  from  the  shells  of  some  belem- 
nites  discovered  by  Dr.  Mantell  in  the  same  clay 
(see  fig.  363),  \vho,  by  the  aid  of  this  and  other 
specimens,  has  been  able  to  throw  much  light  on 
the  structure  of  this  singular  extinct  form  of 
cuttle-fish.* 

LOWER  OOLITE. 

Cornbrash  and  Forest  Marble. — The  upper 
division  of  this  series,  which  is  more  exten- 
sive than  the  preceding  or  Middle  Oolite, 
is  called  in  England  the  Cornbrash.  It  con- 
sists of  clays  and  calcareous  sandstones,  which 
pass  downwards  into  the  Forest  Marble,  an 
argillaceous  limestone,  abc:inding  in  marine 
fossils.  In  some  places,  as  at  Bradford,  this 
limestone  is  replaced  by  a  mass  of  clay.  The 
sandstones  of  the  Forest  Marble  of  "Wiltshire  are 
often  ripple-marked  and  filled  with  fragments  of 
broken  shells  and  pieces  of  drift-wood,  having 
evidently  been  formed  on  a  coast.  Rippled  slabs 
of  fissile  oolite  are  used  for  roofing,  and  have 
been  traced  over  a  broad  band  of  country  from 
Bradford,  in  Wilts,  to  Tetbury,  in  Gloucestershire. 
These  calcareous  tile-stones  are  separated  from 
each  other  by  thin  seams  of  clay,  which  have 
been  deposited  upon  them,  and  have  taken  their 
form,  preserving  the  undulating  ridges  and  fur- 
rows of  the  sand  in  such  complete  integrity,  that 
the  impressions  of  small  footsteps,  apparently  of 
crabs,  which  walked  over  the  soft  wet  sands,  are 
still  visible.  In  the  same  stone  the  claws  of 
crabs,  fragments  of  echini,  and  other  signs  of  a 
neighboring  beach  are  observed.f 

Great  Oolite. — Although  the  name  of  coral- 
rag  has  been  appropriated,  as  we  have  seen,  to  a 
member  of  the  Upper  Oolite  before  described, 
some  portions  of  the  Lower  Oolite  are  equally 
entitled  in  many  places  to  be  called  coralline 
limestones.  Thus  the  Great  Oolite  near  Bath 
contains  various  corals,  among  which  the  Euno- 
mia  radiata  (fig.  364  is  very  conspicuous,  single 
individuals  forming  masses  several  feet  in  diam- 

See  Phil.  Trans.  1850,  p.  393. 
P.  Scrope,  Geol.  Proceed.  March,  1831. 
20 


306 


BRADFORD   ENCRINITES. 
Fig.  364. 


[CH.  XX, 


Eunomia  radiata,  Lamouroux.    (Calamophyttia,  Milne  Edw.) 

a.  Section  transverse  to  the  tubes. 

b.  Vertical  section,  showing  the  radiation  of  the  tubes. 

c.  Portion  of  interior  of  tubes  magnified,  showing  striated  surface. 

eter ;  and  having  probably  required,  like  the  large  existing  brain-corai 
(Meandrina)  of  the  tropics,  many  centuries  before  their  growth  was 
completed. 

Different  species  of  Crinoideans,  or  stone-lilies,  are  also  common  in 
the  same  rocks  with  corals ;  and,  like  them,  must  have  enjoyed  a  firm 
bottom,  where  their  root,  or  base  of  attachment,  remain.ed  undisturbed 
for  years  (c,  fig.  365).  Such  fossils,  therefore,  are  almost  confined  to 

Fig.  365. 


Apiocrinites  rotundus,  or  Pear  Encrinite ;  Miller.    Fossil  at  Bradford,  Wilts. 
a.  Stem  of  Apiocrinites,  and  one  of  the  articulations,  natural  size. 


&.  Section  at  Bradford  of  great  oolite  and  overlying  clay,  containing  the  fossil  encrinites.  See  text. 
c.  Three  perfect  individuals  of  Apiocrinites,  represented  as  they  grew  on  the  surface  of  the  Great 


Oolite. 
(I.  Body  of  the  Apiocrinites  rotundus. 


the  limestones  ;  but  an  exception  occurs  at  Bradford,  near  Bath,  where 
they  are  enveloped  in  clay.  In  this  case,  however,  it  appears  that  the 
solid  upper  surface  of  the  "  Great  Oolite"  had  supported,  for  a  time,  a 
thick  submarine  forest  of  these  beautiful  zoophytes,  until  the  clear  and 
still  water  was  invaded  by  a  current  charged  with  mud,  which  threw 
down  the  stone-lilies,  and  broke  most  of  their  stems  short  off  near  the 
point  of  attachment.  The  stumps  still  remain  in  their  original  position ; 
but  the  numerous  articulations  once  composing  the  stem,  arms,  and  body 
of  the  zoophyte,  were  scattered  at  random  through  the  argillaceous  de- 


Cn.  XX.]  PECULIAR  FOSSILS.  SOT 

posit  in  which  some  now  lie  prostrate.  These  appearances  are  lepre- 
sented  in  the  section  6,  fig.  365,  where  the  darker  strata  represent  the 
Bradford  clay,  which  some  geologists  class  with  the  Forest  marble,  oth- 
ers with  the  Great  Oolite.  The  upper  surface  of  the  calcareous  stone 
below  is  completely  incrusted  over  with  a  continuous  pavement,  formed 
by  the  stony  roots  or  attachments  of  the  Crinoidea ;  and  besides  this  evi- 
dence of  the  length  of  time  they  had  lived  on  the  spot,  we  find  great 
numbers  of  single  joints,  or  circular  plates  of  ihe  stem  and  body  of  the 
encrinite,  covered^  over  with  serpulce.  Now  these  serpulce  could  only 
have  begun  to  grow  after  the  death  of  some  of  the  stone-lilies,  parts  of 
whose  skeletons  had  been  strewed  over  the  floor  of  the  ocean  before  the 
irruption  of  argillaceous  mud.  In  some  instances  we  find  that,  after  the 
parasitic  serpulce  were  full  grown,  they  had  become  incrusted  over  with 
a  bryozoan,  called  Bercnicca  diluviana  ;  and  many  generations  of  these 
mollusks  had  succeeded  each  other  in  the  pure  water  before  they  became 
fossil. 

Fig.  366. 


a.  Single  plate  or  articulation  of  an  Encrinite  overgrown  with  aerpula  and  bryozoa.    Natural 

size.    Bradford  clay. 
&.  Portion  of  the  same  magnified,  showing  the  bryozoan  Berenicea  diluviana  covering  one  of 

the  serpulce. 

We  may,  therefore,  perceive  distinctly  that,  as  the  pines  and  cyca- 
deous  plants  of  the  ancient  "  dirt  bed,"  or  fossil  forest,  of  the  Lower  Pur- 
beck  were  killed  by  submergence  under  fresh  water,  and  soon  buried 
beneath  muddy  sediment,  so  an  invasion  of  argillaceous  matter  put  a 
sudden  stop  to  the  growth  of  the  Bradford  Encrinites,  and  led  to  their 
preservation  in  marine  strata.* 

Such  differences  in  the  fossils  as  distinguish  the  calcareous  and  argil- 
laceous deposits  from  each  other,  would  be  described  by  naturalists  as 
arising  out  of  a  difference  in  the  stations  of  species  ;  but  besides  these, 
there  are  variations  in  the  fossils  of  the  higher,  middle,  and  lower  part 
of  the  oolitic  series,  which  must  be  ascribed  to  that  great  law  of  change 
in  organic  life  by  which  distinct  assemblages  of  species  have  been 
adapted,  at  successive  geological  periods,  to  the  varying  conditions  of 
the  habitable  surface.  In  a  single  district  it  is  difficult  to  decide  how 

*  For  a  fuller  account  of  these  Encrinites,  see  Buckland's  Bridgewater  Treatise, 
vol.  i.  p.  429. 


308 


STONESFIELD  SLATE. 


[On.  XX 


far  the  limitation  of  species  to  certain  minor  formations  has  been  due  to 
the  local  influence  of  stations,  or  how  far  it  has  been  caused  by  time  or 
the  creative  and  destroying  law  above  alluded  to.  But  we  recognize 
the  reality  of  the  last-mentioned  influence,  when  we  contrast  the  whole 
oolitic  series  of  England  with  that  of  parts  of  the  Jura,  Alps,  and  other 
distant  regions,  where  there  is  scarcely  any  lithological  resemblance; 
and  yet  some  of  the  same  fossils  remain  peculiar  in  each  country  to  the 
Upper,  Middle,  and  Lower  Oolite  formations  respectively.  Mr.  Thui;- 
man  has  shown  how  remarkably  this  fact  holds  true  in  the  Bernese 
Jura,  although  the  argillaceous  divisions,  so  conspicuous  in  England,  are 
feebly  represented  there,  and  some  entirely  wanting. 

The  Bradford  clay  above  alluded  to  is  sometimes  60  feet  thick,  but, 
in  many  places,  it  is  wanting ;  and,  in  others,  where  there  are  no  lime- 
stones, it  cannot  easily  be  separated  from  the  clays  of  xhe  overlying 
"  forest  marble"  and  underlying  "  fuller's  earth." 

The  calcareous  portion  of  the  Great  Oolite  consists  of  several  shelly 
limestones,  one  of  which,  called  the  Bath  Oolite,  is  much  celebrated  as  a 
building-stone.  In  parts  of  Gloucestershire,  especially  near  Minchin- 
hampton,  the  Great  Oolite,  says  Mr.  Lycett,  "  must  have  been  deposited 
in  a  shallow  sea,  where  strong  currents  prevailed,  for  there  are  frequent 
changes  in  the  mineral  character  of  the  deposit,  and  some  beds  exhibit 
false  stratification.  In  others,  heaps  of  broken  shells  are  mingled  with 
pebbles  of  rocks  foreign  to  the  neighborhood,  and  with  fragments  of 
abraded  madrepores,  dicotyledonous  wood,  and  crabs'  claws.  The  shelly 
strata,  also,  have  occasionally  suffered  denudation,  and  the  removed  por- 
tions have  been  replaced  by  clay."*  In  such  shallow-water  beds  shells  of 


Fig.  368. 


Fig.  367. 


Terebratida  digona. 
Nat.  size.    Bradford  clay. 


Fig.  370. 


Purpuroidea  nodulata.  £  nat.  size.    Cylindrites  acutus,  Sow. 
Great  Oolite,  Minchinhampton.  Syn.  Actceon  acutus. 

Great  Oolite,  Minchinhampton. 


Fig.  371. 


Fig.  872. 


Patella  rugosa.  Sow. 
Great  Oolite. 


Nerlia  costulata,  Desh.        fiimula  (Emarginula) 
Great  Oolite.  clathrata,  Sow.  Great  Oolit«. 


*  Lycett,  Geol.  Journ.  vol.  ir.  p.  183. 


CH.  XX.]  STONESFIELD  SLATE.  309 

the  genera  Patella,  Nerita,  Rimula,  and  Cylindrites  are  common  (see 
figs.  369  to  372)  ;  while  cephalopods  are  rare,  and,  instead  of  ammonites 
and  belemnites,-  numerous  genera  of  carnivorous  trachelipods  appear. 
Out  of  one  hundred  and  forty-two  species  of  univalves  obtained  from  the 
Minchinhampton  beds,  Mr.  Lycett  found  no  less  than  forty-one  to  be  car- 
nivorous. They  belong  principally  to  the  genera  Buccinum,  Pleurotoma, 
Rostellaria,  Murex,  Purpuroidea  (fig.  368),  and  FILSUS,  and  exhibit  a 
proportion  of  zoophagous  species  not  very  different  from  that  which  ob- 
tains in  warm  seas  of  the  recent  period.  These  chronological  results  are 
curious  and  unexpected,  since  it  was  imagined  that  ^e  might  look  in 
vain  for  the  carnivorous  trachelipods  in  rocks  of  such  h.gh  antiquity  as 
the  Great  Oolite,  and  it  was  a  received  doctrine  that  they  did  not  begin 
to  appear  in  considerable  numbers  till  the  Eocene  period,  when  those  two 
great  families  of  cephalopoda,  the  ammonites  and  belemnites,  had  become 
extinct. 

Stonesfield  slate. — The  slate  of  Stonesfield  has  been  shown  by  Mr. 
Lonsdale  to  lie  at  the  base  of  the  Great  Oolite.*  It  is  a  slightly 
oolitic  shelly  limestone,  forming  large  spheroidal  masses  imbedded  in 
sand,  only  6  feet  thick,  but  very  rich  in  organic  remains.  It  contains 
some  pebbles  of  a  rock  very  similar  to  itself,  and  which  may  be  portions 
of  the  deposit,  broken  up  on  a  shore  at  low  water  or  during  storms,  and 
redeposited.  The  remains  of  belemnites,  trigoniae,  and  other  marine 
shells,  with  fragments  of  wood,  are  common,  and  impressions  of  ferns, 
cycadece,  and  other  plants.  Several  insects,  also,  and,  among  the  rest, 
Fig.  3-73.  the  wing-covers  of  beetles  are  perfectly  preserved  (see  fig. 
373),  some  of  them  approaching  nearly  to  the  genus  JZupres- 
tis.\  The  remains,  also,  of  many  genera  of  reptiles,  such  as 
Pleiosaur,  Crocodile,  and  Pterodactyl,  have  been  discovered  in 
the  same  limestone. 

But  the  remarkable  fossils  for  which  the  Stonesfield  slate 
is  most  celebrated,  are  those  referred  to  the  mammiferous 
class.  The  student  should  be  reminded  that  in  all  the  rocks 
described  in  the  preceding  chapters  as  older  than  the  Eocene, 
no  bones  of  any  land  quadruped,  or  of  any  cetacean,  have 
6tonesfi«id.  been  discovered  until  the  Spalacotherium  of  the  Purbeck  beds 
came  to  light  in  1854  (see  above,  p.  295).  Yet  we  have  seen  that  ter- 
restrial plants  were  not  rare  in  the  lower  cretaceous  formation,  and  that 
in  the  Wealden  there  was  evidence  of  freshwater  sediment  on  a  large 
scale,  containing  various  plants,  and  even  ancient  vegetable  soils.  We 
had  also  in  the  same  Wealden  many  land  reptiles  and  winged  insects, 
which  render  the  absence  of  terrestrial  quadrupeds  the  more  striking. 
The  want,  however,  of  any  bones  of  whales,  seals,  dolphins,  and  other 
aquatic  mammalia,  whether  in  the  chalk  or  in  the  upper  or  middle 
oolite,  is  certainly  still  more  remarkable.  Formerly,  indeed,  a  bone 

*  Proceedings  Geol.  Soc.  voL  i  p.  414. 

f  See  Buckland's  Bridgewater  Treatise  ;  and  Brodie's  Fossil  Insects,  where  it 
is  suggested  that  these  elytra  may  belong  to  Prionvs, 


310 


FOSSILS  OF  THE   OOLITE. 


[Cii.  XX. 


from  the  great  oolite  of  Enstone,  near  Woodstock,  in  Oxfordshire,  was 
cited,  on  the  authority  of  Cuvier,  as  referable  to  this  class.  Dr.  Buckland, 
who  stated  this  in  his  Bridge  water  Treatise  (vol.  i.  p.  115),  had  the 
kindness  to  send  me  the  supposed  ulna  of  a  whale,  that  Professor  Owen 
might  examine  into  its  claims  to  be  considered  as  cetacean.  It  is  the 

Fig.  874. 


Bone  of  a  reptile,  formerly  supposed  to  be  the  ulna  of  a  Cetacean ;  from  the  Great  Oolite  of 
Enstone,  near  Woodstock. 

opinion  of  that  eminent  comparative  anatomist  that  it  cannot  have 
belonged  to  the  cetacea,  because  the  fore-arm  in  these  marine  mammalia 
is  invariably  much  flatter,  and  devoid  of  all  muscular  depressions  and 
ridges,  one  of  which  is  so  prominent  in  the  middle  of  this  bone,  rep- 
resented in  the  above  cut  (fig.  374).  In  saurians,  on  the  contrary,  such 
ridges  exist  for  the  attachment  of  muscles  ;  and  to  some  animal  of  that 
class  the  bone  is  probably  referable. 

These  observations  are  made  to  prepare  the  reader  to  appreciate  more 
justly  the  interest  felt  by  every  geologist  in  the  discovery  in  the  Stones- 
field  slate  of  no  less  than  seven  specimens  of  lower  jaws  of  mammiferous 
quadrupeds,  belonging  to  three  different  species  and  to  two  distinct 
genera,  for  which  the  names  of  Amphitherium  and  Phascolotherium 
have  been  adopted.  When  Cuvier  was  first  shown  one  of  these  fossils 
in  1818,  he  pronounced  it  to  belong  to  a  small  ferine  mammal,  with  a 
jaw  much  resembling  that  of  an  opossum,  but  differing  from  all  known 
ferine  genera,  in  the  great  number  of  the  molar  teeth,  of  which  it  had 
at  least  ten  in  a  row.  Since  that  period,  a  much  more  perfect  specimen 
of  the  same  fossil,  obtained  by  Dr.  Buckland  (see  fig.  375),  has  been 

Fig.  375. 
Natural  size. 


Amphitherium  Frevostii,  Cuv.  Sp.    Stonesfleld  slate. 
a.  Coronoid  process.  &.  Condyle.  c.  Angle  of  jaw.  d.  Double-fanged  molars 


CH.  XX.] 


OOLITIC   GROUP  AND   ITS   FOSSILS. 


311 


376- 


8late- 


examined  by  Prof.  Owen,  who  finds  that  the  jaw 
contained  on  the  whole  twelve  molar  teeth,  with 
the  socket  of  a  small  canine,  and  three  small 
incisors,  which  are  in  situ,  altogether  amount- 
ing  to  sixteen  teeth  on  each  side  of  the  lower 
jaw. 

The  only  question  which  could  be  raised  respecting  the  nature  of  these 
fossils  was,  whether  they  belonged  to  a  maminifer,  a  reptile,  or  a  fish. 
Now  on  this  head  the  osteologist  observes  that  each  of  the  seven  half 
jaws  is  composed  of  but  one  single  piece,  and  not  of  two  or  more  sepa- 
rate bones,  as  in  fishes  and  most  reptiles,  or  of  two  bones,  united  by  a 
suture,  as  in  some  few  species  belonging  to  those  classes.  The  condyle, 
moreover  (6,  fig.  375),  or  articular  surface,  by  which  the  lower  jaw  unites 
with  the  upper,  is  convex  in  the  Stonesfield  specimens,  and  not  concave 
as  in  fishes  and  reptiles.  The  coronoid  process  (a,  fig.  375)  is  well  de- 
veloped, whereas  it  is  wanting,  or  very  small,  in  the  inferior  classes  of  ver 
tebrata.  Lastly,  the  molar  teeth  in  the  Amphitherium  and  Phascolo- 
tkerium  have  complicated  crowns,  and  two  roots  (see  d,  fig.  375),  in- 
stead of  being  simple  and  with  single  fangs.* 

The  only  question,  therefore,  which  could  fairly  admit  of  controversy 
was  limited  to  this  point,  whether  the  fossil  mammalia  found  in  the 
lower  oolite  of  Oxfordshire  ought  to  be  referred  to  the  marsupial  quad- 
rupeds, or  to  the  ordinary  placental  series.  Cuvier  had  long  ago  pointed 
out  a  peculiarity  in  the  form  of  the  angular  process  (c,  figs.  380  and 
381)  of  the  lower  jaw,  as  a  character  of  the  genus  Didelphys  ;  and  Prof. 


Tupaia  Tana, 
Eight  ramus  of  lower  jaw, 

natural  size. 

A  recent  insectivorous  mammal  from 
Sumatra. 


Fig.  881. 


Part  of  lower  jaw  of  Tapaia  Tana; 

twice  natural  size. 
Fig.  289.  End  view  seen  from  behind,  showing 

the  very  slight  inflection  of  the  angle  at  c. 
Fig.  290.  Side  view  of  same. 


Part  of  lower  jaw  of  Didelphys  Azarae, ; 

recent,  Brazil.    Natural  size. 
Fig.  291.  End  view  seen  from  behind,  showing 

the  inflection  of  the  angle  of  the  jaw,  c,  a. 
Fig.  292.  Side  view  of  same. 


*  I  have  given  a  figure  in  the  Principles  of  Geology,  chap,  ix.,  of  another 
Stonesfield  specimen  of  Amphitherium  Prevostii,  in  which  the  sockets  and  roots 
of  the  teeth  are  finely  exposed. 


312  OOLITIC  GROUP  [OH.  XX 

Owen  has  since  established  its  generality  in  the  entire  marsupial  series. 
In  all  these  pouched  quadrupeds,  this  process  is  turned  inwards,  as  at  c  d, 
fig.  380,  in  the  Brazilian  opossum,  whereas  in  the  placental  series,  as  at  c, 
figs.  378  and  379,  there  is  an  almost  entire  absence  of  such  inflection. 
The  Tupaia  Tana  of  Sumatra  has  been  selected  by  my  friend  Mr.  Water- 
house  for  this  illustration,  because  that  small  insectivorous  quadruped 
bears  a. great  resemblance  to  those  of  the  Stonesfield  Amphitherium.  By 
clearing  away  the  matrix  from  the  specimen  of  Amphitherium  Prevostii 
above  represented  (fig.  375),  Prof.  Owen  ascertained  that  the  angular  pro- 
cess (c)  bent  inwards  in  a  slighter  degree  than  in  any  of  the  known  mar- 
supialia ;  in  short,  the  inflection  does  not  exceed  that  of  the  mole  or 
hedgehog.  This  fact  turns  the  scale  in  favor  of  its  affinities  to  the  placental 
insectivora.  Nevertheless,  the  Amphitherium  offers  some  points  of  approxi- 
mation in  its  osteology  to  the  marsupials,  especially  to  the  MyrmecoUus,  a 
small  insectivorous  quadruped  of  Australia,  which  has  nine  molars  on  each 
side  of  the  lower  jaw,  besides  a  canine  and  three  incisors.* 

Another  species  of  Amphitherium  has  been  found  at  Stonesfield  (fig. 
376,  p.  311),  which  differs  from  the  former  (fig.  375)  principally  in  being 
larger. 

The  second  mammiferous  genus  discovered  in  the  same  slates  was 
named  originally  by  Mr.  Broderip  Didelphys  BucJclandi  (see  fig.  382), 

Fig.  3S2. 


Phascolotherium  Bucklandi,  Broderip,  sp. 
a.  Natural  size.  &.  Molar  of  same  magnified. 

and  has  since  been  called  Phascolotherium  by  Owen.  It  manifests  a 
much  stronger  likeness  to  the  marsupials  in  the  general  form  of  the  jaw, 
and  in  the  extent  and  position  of  its  inflected  angle,  while  the  agreement 
with  the  living  genus  Didelphys  in  the  number  of  the  premolar  and  molar 
teeth  is  complete.f 

On  reviewing,  therefore,  the  whole  of  the  osteological  evidence,  it  will 
be  seen  that  we  have  every  reason  to  presume  that  the  Amplitherium 
and  Phascolotherium  of  Stonesfield  represent  both  the  placental  and  mar- 
supial classes  of  mammalia ;  and  if  so,  they  warn  us  in  a  most  emphatic 
manner,  not  to  found  rash  generalizations  respecting  the  non-existence  of 
certain  classes  of  animals  at  particular  periods  of  the  past  on  mere  nega- 
tive evidence.  The  singular  accident  of  our  having  as  yet  found  nothing 
but  the  lower  jaws  of  seven  individuals,  and  no  other  bones  of  their  skele- 
tons, is  alone  sufficient  to  demonstrate  the  fragmentary  manner  in  which 
the  memorials  of  an  ancient  terrestrial  fauna  are  handed  down  to  us. 

*  A  figure  of  this  recent  Myrmecoblus  will  be  found  in  the  Principles,  chap.  ix. 
f  Owen's  British  Fossil  Mammals,  p.  62. 


CH.  XX.]  AND   ITS  FOSSILS.  313 

We  can  scarcely  avoid  suspecting  that  the  two  genera  above  described 
may  have  borne  a  like  insignificant  proportion  to  the  entire  assemblage 
of  warm-blooded  quadrupeds  which  flourished  in  the  islands  of  the 
oolitic  sea. 

Prof.  Owen  has  remarked  that,  as  the  marsupial  genera,  to  which  the 
Phascolotherium  is  most  nearly  allied,  are  now  confined  to  New  South 
Wales  and  Van  Dieman's  Land,  so  also  is  it  in  the  Australian  seas,  that 
we   find   the    Cestracion,   a   cartilaginous   fish 
which  has  a  bony  palate,  allied  to  those  called 
Acrodus  (see  fig.  412,  p.  321)  and  Strophodus, 
so  common  in  the  oolite  and  lias.     In  the  same 
Australian  seas,  also,  near  the  shore,  we  find 
the  living  Trigonia,  a  genus  of  mollusca  so  fre- 
quently met  with  in  the  Stonesfield  slate.     So, 
also,  the  Araucarian  pines  are  now  abundant, 
together  with  ferns,  in  Australia  and  its  islands.     Portion  "^ 
as  they  were  in  Europe  in  the  oolitic  period.       focarya  magnified.  (Bnck- 

J  r  land  s  Bridgrw.  Treat  PI.  63.) 

Endogens  of  the  most  perfect  structure  are  met  inferior  Oolite,  Channouth, 
with  in  oolitic  rocks,  as,  for  example,  the  Podo- 

carya  of  Buckland,  a  fruit  allied  to  the  Pandanus,  found  in  the  Inferior 
Oolite  (see  fig.  383). 

The  Stonesfield  slate,  in  its  range  from  Oxfordshire  to  the  northeast,  is 
represented  by  flaggy  and  fissile  sandstones,  as  at  Collyweston  in  North- 
amptonshire, where,  according  to  the  researches  of  Messrs.  Ibbetson  and 
Morris,*  it  contains  many  shells,  such  as' Trigonia  angulata,  also  found 
at  Stonesfield.  But  the  Northamptonshire  strata  of  this  age  assume  a 
more  marine  character,  or  appear  at  least  to  have  been  formed  farther 
from  land.  They  inclose,  however,  some  fossil  ferns,  such  as  Pecopteris 
polypodioides,  of  species  common  to  the  oolites  of  the  Yorkshire  coast, 
where  rocks  of  this  age  put  on  all  the  aspect  of  a  true  coal-field ;  thin 
seams  of  coal  having  actually  been  worked  in  them  for  more  than  a 
century. 

In  the  northwest  of  Yorkshire,  the  formation  alluded  to  consists  of  an 
upper  and  a  lower  carbonaceous  shale,  abounding  in  impressions  of  plants, 
divided  by  a  limestone  considered  by  many  geologists  as  the  representa- 
tive of  the  Great  Oolite  ;  but  the  scarcity  of  marine  fossils  makes  all  com- 
parisons with  the  subdivisions  adopted  in  the  south  extremely  difficult 
A  rich  harvest  of  fossil  ferns  has  been  obtained  from  the  upper  carbona- 
ceous shales  and  sandstones  at  Gristhorpe,  near  Scarborough  (see  figs. 
384,  385).  The  lower  shales  are  well  exposed  in  the  sea-cliffs  at  Whitby, 
and  are  chiefly  characterized  by  ferns  and  cycadeae.  They  contain,  also, 
a  species  of  calamite,  and  a  fossil  called  Equisetum  columnare,  which 
maintains  an  upright  position  in  sandstone  strata  over  a  wide  area. 
Shells  of  Estheria  and  Uniot  collected  by  Mr.  Bean  from  these  Yorkshire 
coal-bearing  beds,  point  to  the  estuary  or  fluviatile  origin  of  the  deposit. 

*  Ibbetson  and  Morris,  Report  of  Brit.  Ass.,  1847,  p.  131 ;  and  Morris,  GeoL 
Journn  ix.  p.  334. 


314 


OOLITIC  GROUP 
Fig.  884. 


[CH.  XX. 


PteropJiyllum  comptum.    Syn.  Cycadites  comptus. 
Upper  sandstone  and  shale,  Gristhorpe,  near  Scarborough. 


Fig.  386. 


Hemitelites  Brmcnii,  Goepp. 
Syn.  Phlebopteris  contigua,  Lind.  &  Hutt. 

Upper  carbonaceous  strata,  Lower  Oolite,  Gristhorpe,  Yorkshire. 


At  Brora,  in  Sutherlandshire,  a  coal  formation,  probably  coeval  with 
the  above,  or  belonging  to  some  of  the  lower  divisions  of  the  Oolitic 
period,  has  been  mined  extensively  for  a  century  or  more.  It  affords  the 
thickest  stratum  of  pure  vegetable  matter  hitherto  detected  in  any  sec- 
ondary rock  in  England.  One  seam  of  coal  of  good  quality  has  been 
worked  3  j-  feet  thick,  and  there  are  several  feet  more  of  pyritous  coal 
resting  upon  it. 

Fuller's  Earth  (h,  Tab.  p.  291).— Between  the  Great 
and  Inferior  Oolite,  near  Bath,  an  argillaceous  deposit, 
called  "  the  fuller's  earth,"  occurs ;  but  it  is  wanting  in 
the  north  of  England.  It  abounds  in  the  small  oyster 
represented  in  fig.  386. 

Inferior  Oolite.— This  formation  consists  of  a  calcare- 
ous  freestone,  usually  of  small  thickness,  which  sometimes 
rests  upon,  or  is  replaced  by,  yellow  sands,  called  the  sands  of  the  Inferior 
Oolite.  These  last,  in  their  turn,  repose  upon  the  lias  in  the  south  and 
west  of  England.  Among  the  characteristic  shells  of  the  Inferior  Oolite, 
I  may  instance  Terebratula  fimbria  (fig.  387),  Rhynchonella  spinosa 
(fig.  388),  and  Pholadomya  fidicula  (fig.  389).  The  extinct  genus 
Pleurotomaria  is  also  a  form  very  common  in  this  division  as  well  as  in 
the  Oolitic  system  generally.  It  resembles  the  Trochus  in  form,  but  is 


AND   ITS  FOSSILS. 


Fig.  3SS. 


315 


Fig.  389. 


Terebratula fimbria.    EhynchoneUa  spinosa.    a.  PJwladomyafidicula.    %  nat.  size.  Inf.  Ool. 
Inferior  Oolite.  Inferior  Oolite.  &.  Heart-shaped  anterior  termination  of  the 

same. 


Fig.  391. 


Fig.  392. 


Pleurotomaria  granulata. 

Ferruginous  Oolite,  Normandy. 

Inferior  Oolite,  England. 


Pleurotomaria  omata,  Sow.  Sp. 
Inferior  Oolite. 


Disaster  ringens. 
Inf.  Ool.  Somersetshire. 


marked  by  a  deep  cleft  (a,  fig.  390,  and  fig.  391)  on  the  right  side  of  the 
mouth.  The  Dysaster  ringens  (fig.  392)  is  an  Echinoderm  common  to 
the  Inferior  Oolite  of  England  and  France,  as  are  the  three  Ammonites  of 
which  representations  are  here  given  (figs.  393,  394,  395). 

Fig.  893. 


Ammonites  Humphresianu*. 
Inferior  Oolite. 

As  illustrations  of  shells  having  a  great  vertical  range,  I  may  allude  to 
Trigonia  clavellata,  found  in  the  Upper  and  Inferior  Oolite,  and  T.  costata, 
common  to  the  Upper,  Middle,  and  Lower  Oolite ;  also  Ostrea  Marshii 
(fig.  396),  common  to  the  Cornbrash  of  Wilts  and  the  Inferior  Oolite  of 
Yorkshire;  and  Ammonites  striatulus  (fig.  397)  common  to  the  Inferior 
Oolite  and  Lias. 


316 


Fig.  394. 


LNFEKIOR  OOLITE. 
6 


Ammonites  margaritatus,  D'Orb.    Syn.  A.  StoJcesii,  Sow, 
Lias. 


Pig.  896. 


Ammonites  Brailcenridgii,  Sow. 

Great  Oolite,  Scarborough. 
Inf.  Ool.  Dundry;  Calvados;  &c. 


Fig.  397. 


Ostrea  MarsMi.    %  nat  size. 
Middle  and  Lower  Oolite. 


Ammonites  striatulus,  Sow. 

i  nat.  size. 
Inferior  Oolite  and  Lias. 


Such  facts  by  no  means  invalidate  the  general  rule,  that  certain  fossils 
are  good  chronological  tests  of  geological  periods ;  but  they  serve  to 
caution  us  against  attaching  too  much  importance  to  single  species,  some 
of  which  may  have  a  wider,  others  a  more  confined  vertical  range.  We 
have  before  seen  that,  in  the  successive  tertiary  formations,  there  are  spe- 
cies common  to  older  and  newer  groups,  yet  these  groups  are  distinguish- 
able from  one  another  by  a  comparison  of  the  whole  assemblage  of  fossil 
shells  proper  to  each. 


CH.  XXL]  MINERAL  CHARACTER  OF  THE   LIAS.  317 


CHAPTER  XXI. 
JURASSIC  GROUP — continued.     LIAS. 

Mineral  character  of  Lias — Name  of  Gryphite  limestone — Fossil  shells  and  fish — 
Radiata — Ichthyodorulites — Reptiles  of  the  Lias — Ichthyosaur  aud  Plesiosaur 
— Marine  Reptile  of  the  Galapagos  Islands — Sudden  destruction  and  burial  of 
fossil  animals  in  Lias — Fluvio-marine  beds  in  Gloucestershire,  and  insect  lime- 
stone— Fossil  plants — Origin  of  the  Oolite  and  Lias,  and  of  alternating  calca- 
reous and  argillaceous  formations — Oolitic  coal-field  of  Virginia,  in  the  United 
States. 

LIAS. — The  English  provincial  name  of  Lias  has  been  very  generally 
adopted  for  a  formation  of  argillaceous  limestone,  marl,  and  clay,  which 
forms  the  base  of  the  Oolite,  and  is  classed  by  many  geologists  as  part  of 
that  group.  They  pass,  indeed,  into  each  other  in  some  places,  as  near 
Bath,  a  sandy  marl  called  the  marlstone  of  the  Lias  being  interposed, 
and  partaking  of  the  mineral  characters  of  the  lias  and  the  inferior  oolite. 
These  last-mentioned  divisions  have  also  some  fossils  in  common,  such  as 
the  Avicula  incequivalvis  (fig.  398).  Nevertheless,  the  Lias  may  be 

Fig.  399. 

iiaR^///////^ 
Fig  398. 


Avicula  incequivalvis,  Sow.  Avicula  cygnipes,  Phil. 

Lower  Oolite.  Marlstone,  Gloucestershire ;  Lias,  Yorkshire. 

traced  throughout  a  great  part  of  Europe  as  a  separate  and  independent 
group,  of  considerable  thickness,  varying  from  500  to  1000  feet,  contain- 
ing many  peculiar  fossils,  and  having  a  very  uniform  lithological  aspect. 
Although  usually  conformable  to  the  oolite,  it  is  sometimes,  as  in  the 
Jura,  unconformable.  In  the  environs  of  Lons-le-Saulnier,  for  instance, 
in  the  department  of  Jura,  the  strata  of  lias  are  inclined  at  an  angle  of 
about  45°,  while  the  incumbent  oolitic  marls  are  horizontal. 

The  peculiar  aspect  which  is  most  characteristic  of  the  Lias  in  Eng- 
land, France,  and  Germany,  is  an  alternation  of  thin  beds  of  blue  or  gray 
limestone,  having  a  surface  which  becomes  light-brown  when  weathered, 


318  NAME   OF   "  GKYPHITE   LIMESTONE."  [On.  XXL 

these  beds  being  separated  by  dark-colored  narrow  argillaceous  partings, 
so  that  the  quarries  of  this  rock,  at  a  distance,  assume  a  striped  and 
riband-like  appearance.* 

The  Lias  comprises,  1,  the  Upper  Lias — thin  limestone  beds  with  clay 
and  shale ;  2,  the  Marlstone — a  coarse  shelly  limestone ;  and  3,  the 
Lower  Lias — consisting  of  limestone,  shells,  and  clay.  These  divisions 
have  certain  fossils  in  common,  and  in  some  places  pass  the  one  into  th£ 
other. 

Although  the  prevailing  color  of  the  limestone  of  this  formation  is 
blue,  yet  some  beds  of  the  lower  lias  are  of  a  yeLowish  white  color,  and 
have  been  called  white  lias.  In  some  parts  of  France,  near  the  Vos^es 

1  /  o 

mountains,  and  in  Luxembourg,  M.  E.  de  Beaumont  has  shown  that  the 
lias  containing  GrypJicea  arcuata,  Plagiostoma  giganteum  (see  fig.  400), 
and  other  characteristic  fossils,  becomes  arenaceous ;  and  around  the  Hartz, 
in  Westphalia  and  Bavaria,  the  inferior  parts  of  the  lias  are  sandy,  and 
sometimes  afford  a  building-stone. 

The  name  of  Gryphite  limestone  has  sometimes  been  applied  to  the 
lias,  in  consequence  of  the  great  number  of  shells  which  it  contains  of  a 

Fig.  400. 


Fig.  401. 


GrypTiwa  incurva,  Sow. 

(G.  arcuata,  Lam.) 

Lias. 


Plagiostoma  (Lima)  giganteum^  Sow. 
Inf.  Ool.  and  Lias. 

species  of  oyster,  or  Gryphcea  (fig.  401 ;  see,  also,  fig.  30,  p.  29).  A 
large  heavy  shell  called  Hippopodium  (fig.  402),  allied  to  Isocardia,  is 
also  characteristic  of  the  lower  lias  shales.  The  Lias  formation  is  also 
remarkable  for  being  the  oldest  of  the  secondary  rocks  in  which  brachi- 
opoda  of  the  genera  Spirifer  and  Leptcena  (figs.  403,  404)  occur :  no 
less  than  nine  species  of  Spirifers  are  enumerated  by  Mr.  Davidson  as 
belonging  to  the  lias.  These  palliobranchiate  mollusca  predominate 
greatly  in  strata  older  than  the  trias ;  but,  so  far  as  we  yet  know,  they 
did  not  survive  the  liassic  epoch.  The  marine  beds  of  the  lias  also  abound 
in  cephalopoda  of  the  genera  Belemnites,  Nautilus,  and  Ammonites  (see 
figs.  405,  406,  407). 

Among  the  Crinoids  or  Stone-Lilies  of  the  Lias,  Pentacrinus  Briareus 

*  Conyb.  and  Phil.  p.  261. 


CH.  XXL]  FOSSILS  OF  THE  LIAS. 

Fig.  402.  Fig.  403. 


319 


Spirifer  WalcotU,  Sow 
Lower  Lias. 


Hippopodium  ponderosum,  Sow. 
\  diam.    Lias,  Cheltenham. 


Fig.  405. 


Nautilus  truncatus.    Lias. 
Fig.  407. 


Leptcena  Moorei,  Dav. 
Upper  Lias,  Ilmtnster. 


Fig.  406. 


Ammonites  Nodotianu*  f 

A.  striatulus.  Sow. 

Lias. 


Ammonites  Bifrons,  Brug. 
A.  WalcotU,  Sow. 
Upper  Lias  shales. 


(fig.  408)  is  conspicuous.  Of  Ophioderma  Egertoni  (fig.  409),  referable 
to  the  OpkiurcB  of  Muller,  perfect  specimens  have  been  met  with  in  the 
marlstone  beds  of  Dorset  and  Yorkshire. 


320 


FOSSILS   OF  THE  LIAS. 


.  XXL 


Fig.  408. 


Fig.  409. 


Extracrinus  Briareus.    £  nat.  size. 
(Body,  arms,  and  part  of  stem.) 
Lias,  Lyme  Kegis. 


OpModerma  Egertoni,  E.  Forbes. 
Lias  Marlstone,  Lyme  Eegis. 


The  Extracrinus  Briareus  (removed  by  Major  Austin  from  Pentacri- 
nus  on  account  of  generic  differences)  occurs  in  tangled  masses,  forming 
thin  beds  of  considerable  extent,  in  the  Lias  of  Dorset,  Gloucestershire, 
and  Yorkshire.  The  remains  are  often  highly  charged  with  pyrites. 
This  Crinoid,  with  its  innumerable  tentacular  arms,  appears  to  have  been 
frequently  attached  to  the  drift-wood  of  the  liassic  sea,  in  the  same  man- 
ner as  Barnacles  float  about  at  the  present  day.  There  is  another  species 
of  Extracrinus  and  several  of  Pentacrinus  in  the  lias ;  and  the  latter 
genus  is  found  in  nearly  all  the  formations  from  the  lias  to  the  London 
clay  inclusive.  It  is  represented  in  the  present  seas  by  the  delicate  and 
rare  Pentacrinus  Caput-medusce  of  the  Antilles ;  and  this  indeed  is 
perhaps  the  only  surviving  member  of  the  great  and  ancient  family  of 
the  Crinoids,  so  widely  represented  throughout  the  older  formations  by 
the  genera  Taxocrinus,  Actinocrinus,  Cyathocrinus,  Encrinus,  Apiocri- 
nus,  and  many  others. 

The  fossil  fish  re-  «  Fi?-  41°- 

semble  generically 
those  of  the  oolite, 
belonging  all,  ac- 
cording to  M,  Agas- 
siz,  to  extinct  gen- 
era, and  differing 
for  the  most  part 
from  the  ichthyolites 
of  the  Cretaceous  pe- 


Scales  of  Lepidotus  gigas. 
a.  Two  of  the  scales  detached. 


CH.  XXL] 


FOSSILS   OF  THE   LIAS. 


321 


riod.  Among  them  is  a  species  of  Lepidotus  (L.  yigas,  Agas.),  fig.  410, 
which  is  found  in  the  Has  of  England,  France,  and  Germany.*  This 
genus  was  before  mentioned  (p.  262)  as  occurring  in  the  Wealden,  and 
is  supposed  to  have  frequented  both  rivers  and  coasts.  Another  genus 
of  Ganoids  (or  fish  with  hard,  shining,  and  enamelled  scales),  called 
jEchmodus  (see  fig.  411),  is  almost  exclusively  Liassic.  The  teeth  of  a 
species  of  Acrodus,  also,  are  very  abundant  in  the  lias  (fig.  412). 

6  a  Tig.  411. 


I.  Scales  of  JSchmodus 
Leachii. 


a.  jEchmodus     Ecstored  outline. 
Fig.  412. 


c.  Scales  of  Dape- 
dius  monUifer. 


Acrodvs  nobttis,  Agas.  (tooth) ;  commonly  called  fossil  leach. 
Lias,  Lyme  Kegis  and  Germany. 

But  the  remains  of  fish  which  have  excited  more  attention  than  any 
others,  are  those  large  bony  spines  called  iehthyodorulites  (a,  fig.  413), 
which  were  once  supposed  by  some  naturalists  to  be  jaws,  and  by  others 


Fig.  413. 


Hybodv*  reticulatug,  Agas.    Lias,  Lyme  Eegis. 

a.  Part  of  fin,  commonly  called  Ichthyodorulite. 
5.  Tooth. 

weapons,  resembling  those  of  the  living  Balistes  and  Silurus  •  but  which 
M.  Agassiz  has  shown  to  be  neither  the  one  nor  the  other.  The  spines, 
in  the  genera  last  mentioned,  articulate  with  the  backbone,  whereas  there 
are  no  signs  of  any  such  articulation  in  the  iehthyodorulites.  These  last 


*  Agassiz,  Pois.  Fos.  vol  :i.  tab.  28,  29. 
21 


322  REPTILES  OF  THE  LIAS.  [On.  XXL 

appear  to  have  been  bony  spines  which  formed  the  anterior  part  of  the 
dorsal  fin,  like  that  of  the  living  genera  Cestracion  and  Chimcera  (see  a, 
fig.  414).  In  both  of  these  genera,  the  posterior  concave  face  is  armed 


Fig.  414. 


Chimcera  monstrosa* 
a.  Spine  forming  anterior  part  of  the  dorsal  fin. 

with  small  spines,  as  in  that  of  the  fossil  Hybodus  (fig.  413),  one  of  the 
shark  family  found  fossil  at  Lyme  Regis.  Such  spines  are  simply  imbed- 
ded in  the  flesh,  and  attached  to  strong  muscles.  "  They  serve,"  says 
Dr.  Buckland,  "as  in  the  Chimcera  (fig.  414),  to  raise  and  depress  the 
fin,  their  action  resembling  that  of  a  movable  mast,  raising  and  lowering 
backwards  the  sail  of  a  barge. "f 

Reptiles  of  the  Lias. — It  is  not,  however,  the  fossil  fish  which  form 
the  most  striking  feature  in  the  organic  remains  of  the  Lias ;  but  the 
reptiles,  which  are  extraordinary  for  their  number,  size,  and  structure. 
Among  the  most  singular  of  these  are  several  species  of  Ichthyosaurus  and 
Plesiosaurus  (figs.  415,  416).  The  genus  Ichthyosaurus,  or  fish-lizard, 
is  not  confined  to  this  formation,  but  has  been  found  in  strata  as  high 
as  the  lower  chalk  of  England,  and  as  low  as  the  trias  of  Germany, 
a  formation  which  immediately  succeeds  the  lias  in  the  descending 
order.J  It  is  evident  from  their  fish-like  vertebra,  their  paddles,  re- 
sembling those  of  a  porpoise  or  whale,  the  length  of  their  tail,  and  other 
parts  of  their  structure,  that  the  habits  of  the  Ichthyosaurs  were  aquatic. 
Their  jaws  and  teeth  show  that  they  were  carnivorous ;  and  the  half- 
digested  remains  of  fishes  and  reptiles,  found  within  their  skeletons,  in- 
dicate the  precise  nature  of  their  food.§ 

A  specimen  of  the  hinder  fin  or  paddle  of  Ichthyosaurus  communis 
was  discovered  in  1840  at  Barrow-on-Soar,  by  Sir  P.  Egerton,  which 
distinctly  exhibits  on  its  posterior  margin  the  remains  of  cartilaginous 
rays  that  bifurcate  as  they  approach  the  edge,  like  those  in  the  fin  of  a 
fish  (see  a,  fig.  417).  It  had  previously  been  supposed,  says  Prof.  Owen, 
that  the  locomotive  organs  of  the  Ichthyosaurus  were  enveloped,  while 
living,  in  a  smooth  integument,  like  that  of  the  turtle  and  porpoise, 
which  has  no  other  support  than  is  afforded  by  the  bones  and  ligaments 
within ;  but  it  now  appears  that  the  fin  was  much  larger,  expanding  far 

*  Agassiz,  Poissons  Fossiles,  vol.  iii.  tab.  C.  fig.  1. 

f  Bridgewater  Treatise,  p.  290.  +  Ibid.  p.  168.  §  Ibid.  p.  187. 


CH.  XXI] 


LIAS — SAUKIANTS. 


323 


beyond  its  osseous  framework,  and  deviating  widely  in  its  fish-like  rays 
from  the  ordinary  reptilian  type.  In  fig.  417,  the  posterior  bones,  or 
digital  ossicles  of  the  paddle,  are  seen  near  b  ;  and  beyond  these  is  the 
dark  carbonized  integument  of  the  terminal  half  of  the  fin,  the  outline 
of  which  is  beautifully  defined.*  Prof.  Owen  believes  that,  besides  the 
fore-paddles,  these  short  and  stiff-necked  saurians  were  furnished  with  a 
tail-fin  without  radiating  bones,  and  purely  tegumentary,  expanding  in  a 
vertical  direction ;  an  organ  of  motion  which  enabled  them  to  turn 
their  heads  rapidly .f 


*  GeoL  Soc.  Transact  Second  Series,  vol.  vi.  p.  199,  pL  xx. 
f  Gcol.  Soc.  Transact.  Second  Series,  YoL  v.  p.  511. 


324  LIAS — SAURIANS.  [Cit  XXI. 

Fig.  417. 


Posterior  part  of  hind  fin  or  paddle  of  Ichthyosaurus  communis. 

Mr.  Conybeare  was  enabled,  in  1824,  after  examining  many  skeletons 
nearly  perfect,  to  give  an  ideal  restoration  of  the  osteology  of  this  genus, 
and  of  that  of  the  Plesiosaurus*  (See  figs.  415,  416.)  The  latter  an- 
imal had  an  extremely  long  neck  and  small  head,  with  teeth  like  those 
of  the  crocodile,  and  paddles  analogous  to  those  of  the  Ichthyosaurus, 
but  larger.  It  is  supposed  to  have  lived  in  shallow  seas  and  estuaries, 
and  to  have  breathed  air  like  the  Ichthyosaur,  and  our  modern  cetacea.f 
Some  of  the  reptiles  above  mentioned  were  of  formidable  dimensions. 
One  specimen  of  Ichthyosaurus  platyodon,  from  the  lias  at  Lyme,  now  in 
the  British  Museum,  must  have  belonged  to  an  animal  more  than  24 
feet  in  length ;  and  another  of  the  Plesiosaurus,  in  the  same  collection, 
is  11  feet  long.  The  form  of  the  Ichthyosaurus  may  have  fitted  it  to 
cut  through  the  waves  like  the  porpoise ;  but  it  is  supposed  that  the 
Plesiosaurus,  at  least  the  long-necked  species  (fig.  416),  was  better 
suited  to  fish  in  shallow  creeks  and  bays  defended  from  heavy  breakers. 

In  many  specimens  both  of  Ichthyosaur  and  Plesiosaur  the  bones  of  the 
head,  neck,  and  tail  are  in  their  natural  position,  while  those  of  the  rest 
of  the  skeleton  are  detached  and  in  confusion.  Mr.  Stutchburg  has 
suggested  that  their  bodies  after  death  became  inflated  with  gases,  and, 
while  the  abdominal  viscera  were  decomposing,  the  bones,  though  dis- 
united, were  retained  within  the  tough  dermal  covering  as  in  a  bag,  until 
the  whole,  becoming  water-logged,  sank  to  the  bottom.];  As  they  be- 
longed to  individuals  of  all  ages,  they  are  supposed,  by  Dr.  Buckland, 
to  have  experienced  a  violent  death ;  and  the  same  conclusion  might  also 
be  drawn  from  their  having  escaped  the  attacks  of  their  own  predacious 
race,  or  of  fishes,  found  fossil  in  the  same  beds. 

For  the  last  twenty  years,  anatomists  have  agreed  that  these  extinct 
saurians  must  have  inhabited  the  sea ;  and  it  was  urged  that,  as  there 
are  now  chelonians,  like  the  tortoise,  living  in  freshwater,  and  others, 

*  Geol.  Trans.  Second  Series,  vol.  i.  pi.  49. 

f  Conybeare  and  De  la  Beche,  Geol.  Trans.  1st  Ser.  vol.  v.  p.  559 ;  and  Buck- 
land,  Bridgw.  Treatise,  p.  203. 

J  Quarterly  Geol.  Journal,  vol.  ii.  p.  4 1 1. 


CH.  XXL]  LIAS — SAURIANS.  325 

as  the  turtle,  frequenting  the  ocean,  so  there  may  have  been  formerly 
some  saurians  proper  to  salt,  others  to  fresh  water.  The  common  croco- 
dile of  the  Ganges  is  well  known  to  frequent  equally  that  river  and  the 
brackish  and  salt  water  near  its  mouth ;  and  crocodiles  are  said  in  like 
manner  to  be  abundant  both  in  the  rivers  of  the  Isla  de  Pinos  (or  Isle  of 
Pines),  south  of  Cuba,  and  in  the  open  sea  round  the  coast.  More  re- 
cently a  saurian  has  been  discovered  of  aquatic  habits  and  exclusively 
marine.  This  creature  was  found  in  the  Galapagos  Islands,  during  the 
visit  of  H.  M.  S.  Beagle  to  that  archipelago,  in  1835,  and  its  habits 
were  then  observed  by  Mr.  Darwin.  The  islands  alluded  to  are  situated 
under  the  equator,  nearly  600  miles  to  vhe  westward  of  the  coast  of 
South  America.  They  are  volcanic,  some  of  them  being  3000  or  4000 
feet  high ;  and  one  of  them,  Albemarle  Island,  75  miles  long.  The 
climate  is  mild ;  very  little  rain  falls ;  and,  in  the  tfhole  archipelago, 
there  is  only  one  rill  of  fresh  water  that  reaches  the  coast  The  soil  is 
for  the  most  part  dry  and  harsh,  and  the  vegetation  scanty.  The  b'.rds, 
reptiles,  plants,  and  insects  are,  with  very  few  exceptions,  of  species 
found  nowhere  else  in  the  world,  although  all  partake,  in  their  general 
form,  of  a  South  American  type.  Of  the  mammalia,  says  Mr.  Darwin, 
one  species  alone  appears  to  be  indigenous,  namely,  a  large  and  peculiar 
kind  of  mouse ;  but  the  number  of  lizards,  tortoises,  and  snakes  is  so 
great,  that  it  may  be  called  a  land  of  reptiles.  The  variety,  indeed,  of 
species  is  small ;  but  the  individuals  of  each  are  in  wonderful  abundance. 
There  is  a  turtle,  a  large  tortoise  (Testudo  Indicus),  four  lizards,  and 
about  the  same  number  of  snakes,  but  no  frogs  or  toads.  Two  of  the 
lizards  belong  to  the  family  Iguanidoe  of  Bell,  and  to  a  peculiar  genus 
(Amblyrhynchus)  established  by  that  naturalist,  and  so  named  from 
their  obtusely  truncated  head  and  short  snout.*  Of  these  lizards  one 
is  terrestrial  in  its  habits,  and  burrows  in  the  ground,  swarming  every- 
where on  the  land,  having  a  round  tail,  and  a  mouth  somewhat  resem- 
bling in  form  that  of  the  tortoise.  The  other  is  aquatic,  and  has  its  tail 
flattened  laterally  for  swimming  (see  fig.  418.)  "This  marine  saurian," 

Fig.  418. 


AtnttyrTiyncTius  cristatw,  Bell.    Length  varying  from  3  to  4  feet    The  only  existing  marine 
lizard  now  known. 

a.  Tooth,  natural  size  and  magnified. 
amblys,  blunt ;  and  pvyxos,  rhynchus,  snout. 


326  SUDDEN  DESTRUCTION  OF  SAUEIANS.  [Cn.  XXI. 

says  Mr.  Darwin,  "  is  extremely  common  on  all  the  islands  throughout 
the  archipelago.  It  lives  exclusively  on  the  rocky  sea-beaches,  and  I 
never  saw  one  even  ten  yards  inshore.  The  usual  length  is  about  a 
yard,  but  there  are  some  even  4  feet  long.  It  is  of  a  dirty  black  color, 
sluggish  in  its  movements  on  the  land ;  but,  when  in  the  water,  it  swims 
with  perfect  ease  and  quickness  by  a  serpentine  movement  of  its  body 
and  flattened  tail,  the  legs  during  this  time  being  motionless,  and  closely 
collapsed  on  its  sides.  Their  limbs  and  strong  claws  are  admirably 
adapted  for  crawling  over  the  rugged  and  fissured  masses  of  lava  which 
everywhere  form  the  coast.  In  such  situations,  a  group  of  six  or  seven 
of  these  hideous  reptiles  may  oftentimes  be  seen  on  the  black  rocks,  a 
few  feet  above  the  surf,  basking  in  the  sun  with  outstretched  legs. 
Their  stomachs,  on  being  opened,  were  found  to  be  largely  distended 
with  minced  sea-weed,  of  a  kind  which  grows  at  the  bottom  of  the  sea 
at  some  little  distance  from  the  coast.  To  obtain  this,  the  lizards  go  out 
to  sea  in  shoals.  One  of  these  animals  was  sunk  in  salt-water,  from 
the  ship,  with  a  heavy  weight  attached  to  it,  and  on  being  drawn  up 
again  after  an  hour  it  was  quite  active  and  unharmed.  It  is  not  yet 
known  by  the  inhabitants  where  this  animal  lays  its  eggs ;  a  sin- 
gular fact,  considering  its  abundance,  and  that  the  natives  are  well 
acquainted  with  the  eggs  of  the  terrestrial  AmUyrhynchus,  which  is  also 
herbivorous."* 

In  those  deposits  now  forming  by  the  sediment  washed  away  from  the 
wasting  shores  of  the  Galapagos  Islands  the  remains  of  saurians,  both  of 
the  land  and  sea,  as  well  as  of  chelonians  and  fish,  may  be  mingled  with 
marine  shells,  without  any  bones  of  land  quadrupeds  or  batrachian  rep- 
tiles ;  yet  even  here  we  should  expect  the  remains  of  marine  mammalia 
to  be  imbedded  in  the  new  strata,  for  there  are  seals,  besides  several 
kinds  of  cetacea,  on  the  Galapagian  shores ;  and,  in  this  respect,  the 
parallel  between  the  modern  fauna,  above  described,  and  the  ancient  one 
of  the  lias,  would  not  hold  good. 

Sudden  destruction  of  saurians. — It  has  been  remarked,  and  truly, 
that  many  of  the  fish  and  saurians,  found  fossil  in  the  lias,  must  have 
met  with  sudden  death  and  immediate  burial ;  and  that  the  destructive 
operation,  whatever  may  have  been  its  nature,  was  often  repeated. 

"  Sometimes,"  says  Dr.  Buckland,  "  scarcely  a  single  bone  or  scale  has 
been  removed  from  the  place  it  occupied  during  life ;  which  could  not 
have  happened  had  the  uncovered  bodies  of  these  saurians  been  left, 
even  for  a  few  hours,  exposed  to  putrefaction,  and  to  the  attacks  of  fishes, 
and  other  smaller  animals  at  the  bottom  of  the  sea."f  Not  only  are  the 
skeletons  of  the  Ichthyosaurs  entire,  but  sometimes  the  contents  of  their 
stomachs  still  remain  between  their  ribs,  as  before  remarked,  so  that  we 
can  discover  the  particular  species  of  fish  on  which  they  lived,  and 
the  form  of  their  excrements.  Wot  unfrequently  there  are  layers  of 
these  coprolites,  at  different  depths  in  the  lias,  at  a  distance  from  any 

*  Darwin's  Journal,  chap.  xix.  f  Bridges.  Treat,  p.  125. 


CH.  XXL]  FOSSILS   OF  THE   LIAS.  327 

entire  skeletons  of  the  marine  lizards  from  which  they  were  derived  "  as 
ifj"  says  Sir  H.  De  la  Beche,  "  the  muddy  bottom  of  the  sea  received 
small  sudden  accessions  of  matter  from  time  to  time,  covering  up  the 
coprolites  and  other  exuviae  which  had  accumulated  during  the  inter- 
vals."* It  is  farther  stated  that,  at  Lyme  Regis,  those  surfaces  only  of 
the  coprolites  which  lay  uppermost  &t  the  bottom  of  the  sea  have  suf- 
fered partial  decay,  from  the  action  of  water  before  they  were  covered 
and  protected  by  the  muddy  sediment  that  has  afterwards  permanently 
enveloped  them.f 

Numerous  specimens  of  the  Calamary,  or  pen-and-ink  fish  (Geoteuthis 
Bollensis,  Schuble  sp.)  have  also  been  met  with  in  the  lias  at  Lyme,  with 
the  ink-bags  still  distended,  containing  the  ink  in  a  dried  state,  chiefly 
composed  of  carbon,  and  but  slightly  impregnated  with  carbcuate  of 
lime.  These  cephalopoda,  therefore,  must,  like  the  saurians,.have  been 
soon  buried  in  sediment ;  for,  if  long  exposed  after  death,  the  membrane 
containing  the  ink  would  have  decayed.^ 

As  we  know  that  river  fish  are  sometimes  stifled,  even  in  their  own 
element,  by  muddy  water  during  floods,  it  cannot  be  doubted  that  the 
periodical  discharge  of  large  bodies  of  turbid  fresh  water  into  the  sea 
may  be  still  more  fatal  to  marine  tribes.  In  the  Principles  of  Geology 
I  have  shown  that  large  quantities  of  mud  and  drowned  animals  have 
been  swept  down  into  the  sea  by  rivers  during  earthquakes,  as  in  Java, 
in  1699  ;  and  that  undescribable  multitudes  of  dead  fishes  have  been 
seen  floating  on  the  sea  after  a  discharge  of  noxious  vapors  during  simi- 
lar convulsions.§  But,  in  the  intervals  between  such  catastrophes,  strata 
may  have  accumulated  slowly  in  the  sea  of  the  lias,  some  being  formed 
chiefly  of  one  description  of  shell,  such  as  ammonites,  others  of  gryphites. 

From  the  above  remarks  the  reader  will  infer  that  the  lias  is  for  the 
most  part  a  marine  deposit.  Some  members,  however,  of  the  series, 
especially  in  the  lowest  part  of  it,  have  an  estuary  character,  and  must 
have  been  formed  within  the  influence  of  rivers.  In  Gloucestershire, 
where  there  is  a  good  type  of  the  lias  of  the  West  of  England,  it  has 
been  divided  into  an  upper  mass  of  shale  with  a  base  of  marlstone,  and  a 
lower  series  of  shales  with  underlying  limestones  and  shales.  We  learn 
from  the  researches  of  the  Rev.  P.  B.  Brodie,||  that  in  the  superior  of 
these  two  divisions  numerous  remains  of  insects  and  plants  have  been 
detected  in  several  places,  mingled  with  marine  shells  ;  but  in  the  infe- 
rior division  similar  fossils  are  still  more  plentiful.  One  band,  rarely 
exceeding  a  foot  in  thickness,  has  been  named  the  "  insect  limestone."  It 
passes  upwards  into  a  shale  containing  Cypris  and  Estheria,  and  is 
charged  with  the  wing-cases  of  several  genera  of  coleoptera,  anci  with 
some  nearly  entire  beetles,  of  which  the  eyes  are  preserved.  The  ner- 
vures  of  the  wings  of  neuropterous  insects  (fig.  419)  are  beautifully  per- 

*  Geological  Researches,  p.  334. 

f  Buckland,  Bridgew.  Treat,  p.  307.  t  Ibid. 

§  See  Principles,  Index,  Lancerote,  Graham  Island,  Calabria. 

||  A  history  of  Fossil  Insects,  <tc.  1846.     Londoa 


328  FOSSIL  PLANTS.  [Cn.  XXI. 

Fig.  410.  fect  in  this  bed.  Ferns,  with  leaves  of  mo 

nocotyledouous  plants,  and  some  apparently 
brackish  and  freshwater  shells,  accompany 
the  insects  in  several  places,  while  in  others 

Nat  size<  marine  shells  predominate,  the  fossils  varying 

Wing  of  a  nenropterous  insect,  from  -111 

the  Lower  Lias,  Gloucestershire,     apparently  as  we  examine  the  bed  nearer  or 
farther  from  the  ancient  land,  or  the  source 

whence  the  freshwater  was  derived.  There  are  two,  or  even  three,  bands 
of  "  insect  limestone"  in  several  sections,  and  they  have  been  ascertained 
by  Mr.  Brodie  to  retain  the  same  lithological  and  zoological  characters 
when  traced  from  the  centre  of  Warwickshire  to  the  borders  of  the 
southern  part  of  Wales.  After  studying  300  specimens  of  these  insects 
from  the  lias,  Mr.  Westwood  declares  that  they  comprise  both  wood- 
eating  and  herb-devouring  beetles  of  the  Linnean  genera  Elater,  Cara- 
bus,  &c.,  besides  grasshoppers  (Gryllus),  and  c.-etached  wings  of  dragon- 
flies  and  may-flies,  or  insects  referable  to  the  Linnean  genera  Libellula, 
Ephemera,  Hemerobius,  and  Panorpa,  in  all  belonging  to  no  less  than 
twenty-four  families.  The  size  of  the  species  is  usually  small,  and  such 
as  taken  alone  would  imply  a  temperate  climate ;  but  many  of  the  as- 
sociated organic  remains  of  other  classes  must  lead  to  a  different  conclu- 
sion. 

Fossil  plants. — Among  the  vegetable  remains  of  the  Lias,  several 
species  of  Zamia  have  been  found  at  Lyrne  Regis,  and  the  remains  of 
coniferous  plants  at  Whitby.  Fragments  of 
wood  are  common,  and  often  converted  into 
limestone.  That  some  of  this  wood,  though 
now  petrified,  was  soft  when  it  first  lay  at 
the  bottom  of  the  sea,  is  shown  by  a  speci- 
men now  in  the  museum  of  the  Geological 
Society  (see  fig.  420),  which  has  the  form 
of  an  ammonite  indented  on  its  surface. 

M.  Ad.  Brongniart  enumerates  forty-seven  liassic  acrogens,  most  of 
them  ferns  ;  and  fifty  gymnogens,  of  which  thirty-nine  are  cycads,  and 
eleven  conifers.  Among  the  cycads  the  predominance  of  Zamites  and 
Nilsonia,  and  among  the  ferns  the  numerous  genera  with  leaves  having 
reticulated  veins  (as  in  fig.  385,  p.  314),  are  mentioned  as  botanical 
characteristics  of  this  era.*  The  absence  as  yet  from  the  Lias  and  Oolite 
of  all  signs  of  dicotyledonous  angiosperms  is  worthy  of  notice.  The  leaves 
of  such  plants  are  frequent  in  tertiary  strata,  and  occur  in  the  Cretaceous, 
though  less  plentifully  (see  above,  p.  266).  The  angiosperms  seem,  there- 
fore, to  have  been  at  the  least  comparatively  rare  in  these  older  secondary 
periods,  when  more  space  was  occupied  by  the  Cycads  and  Conifers. 

Origin  of  the  Oolite  and  Lias. — If  we  now  endeavor  to  restore,  in 
imagination,  the  ancient  condition  of  the  European  area  at  the  period  of 
the  Oolite  and  Lias,  we  must  conceive  a  sea  in  which  the  growth  of 

*  Tableau  des  Veg.  Fos.  1849,  p.  105 


Ca   XXL]  OEIGIN  OF  THE   OOLITE  AND  LIAS.  329 

coral  reefs  and  shelly  limestones,  after  proceeding  without  interruption 
for  ages,  was  liable  to  be  stopped  suddenly  by  the  deposition  of  clayey 
sediment  Then,  again,  the  argillaceous  matter,  devoid  of  corals,  was 
deposited  for  ages,  and  attained  a  thickness  of  hundreds  of  feet,  until 
another  period  arrived  when  the  same  space  was  again  occupied  by  cal- 
careous sand,  or  solid  rocks  of  shell  and  coral,  to  be  again  succeeded  by 
the  recurrence  of  another  period  of  argillaceous  deposition.  Mr.  Cony- 
beare  has  remarked  of  the  entire  group  of  Oolite  and  Lias,  that  it  consists 
of  repeated  alternations  of  clay,  sandstone,  and  limestone,  following  each 
other  in  the  same  order.  Thus  the  clays  of  the  lias  are  followed  by  the 
sands  of  the  inferior  oolite,  and  these  again  by  shelly  and  coralline  lime- 
stone (Bath  oolite,  &c.)  ;  so,  in  the  middle  oolite,  the  Oxford  clay  is  fol- 
lowed by  calcareous  grit  and  "  coral  rag ;"  lastly,  in  the  upper  oolite,  the 
Kimmeridge  clay  is  followed  by  the  Portland  sand  and  limestone.*  The 
clay  beds,  however,  as  Sir  H.  De  la  Beche  remarks,  can  be  followed 
over  larger  areas  than  the  sands  or  sandstones.^  It  should  also  be  re- 
membered that  while  the  oolitic  system  becomes  arenaceous,  and  resem- 
bles a  coal-field  in  Yorkshire,  it  assumes,  in  the  Alps,  an  almost  purely 
calcareous  form,  the  sands  and  clays  being  omitted ;  and  even  in  the 
intervening  tracts,  it  is  more  complicated  and  variable  than  appears  in 
ordinary  descriptions.  Nevertheless,  some  of  the  clays  and  intervening 
limestones  do,  in  reality,  retain  a  pretty  uniform  character,  for  distances 
of  from  400  to  600  miles  from  east  to  west  and  north  to  south. 

According  to  M.  Thirria,  the  entire  oolitic  group  in  the  department  of 
the  Haute  Saone,  in  France,  may  be  equal  in  thickness  to  that  of  Eng- 
land ;  but  the  importance  of  the  argillaceous  divisions  is  in  the  inverse 
ratio  to  that  which  they  exhibit  in  England,  where  they  are  about  equal 
to  twice  the  thickness  of  the  limestones,  whereas,  in  the  part  of  France 
alluded  to,  they  reach  only  about  a  third  of  that  thickness.J;  In  the 
Jura  the  clays  are  still  thinner ;  and  in  the  Alps  they  thin  out  and 
almost  vanish. 

In  order  to  account  for  such  a  succession  of  events,  we  may  imagine, 
first,  the  bed  of  the  ocean  to  be  the  receptacle  for  ages  of  fine  argilla- 
ceous sediment,  brought  by  oceanic  currents,  which  may  have  communi- 
cated with  rivers,  or  with  part  of  the  sea  near  a  wasting  coast.  This 
mud  ceases,  at  length,  to  be  conveyed  to  the  same  region,  either  because 
the  land  which  had  previously  suffered  denudation  is  depressed  and  sub- 
merged, or  because  the  current  is  deflected  in  another  direction  by  the 
altered  shape  of  the  bed  of  the  ocean  and  neighboring  dry  land.  By 
such  changes  the  water  becomes  once  more  clear  and  fit  for  the  growth 
of  stony  zoophytes.  Calcareous  sand  is  then  formed  from  comminuted 
shell  and  coral,  or,  in  some  cases,  arenaceous  matter  replaces  the  clay ; 
because  it  commonly  happens  that  the  finer  sediment,  being  first  drifted 
farthest  from  coasts,  is  subsequently  overspread  by  coarse  sand,  after  the 

*  Con.  and  Phil.  p.  166.  f  Geol.  Researches,  p.  387. 

\  Burat's  D'Aubuisson,  torn.  ii.  p.  456. 


330  OOLITE  AND  LIAS  [Cn.  XXI 

sea  lias  grown  shallower,  or  when  the  land,  increasing  in  extent,  whether 
by  upheaval  or  by  sediment  filling  up  parts  of  the  sea,  has  approached 
nearer  to  the  spots  first  occupied  by  fine  mud. 

In  order  to  account  for  another  great  formation,  like  the  Oxford  clay, 
again  covering  one  of  coral  limestone,  we  must  suppose  a  sinking  down 
like  that  which  is  now  taking  place  in  some  existing  regions  of  coral 
between  Australia  and  South  America.  The  occurrence  of  subsidences, 
on  so  vast  a  scale,  may  have  caused  the  bed  of  the  ocean  and  the  adjoin- 
ing land,  throughout  great  parts  of  the  European  area,  to  assume  a 
shape  favorable  to  the  deposition  of  another  set  of  clayey  strata ;  and 
this  change  may  have  been  succeeded  by  a  series  of  events  analogous  to 
that  already  explained,  and  these  again  by  a  third  series  in  similar  order. 
Both  the  ascending  and  descending  movements  may  have  been  extremely 
slow,  like  those  now  going  on  in  the  Pacific  ;  and  the  growth  of  every 
stratum  of  coral,  a  few  feet  of  thickness,  may  have  required  centuries 
for  its  completion,  during  which  certain  species  of  organic  beings  disap- 
peared from  the  earth,  and  others  were  introduced  in  their  place ;  so  that, 
in  each  set  of  strata,  from  the  Lias  to  the  Upper  Oolite,  some  peculiar 
and  characteristic  fossils  were  imbedded. 

Oolite  and  Lias  of  the  United  States. 

There  are  large  tracts  on  the  globe,  as  in  Russia  and  the  United  States, 
where  all  the  members  of  the  oolitic  series  are  unrepresented.  In  the 
state  of  Virginia,  however,  at  the  distance  of  about  13  miles  eastward 
of  Richmond,  the  capital  of  that  state,  there  is  a  regular  coal-field  oc- 
curring in  a  depression  of  the  granite  rocks  (see  section,  fig.  421),  which 


Section  showing  the  geological  position  of  the  James  Eiver,  or  East  Virginian  Coal-field. 

A.  Granite,  gneiss,  &c.  B.  Coal-measures. 

C.  Tertiary  strata.  D.  Drift  or  ancient  alliwium. 

Professor  W.  B.  Rogers  first  correctly  referred  to  the  age  of  the  lower 
part  of  the  Jurassic  group.  This  opinion  I  was  enabled  to  confirm  after 
collecting  a  large  number  of  fossil  plants,  fish,  and  shells,  and  examining 
the  coal-field  throughout  its  whole  area.  It  extends  26  miles  from  north 
to  south,  and  from  4  to  12,  from  east  to  west.  The  plants  consist  chiefly 
of  zamites,  calamites,  and  equisetums,  and  these  last  are  very  commonly 
met  with  in  a  vertical  position  more  or  less  compressed  perpendicularly. 
It  is  .clear  that  they  grew  in  the  places  where  they  are  now  buried  in 
strata  of  hardened  sand  and  mud.  I  found  them  maintaining  their  erect 
attitude,  at  points  many  miles  distant  from  others,  in  beds  both  above 


CH.  XXI]  OF  THE    UXITED   STATES.  331 

and  between  the  seams  of  coal.  In  order  to  explain  this  fact  we  must 
suppose  such  shales  and  sandstones  to  have  been  gradually  accumulated 
during  the  slow  and  repeated  subsidence  of  the  whole  region. 

It  is  worthy  of  remark  that  the  Equisetum  columnare  of  these  Virginian 
rocks  appears  to  be  undistinguishable  from  the  species  found  in  the  oolitic 
sandstones  near  Whitby  in  Yorkshire,  where  it  also  is  met  with  in  an  up- 
light  position.  One  of  the  Virginian  fossil  ferns,  Pecopteris  Whitbyensis, 
is  also  a  species  common  to  the  Yorkshire  oolites.*  These  Virginian  coal- 
measures  are  composed  of  grits,  sandstones,  and  shales,  exactly  resembling 
those  of  older  or  primary  date  in  America  and  Europe,  and  they  rival  or 
even  surpass  the  latter  in  the  richness  and  thickness  of  the  coal-seams. 
One  of  these,  the  main  seam,  is  in  some  places  from  30  to  40  feet  thick, 
composed  of  pure  bituminous  coal.  On  descending  a  shaft  800  feet  deep, 
in  the  Blackheath  mines  in  Chesterfield  county,  I  found  myself  in  a  cham- 
ber more  than  40  feet  high,  caused  by  the  removal  of  this  coal.  Timber 
props  of  great  strength  supported  the  roof,  but  they  were  seen  to  bend 
under  the  incumbent  weight.  The  coal  is  like  the  finest  kinds  shipped  at 
Newcastle,  and  when  analyzed  yields  the  same  proportions  of  carbon  and 
hydrogen,  a  fact  worthy  of  notice  when  we  consider  that  this  fuel  has  been 
derived  from  an  assemblage  of  plants  very  distinct  specifically,  and  in  part 
generically,  from  those  which  have  contributed  to  the  formation  of  the 
ancient  or  paleozoic  coal. 

The  fossil  fish  of  these  Richmond  strata  belong  to  the  liassic  genus  Tetra- 
gonolepis  (^Echmodus),  see  fig.  411,  and  to  a  new  genus  which  I  have 
called  Dictyopyge.  Shells  are  very  rare,  as  usually  in  all  coal-bearing  de- 
posits, but  a  species  of  Posidonomya  is  in  such  profusion  in  some  shaly 
beds  as  to  divide  them  like  the  plates  of  mica  in  micaceous  shales 
(see  fig.  422). 

Fig.  422. 


a.  Posidonomyd)  or  Estheria  ft    "  &.  Toang  of  same. 

Oolitic  coal-shale,  Eichmond,  Virginia. 

In  India,  especially  in  Cutch,  a  formation  occurs  clearly  referable  to  the 
oolitic  and  liassic  type,  as  shown  by  the  shells,  corals,  and  plants ;  and 
there  also  coal  has  been  procured  from  one  member  of  the  group. 

*  See  description  of  the  coal-field  by  the  author,  and  of  the  plants  by  C.  J.  F. 
Bunbury,  Esq.,  Quart  GeoL  Journ.  voL  iii.  p.  281. 

f  Possibly,  as  suggested  by  Prof.  Morris  (Geol.  Journ.  vol.  iii.  p.  2*75),  these 
delicate  bivalves  may  prove  to  belong  to  the  crustacean  genus  Estheria. 


NEW  RED  SANDSTONE. 


[Cn.  XXII. 


CHAPTER  XXIL 


TRIAS    OR    NEW    RED    SANDSTONE    GROUP. 

Distinction  between  New  and  Old  Red  Sandstone — Between  Upper  and  Lower 
New  Red — The  Trias  and  its  three  divisions — Most  largely  developed  in  Ger- 
many— Keuper  and  its  fossils — Muschelkalk  and  fossils — Fossil  plants  of  the 
Bunter — Triassic  group  in  England — Bone  bed  of  Axmouth  and  Aust — Red 
Sandstone  of  "Warwickshire  and  Cheshire — Footsteps  of  Chcirotherium  in  Eng- 
land and  Germany — Osteology  of  the  Lnbyrinthodon — Identification  of  this 
Batrachian  with  the  Cheirotherium — Triassic  mammifer — Origin  of  Red  Sand- 
stone and  Rock-salt — Hypothesis  of  saline  volcanic  exhalations — Theory  of  the 
precipitation  of  salt  from  inland  lakes  or  lagoons — Saltness  of  the  Red  Sea — 
New  Red  Sandstone  in  the  United  States — Fossil  footprints  of  birds  and  rep- 
tiles in  the  Valley  of  the  Connecticut — Antiquity  of  the  Red  Sandstone  con- 
taining them. 

BETWEEN  the  Lias  and  the  Coal,  or  Carboniferous  group,  there  is  in- 
terposed, in  the  midland  and  western  counties  of  England,  a  great  series 
of  red  loams,  shales,  and  sandstones,  to  which  the  name  of  the  New 
Red  Sandstone  formation  was  first  given,  to  distinguish  it  from  other 
shales  and  sandstones  called  the  "  Old  Red"  (c,  fig.  423),  often  identical 
in  mineral  character,  which  lie  immediately  beneath  the  coal  (6). 


Fig.  423. 


a.  New  red  sandstone. 


&.  Coal. 


c.  Old  red. 


The  name  of  "  Red  Marl"  has  been  incorrectly  applied  to  the  red  clays 
of  this  formation,  as  before  explained  (p.  13),  for  they  are  remarkably 
free  from  calcareous  matter.  The  absence,  indeed,  of  carbonate  of  lime, 
as  well  as  the  scarcity  of  organic  remains,  together  with  the  bright  red 
color  of  most  of  the  rocks  of  this  group,  causes  a  strong  contrast  between 
it  and  the  Jurassic  formations  before  described. 

Before  the  distinctness  of  the  fossil  remains  characterizing  the  upper 
and  lower  part  of  the  English  New  Red  had  been  clearly  recognized,  it 
was  found  convenient  to  have  a  common  name  for  all  the  strata  inter- 
mediate in  position  between  the  Lias  and  Coal ;  and  the  term  "  Poi- 
kilitic"  was  proposed  by  Messrs.  Conybeare  and  Buckland,*  from  rfojxiXos, 
variegated,  some  of  the  most  characteristic  strata  of  this  group  having 
been  called  variegated  by  Werner,  from  their  exhibiting  spots  and  streaks 
of  light  blue,  green,  and  buff  color,  in  a  red  base. 

*  Buckland,  Bridg.  Treat,  vol.  ii.  p.  83. 


CH.  XXIL1       KEUPER  AND   MUSCHELKALK  FORMATIONS. 


333 


A  single  term,  thus  comprehending  both  Upper  and  Lower  New  Red, 
or  the  Triassic  and  Permian  groups  of  modern  classifications,  may  still 
be  useful  in  describing  districts  where  we  have  to  speak  of  masses  of  red 
sandstone  and  shale,  referable,  in  part,  to  both  these  eras,  but  which,  in 
the  absence  of  fossils,  it  is  impossible  to  divide. 

Trias  or  Upper  New  Red  Sandstone  Group. 

The  accompanying  table  will  explain  the  subdivisions  generally  adopted 
for  the  uppermost  of  the  two  systems  above  alluded  to,  and  the  names 
given  to  them  in  England  and  on  the  Continent. 

Synonyms. 


Trias  or  Upper 
New  Red 
Sandstone  - 


German.  French, 

a.  Saliferous  and   gyp- ) 

seous    shales    and  >•  Keuper  -        -    Marnes  Irishes, 
sandstone      •        • } 

6.  (wanting  in  England) 

c.  Sandstone  and  quart-  )  Bunter-sand-    \  r  .    ^V^A 
zose  conglomerate    \     stein  -        -  \  Gr6s  blgarre" 


Fig.  424. 


I  shall  first  describe  this  group  as  it  occurs  in  Southwestern  and 
Northwestern  Germany,  for  it  is  far  more  fully  developed  there  than 
in  England  or  France.  It  has  been  called  the  Trias  by  German  writers, 
or  the  Triple  Group,  because  it  is  separable  into  three  distinct  formations, 
called  the  "Keuper,"  the  " Muschelkalk,"  and  the  "  Bunter-sandstein." 

The  Keuper,  the  first  or  newest  of  these,  is  1000  feet  thick  in  Wiir- 
temberg,  and  is  divided  by  Alberti  into  sandstone,  gypsum,  and  carbona- 
ceous slate-clay.*  Remains  of  Reptiles, 
called  Nothosaurus  and  Phytosaurus,  have 
been  found  in  it  with  Labyrinthodon ;  the 
detached  teeth,  also,  of  placoid  fish  and  of 
rays,  and  of  the  genera  Sauricthys  and  Gy- 
rolepis  (figs.  433,  434,  p.  336).  The  plants 
of  the  Keuper  are  generically  very  analogous 
to  those  of  the  lias  and  oolite,  consisting  oi 
ferns,  equisetaceous  plants,  cycads,  and  coni- 
fers, with  a  few  doubtful  monocotyledons.  A 
few  species,  such  as  Equisetites  columnaris, 
are  common  to  this  group,  and  the  oolite. 
The  Muschelkalk  consists  chiefly  of  a  compact,  grayish  limestone,  but 
includes  beds  of  dolomite  in  many  places,  together  with  gypsum  and 
rock-salt.  This  limestone,  a  rock  wholly  unrepresented  in  England, 
abounds  in  fossil  shells,  as  the  name  implies.  Among  the  cephalopoda 
there  are  no  belemnites,  and  no  ammonites  with  foliated  sutures,  as  in 
the  incumbent  lias  and  oolite,  but  a  genus  allied  to  the  Ammonite,  called 
Ceratites'bj DeHaan,  in  which  the  descending  lobes  (see  a,  6,  c,  fig.  425) 
terminate  in  a  few  small  denticulations  pointing  inwards.  Among  the 

*  Monog.  des  Bunten  Sandsteins. 


Equisetites   columnaris, 
Equisetum  columnare.) 
ment  of  stem,  and  small  portion 
of  same  magnified.    Keuper. 


334 


THE  BUNTER-SANDSTEIN. 
a  Fig.  425.  & 


[On.  XXII. 


Ceratites  nodosus.    Muschelkalk. 

a.  Side  view.  &.  Front  view, 

c.  Partially  denticulated  outline  of  the  septa  dividing  the  chambers. 

bivalve  shells,  the  Posidonia  minuta,  Goldf.  (Posidonomya  minuta, 
Bronn)  (see  fig.  426),  is  abundant,  ranging  through  theKeuper,  Muschel- 
kalk, and  Bunter-sandstein ;  and  Avicula  socialis,  fig.  427,  having  a 
similar  range,  is  very  characteristic  of  the  Muschelkalk  in  Germany, 
France,  and  Poland. 

Fig.  426.  Fig.  427. 


Posidonia  minuta,  a.  Aviciila  socialis.  &.  Side  view  of  same. 

Goldf.    (Posido-  Characteristic  of  the  Muschelkalk. 

nomya  minuta, 
Bronn.) 

The  abundance  of  the  heads  and.  stems  of  lily  encrinites,  JEncrinus 
Fig.42S.  liliiformis,  fig.  428  (or  Encrinites  moniliformis),  show 

the  slow  manner  in  which  some  beds  of  this  limestone 
have  been  formed  in  clear  sea-water.  The  star-fish 
called  Aspidum  loricata  (fig.  429)  is  as  yet  peculiar 

Fig.  429. 


Encrinus  liliiformis,  Schlott.    Syn.  K  monttiformis. 

Body,  arms,  and  part  of  stem. 

a.  Section  of  stem. 

Muschelkalk. 


Aspidura  loricata,  Agas. 
a.  Upper  side. 
&.  Lower  side. 
Muschelkalk. 


CIL  XXIL]  THE   BUNTER-SANDSTEIN.  335 

to  the  Musclielkalk.     In  the  same  formation  are  found  ganoid  fish  with 
heterocercal  tails,  of  the  genus  Placodus.     (See  fig.  430.) 

Fig.  430.  Fig.  431. 


a.  Yolteia  heterophyUa.  (Syn.  Vottsia 

brevifolia.) 
&.  Portion  of  same  magnified  to  show 


>    fit/  '^*&*f*'f/  fructification.    Sulzbai 


Bunter-sandstein. 


Palatal  teeth  of  Plncodus  gigas. 
Muschelkalk. 


The  Bunter-sandstein  consists  of  various  colored  sandstones,  dolomites, 
and  red-clays,  with  some  beds,  especially  in  the  Hartz,  of  calcareous  piso- 
lite or  roe-stone,  the  whole  sometimes  attaining  a  thickness  of  more  than 
1000  feet.  The  sandstone  of  the  Vosges,  according  to  Von  Meyer,  is 
proved,  by  the  presence  of  Ldbyrinthodon,  to  belong  to  this  lowest  mem- 
ber of  the  Triassic  group.  At  Sulzbad  (or  Soultz-les-bains),  near  Stras- 
burg,  on  the  flanks  of  the  Vosges,  many  plants  have  been  obtained  from 
the  "  bunter,"  especially  conifers  of  the  extinct  genus  Voltzia,  peculiar  to 
this  period,  in  which  even  the  fructification  has  been  preserved.  (See 
fig.  431.) 

Out  of  thirty  species  of  ferns,  cycads,  conifers,  and  other  plants,  enu- 
merated by  M.  Ad.  Brongniart,  in  1849,  as  coming  from  the  "gres 
bigarre,"  or  Bunter,  not  one  is  common  to  the  Keuper.*  This  difference, 
however,  may  arise  partly  from  the  fact  that  the  flora  of  "  the  Bunter" 
has  been  almost  entirely  derived  from  one  district  (the  neighborhood  of 
Strasburg),  and  its  peculiarities  may  be  local. 

The  footprints  of  a  reptile  (Labyrinthodori)  have  been  observed  on  the 
clays  of  this  member  of  the  Trias,  near  Hildburghausen,  in  Saxony,  im- 
pressed on  the  upper  surface  of  the  beds,  and  standing  out  as  casts  in 
relief  from  the  under  sides  of  incumbent  slabs  of  sandstone.  To  these  I 
shall  again  allude  in  the  sequel ;  they  attest,  as  well  as  the  accompanying 
ripple-marks,  and  the  cracks  which  traverse  the  clays,  the  gradual  deposi- 
tion of  the  beds  of  this  formation  in  shallow  water,  and  sometimes  between 
high  and  low  water. 

Triassic  Group  in  England. 

In  England  the  Lias  is  succeeded  by  conformable  strata  of  red  and 
green  marl,  or  clay.  There  intervenes,  however,  both  in  the  neighbor- 
hood of  Axmouth,  in  Devonshire,  and  in  the  cliffs  of  Westbury  and 

*  Tableau  des  Genres  de  Veg.  Foa.,  Diet.  Univ.  1849. 


336 


TRIASSIC   GROUP  IN  ENGLAND. 


[On.  XXII. 


Aust,  in  Gloucestershire,  on  the  banks  of  the  Severn,  a  dark-colored 
stratum,  well  known  by  the  name  of  the  "  bone-bed."  It  abounds  in  the 
remains  of  saurians  and  fish,  and  was  formerly  classed  as  the  lowest  bed 
of  the  Lias ;  but  Sir  P.  Egerton  has  shown  that  it  should  be  referred  to 
the  Upper  New  Red  Sandstone,  for  it  contains  an  assemblage  of  fossil  fish 
which  are  either  peculiar  to  this  stratum  or  belong  to  species  well  known 
in  the  Muschelkalk  of  Germany.  These  fish  belong  to  the  genera  Acro- 
dus,  Hybodus,  Gyrolepis,  and  Saurichthys. 

Among  those  common  to  the  English  bone-bed  and  the  Muschelkalk 
of  Germany  are  Hybodus  plicatilis  (fig.  432),  Saurichthys  apicalis 
(fig.  433),  Gyrolepis  tennis triatus  (fig.  434),  and  G.  Albertii.  Remains 
of  saurians  have  also  been  found  in  the  bone-bed,  and  plates  of  an 
Encrinus. 


Fig.  433. 


Fig.  434. 


Fig.  432. 


Hybodus  plicatilis.    Teeth.    Bono-bed. 
Aust  and  Axmouth. 


Saurichthys  apicalis. 
Tooth :  nat.  size,  and 
magnified.  Axmouth. 


Gyrolepis  tenuistriatus. 
Scale ;  nat.  size,  and 
magnified.    Axmouth. 


The  strata  of  red  and  green  marl,  which  follow  the  bone-bed  in  the 
descending  order  at  Axmouth  and  Aust,  are  destitute  of  organic  remains ; 
as  is  the  case,  for  the  most  part,  in  the  corresponding  beds  in  almost 
every  part  of  England.  But  fossils  have  been  found  at  a  few  localities  in 
sandstones  of  this  formation,  in  Worcestershire  and  Warwickshire,  and 
among  them  the  bivalve  shell  called  Posidonia  minuta.  Goldf.,  before 
mentioned  (fig.  426,  p.  334). 

The  upper  member  of  the  English  "  New  Red"  containing  this  shell, 
in  those  parts  of  England,  is,  according  to  Messrs.  Murchison  and 
Strickland,  600  feet  thick,  and  consists  chiefly  of  red  marl  or  slate,  with 
a  band  of  sandstone.  Ichthyodorulites,  or  spines  of  Hybodus,  teeth  of 
fishes,  and  footprints  of  reptiles  were  observed  by  the  same  geologists 
in  these  strata  ;*  and  the  remains  of  a  saurian,  called  Rhynchosaurus, 
have  been  found  in  this  portion  of  the  Trias  at  Grinsell,  near  Shrews- 
bury. 

In  Cheshire  and  Lancashire  the  gypseous  and  saliferous  red  shales 
and  clays  of  the  Trias  are  between  1000  and  1500  feet  thick.  In  some 
places  lenticular  masses  of  rock-salt  are  interpolated  between  the  argilla- 
ceous beds,  the  origin  of  which  will  be  spoken  of  in  the  sequel. 

The  lower  division  or  English  representative  of  the  "  Bunter"  attains 


*  Geol.  Trans.,  Sec.  Ser.,  vol.  v.  p.  318,  <fec. 


Fig.  435. 


CH.  XXIL]     FOSSIL   FOOTSTEPS  IX  NEW  RED  SANDSTONE.          337 

a  thickness  of  600  feet  in  the  counties  last  mentioned.  Besides  red  and 
green  shales  and  red  sandstones,  it  comprises  much  soft  white  quartzose 
sandstone,  in  which  the  trunks  of  silicified  trees  have  been  met  with  at 
Allesley  Hill,  near  Coventry.  Several  of  them  were  a  foot  and  a  half  in 
diameter,  and  some  yards  in  length,  decidedly  of  coniferous  wood,  and 
showing  rings  of  annual  growth.*  Impressions,  also,  of  the  footsteps  of 
animals  have  been  detected  in  Lancashire  and  Cheshire  in  this  formation. 
Some  of  the  most  remarkable  occur  a  few  miles  from  Liverpool,  in  the 
whitish  quartzose  sandstone  of  Storton  Hill,  on  the  west  side  of  the  Mersey. 
They  bear  a  close  resemblance  to  tracks  first  observed  in  a  member  of  the 
Upper  New  Red  Sandstone,  at  the  village  of  Hesseberg,  near  Hildburg- 
hausen,  in  Saxony,  to  which  I  have  already  al- 
luded. For  many  years  these  footprints  have 
been  referred  to  a  large  unknown  quadruped, 
provisionally  named  Cheirotherium  by  Professor 
Kaup,  because  the  marks  both  of  the  fore  and 
hind  feet  resembled  impressions  made  by  a  hu- 
man hand.  (See  fig.  435.)  The  footmarks  at 
Hesseberg  are  partly  concave  and  partly  in  re- 
lief; the  former,  or  the  depressions,  are  seen 
upon  the  upper  surface  of  the  sandstone  slabs, 
but  those  in  relief  are  only  upon  the  lower  sur- 
faces, being  in  fact  natural  casts,  formed  in  the 
subjacent  footprints  as  in  moulds.  The  larger 
impressions,  which  seem  to  be  those  of  the  hind  foot,  are  generally  8 
inches  in  length,  and  5  in  width,  and  one  was  12  inches  long.  Near 
each  large  footstep,  and  at  a  regular  distance  (about  an  inch  and  a  half), 

Fig.  436. 


Single  footstep  of  Cheirothe- 
rium.  Banter  Sandstein, 
Saxony ;  one-eighth  of  nat. 
size. 


Line  of  footsteps  on  slab  of  sandstone.    Hildburghausen,  in  Saxony. 

before  it,  a  smaller  print  of  a  fore  foot,  4  inches  long  and  3.  inches  wide, 
occurs.  The  footsteps  follow  each  other  in  pairs,  each  pair  in  the  same 
line,  at  intervals  of  14  inches  from  pair  to  pair.  The  large  as  well  as  the 
small  steps  show  the  great  toes  alternately  on  the  right  and  left  side ; 
each  step  makes  the  print  of  five  toes,  the  first  or  great  toe  being  bent 
inwards  like  a  thumb.  .  Though  the  fore  and  hind  foot  differ  so  much  in 
size,  they  are  nearly  similar  in  form. 

The  similar  footmarks  afterwards  observed  in  a  rock  of  corresponding  age 
at  Storton  Hill,  were  imprinted  on  five  thin  beds  of  clay,  superimposed  one 
upon  the  other  in  the  same  quarry,  and  separated  by  beds  of  sandstone. 
On  the  lower  surface  of  the  sandstone  strata,  the  solid  casts  of  each  impres- 

*  Buckland,  Proc.  Geol.  Soc.  voL  ii.  p.  439 ;  and  Murchison  and  Strickland. 
Geol.  Trans.  Second  Ser.  vol.  v.  p.  347. 

22 


338  FOSSIL  KEMAINS  OF  LABYRINTHODON.        [On.  XXII 

sion  are  salient,  in  high  relief,  and  afford  models  of  the  feet,  toes,  and  claws 
of  the  animals  which  trod  on  the  clay.  On  the  same  surfaces  Mr.  J.  Cun- 
ningham discovered  (1839)  distinct  casts  of  rain-drop  markings. 

As  neither  in  Germany  nor  in  England  any  bones  or  teeth  had  been 
met  with  in  the  same  identical  strata  as  the  footsteps,  anatomists  indulged, 
for  several  years,  in  various  conjectures  respecting  the  mysterious  animals 
from  which  they  might  have  been  derived.  Professor  Kaup  suggested 
that  the  unknown  quadruped  might  have  been  allied  to  the  Marsupialia  ; 
for  in  the  kangaroo  the  first  toe  of  the  fore  foot  is  in  a  similar  manner  set 
obliquely  to  the  others,  like  a  thumb,  and  the  disproportion  between  the 
fore  and  hind  feet  is  also  very  great.  But  M.  Link  conceived  that  some 
of  the  four  species  of  animals  of  which  the  tracks  had  been  found  in 
Saxony  might  have  been  gigantic  Batrachians  ;  and  Dr.  Buckland  desig- 
nated some  of  the  footsteps  as  those  of  a  small  web-footed  animal,  prob- 
ably crocodilean. 

In  the  course  of  these  discussions  several  naturalists  of  Liverpool,  in 
their  report  on  the  Storton  quarries,  declared  their  opinion  that  each  of 
the  thin  seams  of  clay  in  which  the  sandstone  casts  were  moulded  had 
formed  successively  a  surface  above  water,  over  which  the  Ckeirotherium 
and  other  animals  walked,  leaving  impressions  of  their  footsteps,  and  that 
each  layer  had  been  afterwards  submerged  by  a  sinking  down  of  the  sur- 
face, so  that  a  new  beach  was  formed  at  low  water  above  the  former,  on 
which  other  tracks  were  then  made.  The  repeated  occurrence  of  ripple- 
marks  at  various  heights  and  depths  in  the  red  sandstone  of  Cheshire  had 
been  explained  in  the  same  manner.  It  was  also  remarked  that  impres- 
sions of  such  depth  and  clearness  could  only  have  been  made  by  animals 
walking  on  the  land,  as  their  weight  would  have  been  insufficient  to  make 
them  sink  so  deeply  in  yielding  clay  under  water.  They  must  therefore 
have  been  air-breathers. 

When  the  inquiry  had  been  brought  to  this  point,  the  reptilian  remains 
discovered  in  the  Trias,  both  of  Germany  and  England,  were  carefully 
examined  by  Prof.  Owen.  He  found,  after  a  microscopic  investigation  of 
the  teeth  from  the  German  sandstone  called  Keuper,  and  from  the  sand- 
stone of  Warwick  and  Leamington  (fig.  437),  that  neither  of  them  could 
be  referred  to  true  saurians,  although  they  had  been  named  Masto- 
donsaurus  and  Phytosaurus  by  Jager.  It  appeared  that  they  were -of 
the  Batrachian  order,  and  attested  the  former  ex- 
istence of  frogs  of  gigantic  dimensions  in  compari-  Fi£- 437- 
son  with  any  now  living.  Both  the  Continental 
and  English  fossil  teeth  exhibited  a  most  compli- 
cated texture,  differing  from  that  previously  ob- 
served in  any  reptile,  whether  recent  or  extinct,  but 

i  i  ,       ,1        7-7j7  Tooth  of  LabyrintJwdon ; 

most  nearly  analogous  to  the  Ichthyosaurus.     A       nat.  size.  Warwick  sand- 
section  of  one  of  these  teeth  exhibits  a  series  of       6tone' 
irregular  folds  resembling  the  labyrinthic  windings  of  the  surface  of 
the  brain ;  and  from  this  character  Prof.  Owen  has  proposed  the  name 
Labyrinthodon  for  the  new  genus.     The  annexed  representation  (fig. 


CH.  XXII.]  FOSSIL  REMAINS   OF   LABYRINTHODON. 


339 


438)  of  part  of  one  is  given  from  his  "  Odontography,"  plate  64,  A. 
The  entire  length  of  this  tooth  is  supposed  to  have  been  about  three 
inches  and  a  half,  and  the  breadth  at  the  base  one  inch  and  a  half. 


Fig.433. 


Transverse  section  of  tooth  of  Labyrinthodon  Jaegeri,  Owen  (Mastodonsaurus  Jaegerl^ 

Meyer) ;  nat  size,  and  a  segment  magnified. 
a.  Palp  cavity,  from  which  the  processes  of  pulp  and  dentine  radiate. 

When  Prof.  Owen  had  satisfied  himself,  from  an  inspection  of  the  cra- 
nium, jaws,  and  teeth,  that  a  gigantic  Batrachian  had  existed  at  the 
period  of  the  Trias  or  Upper  New  Red  Sandstone,  he  soon  found,  from 
the  examination  of  various  bones  derived  from  the  same  formation,  that 
he  could  define  three  species  of  Labyrinthodon,  and  that  in  this  genus 
the  hind  extremities  were  much  larger  than  the  anterior  ones.  This 
circumstance,  coupled  with  the  fact  of  the  Labyrinthodon  having  existed 
at  the  period  when  the  Cheirotherium  footsteps  were  made,  was  the  first 
step  towards  the  identification  of  those  tracks  with  the  newly-discovered 
Batrachian.  It  was  at  the  same  time  observed  that  the  footmarks  of 
Cheirotherium  were  more  like  those  of  toads  than  of  any  other  living  ani- 
mal ;  and,  lastly,  that  the  size  of  the  three  species  of  Labyrinthodon 
corresponded  with  the  size  of  three  different  kinds  of  footprints  which 
had  already  been  supposed  to  belong  to  three  distinct  Cheirotheria.  It 
was  moreover  inferred,  with  confidence,  that  the  Labyrinthodon  was  an 
air-breathing  reptile  from  the  structure  of  the  nasal  cavity,  in  which  the 
posterior  outlets  were  at  the  back  part  of  the  mouth,  instead  of  being 
directly  under  the  anterior  or  external  nostrils.  It  must  have  respired  air 
after  the  manner  of  saurians,  and  may  therefore  have  imprinted  on  the 
shore  those  footsteps,  which,  as  we  have  seen,  could  not  have  originated 
from  an  animal  walking  under  water. 

It  is  true  that  the  structure  of  the  foot  is  still  wanting,  and  that  a  more 
connected  and  complete  skeleton  is  required  for  demonstration ;  but  the 
circumstantial  evidence  above  stated  is  strong  enough  to  produce  the 


340  FOSSILS  EEMAINS  OF  LABYRrNTHOIHDN.       [Cn.  XXII 

conviction  that  the  Cheirotherium  and  Ldbyrinthodon  are  one  and  the 
same. 

In  order  to  show  the  manner  in  which  one  of  these  formidable  Batra- 
chians  may  have  impressed  the  mark  of  its  feet  upon  the  shore,  Prof. 
Owen  has  attempted  a  restoration,  of  which  a  reduced  copy  is  annexed 


Fig.  439. 


Eestored  outline  of  Labyrinthodon  pachygnathm,  Owen. 

The  only  bones  of  this  species  at  present  known  are  those  of  the  head; 
the  pelvis,  and  part  of  the  scapula,  which  are  shown  by  stronger  lines  in 
the  above  figure.  There  is  reason  for  believing  that  the  head  was  not 
smooth  externally,  but  protected  by  bony  scutella.  This  character  and 
the  presence  of  strong  conical  teeth  implanted  in  sockets,  together  with 
the  elongated  form  of  the  head,  induce  many  able  anatomists,  such  as 
Von  Meyer  and  Mantell,  to  regard  the  Labyrinthodons  as  more  allied  to 
crocodiles  than  to  frogs.  But  the  double  occipital  condyles,  the  position 
of  some  of  the  teeth  on  the  vomer  and  palatine  bones,  and  other  charac- 
ters, are  considered  by  Messrs.  Jager  and  Owen  to  give  them  superior 
claims  to  be  classed  as  batrachians.  That  they  occupy  an  intermediate 
place  is  clear,  but  too  little  is  yet  known  of  the  entire  skeleton  to  enable 
us  to  determine  the  exact  amount  of  their  affinity  to  one  or  other  of  the 
above-named  great  divisions  of  reptiles. 

Triassic  Mammifer  (Microlestes  antiquus,  Plieninger). — In  the  year 
1847,  Professor  Plieninger,  of  Stuttgart,  published  a  description  of  two 
fossil  molar  teeth,  referred  by  him  to  a  warm-blooded  quadruped,*  which 
he  obtained  from  a  bone-breccia  in  Wiirtemberg  occurring  between  the 
lias  and  the  keuper.  As  the  announcement  of  so  novel  a  fact  has  never 
met  with  the  attention  it  deserved,  we  are  indebted  to  Dr.  Jager,  of  Stutt- 
gart, for  having  recently  reminded  us  of  it  in  his  Memoir  on  the  Fossil 
Mammalia  of  Wiirtemberg.f 

Fig.  440  represents  the  tooth  first  found,  taken  from  the  plate  pub- 
lished in  1847,  by  Professor  Plieninger ;  and  fig.  441  is  a  drawing  of  the 
same  executed  from  the  original  by  Mr.  Hermann  Von  Meyer,  which  he 
has  been  kind  enough  to  send  me.  Fig.  442  is  a  second  and  larger 
molar,  copied  from  Dr.  Jager's  plate  Ixxi.,  fig.  15. 

*  "Wiirtembergisch.  Naturwissen  Jahreshefte,  3  Jahr.  Stuttgart,  1847. 
f  Nov.  Act.  Acad.  Caesar.  Leopold.  Nat.  Cur.  1850,  p.  902.    For  figures,  see 
ibid,  plate  xxi.  figs.  14,  15,  1&,  17. 


CH.  XXIL]  FOSSIL   MAMMIFER  IN  TRIAS. 

Fig.  440. 


341 


Jfict'olestes  antiquus,  Plieninger.  Molar  tooth  magni- 
fied. Upper  Trias,  Diegerloch,  near  Stuttgart,  Wiir- 
ttmberg. 

a.  View  of  inner  side  ?  &.  Same,  outer  side  ? 

c,.  Same  in  profile.  d.  Crown  of  same. 


Molar  of  Mivroles- 
tent  Plien.4times 
as  large  as  the  fig. 
440.  From  the 
trias  of  Diegerloch, 
Stuttgart 


Microleste*  antiquu^ 
Plien.       . 

View  of  same  molar 
as  No.  440.    From  & 
drawing     by     Her- 
mann Von  Meyer, 
a.    View    of    inner 

side? 
&.  Crown  of  same. 


Professor  Plieninger  inferred  in   1847,  from   the  Fig.  442. 

double  fangs  of  this  tooth  and  their  unequal  size,  and  — 

from  the  form  and  number  of  the  protuberances  or 
cusps  on  the  flat  crowns,  that  it  was  the  molar  of  a 
Mammifer;  and  considering  it  as  predaceous,  prob- 
ably insectivorous,  he  calls  it  Microlestes,  from  pxpos, 
little,  and  X^o^s,  a  beast  of  prey.  Soon  afterwards, 
he  found  the  second  tooth,  also  at  the  same  locality, 
Diegerloch,  about  two  miles  to  the  southeast  of  Stutt- 
gart. Some  of  its  cusps  are  broken,  but  there  seem 
to  have  been  six  of  them  originally.  From  its  agree- 
ment in  general  characters,  it  is  supposed  by  Professor 
Plieninger  to  be  referable  to  the  same  animal,  but  as  it  is  four  times  as 
big,  it  may  perhaps  have  belonged  to  another  allied  species.  This  molar 
is  attached  to  the  matrix  consisting  of  sandstone,  whereas  the  tooth,  fig. 
440,  is  isolated.  Several  fragments  of  bone,  differing  in  structure  from 
that  of  the  associated  saurians  and  fish,  and  believed  to  be  mammalian, 
were  imbedded  near  them  in  the  same  rock. 

Mr.  Waterhouse  of  the  British  Museum,  after  studying  the  annexed 
figs.  440,  441,  442,  and  the  descriptions  of  Prof.  Plieninger,  observes, 
that  not  only  the  double  roots  of  the  teeth,  and  their  crowns  presenting 
several  cusps,  resemble  those  of  Mammalia,  but  the  cingulum  also,  or 
ridge  surrounding  the  base  of  that  part  of  the  body  of  the  tooth  which 
was  exposed  or  above  the  gum,  is  a  character  distinguishing  them  from 
fish  and  reptiles.  "  The  arrangement  of  the  six  cusps  or  tubercles  in  two 
rows,  in  fig.  440,  with  a  groove  or  depression  between  them,  and  the 
oblong  form  of  the  tooth,  lead  him,  he  says,  to  regard  it  as  a  molar  of  the 
lower  jaw.  Both  the  teeth  differ  from  those  of  the  Stonesfield  Mammalia, 
but  do  not  supply  sufficient  data  for  determining  to  what  order  they  be- 
longed. 

Professor  Plieninger  has  sent  me  a  cast  of  the  smaller  tooth,  which 
exhibits  well  the  characteristic  mammalian  test,  the  double  fang;  but 
Prof.  Owen,  to  whom  I  have  shown  it,  is  not  able  to  recognize  its  affinity 
with  any  mammalian  type,  recent  or  extinct,  known  to  him. 

It  has  already  been  stated  that  the  stratum  in  which  the  above-men- 
tioned fossils  occur  is  intermediate  between  the  lias  and  the  uppermost 


34:2  ORIGIN  OF  RED  SANDSTONE  [On,  XXII 

member  of  the  trias.  That  it  is  really  triassic  may  be  deduced  from  the 
following  considerations.  In  Wurtemberg  there  are  two  "  bone-beds," 
one  of  great  extent,  and  very  rich  in  the  remains  of  fish  and  reptiles, 
which  intervenes  between  the  muschelkalk  and  keuper ;  the  other,  con- 
taining the  Microlestes,  less  extensive  and  fossiliferous,  which  rests  on  the 
keuper,  or  superior  member  of  the  trias,  and  is  covered  by  the  sandstone 
of  the  lias.  The  last-mentioned  breccia,  therefore,  occupies  nearly  the 
same  place  as  the  well-known  English  "  bone-bed"  of  Axmouth  and  Aust- 
cliff  near  Bristol,  which  is  shown  above,  p.  336,  to  include  characteristic 
species  of  muschelkalk  fish,  of  the  genus  Saurichthys,  Hylodus,  and 
Gyrolepis.  In  both  the  Wurtemberg  bone-beds  these  three  genera  are 
also  found,  and  one  of  the  species,  Saurichthys  Mougeotii,  is  common  to 
both  the  lower  and  upper  breccias,  as  is  also  a  remarkable  reptile  called 
Nothosaurus  miraUlis.  The  saurian  called  Belodon  by  H.  Von  Meyer, 
of  the  Thecodont  family,  is  another  triassic  form,  associated  at  Diegerloch 
with  Microlestes. 

Previous  to  this  discovery  of  Professor  Plieninger,  the  mat  ancient 
of  known  fossil  Mammalia  were  those  of  the  Stonesfield  slate,  above  de- 
scribed, p.  310,  no  representation  of  this  class  having  as  yet  been  met  with 
in  the  Fuller's  earth,  or  inferior  Oolite,  nor  in  any  member  of  the  Lias. 

Origin  of  Red  Sandstone  and  Rock-Salt. 

We  have  seen  that,  in  various  parts  of  the  world,  red  and  mottled 
clays,  and  sandstones,  of  several  distinct  geological  epochs,  are  found 
associated  with  salt,  gypsum,  magnesian  limestone,  or  with  one  or  all  of 
these  substances.  There  is,  therefore,  in  all  likelihood,  a  general  cause 
for  such  a  coincidence.  Nevertheless,  we  must  not  forget  that  there  are 
dense  masses  of  red  and  variegated  sandstones  and  clays,  thousands  of 
feet  in  thickness,  and  of  vast  horizontal  extent,  wholly  devoid  of  saliferous 
or  gypseous  matter.  There  are  also  deposits  of  gypsum  and  of  muriate  of 
soda,  as  in  the  blue  clay  formation  of  Sicily,  without  any  accompanying 
red  sandstone  or  red  clay. 

To  account  for  deposits  of  red  mud  and  red  sand,  we  have  simply  to 
suppose  the  disintegration  of  ordinary  crystalline  or  metamorphic  schists. 
Thus,  in  the  Eastern  Grampians  of  Scotland,  in  the  north  of  Forfarshire, 
for  example,  the  mountains  of  gneiss,  mica-schist,  and  clay-slate,  are  over- 
spread with  alluvium,  derived  from  the  disintegration  of  those  rocks ;  and 
the  mass  of  detritus  is  stained  by  oxide  of  iron,  of  precisely  the  same  color 
as  the  Old  Red  Sandstone  of  the  adjoining  Lowlands.  Now  this  alluvium 
merely  requires  to  be  swept  down  to  the  sea,  or  into  a  lake,  to  form  strata 
of  red  sandstone  and  red  marl,  precisely  like  the  mass  of  the  "  Old  Red" 
or  New  Red  systems  of  England,  or  those  tertiary  deposits  of  Auvergne 
(see  p.  199),  before  described,  which  are  in  lithological  characters  quite 
undistinguishable.  The  pebbles  of  gneiss  in  the  Eocene  red  sandstone  of 
Auvergne  point  clearly  to  the  rocks  from  which  it  has  been  derived.  The 
red  coloring  matter  may,  as  in  the  Grampians,  have  been  furnished  by  the 


CH.  XXII]  AND  ROCK  SALT.  343 

decomposition  of  hornblende  or  mica,  which  contain  oxide  of  iron  in 
large  quantity. 

It  is  a  general  fact,  and  one  not  yet  accounted  for,  that  scarcely  any 
fossil  remains  are  preserved  in  stratified  rocks  on  which  this  oxide  of 
iron  abounds ;  and  when  we  find  fossils  in  the  New  or  Old  Eed  Sand- 
stone in  England,  it  is  in  the  gray,  and  usually  calcareous  beds  that 
they  occur. 

The  gypsum  and  saline  matter,  occasionally  interstratified  with  such 
red  clays  and  sandstones  of  various  ages,  primary,  secondary,  and  ter- 
tiary, have  been  thought  by  some  geologists  to  be  of  volcanic  origin. 
Submarine  and  subaerial  exhalations  often  occur  in  regions  of  earth- 
quakes and  volcanoes  far  from  points  of  actual  eruption,  and  charged 
with  sulphur,  sulphuric  salts,  and  with  common  salt  and  muriate  of  soda. 
In  a  word,  such  "  solfataras"  are  vents  by  which  all  the  products  which 
issue  in  a  state  of  sublimation  from  the  craters  of  active  volcanoes,  obtain 
a  passage  from  the  interior  of  the  earth  to  the  surface.  That  such  gaseous 
emanations  and  mineral  springs,  impregnated  with  the  ingredients  before 
enumerated,  and  often  intensely  heated,  continue  to  flow  out  unaltered  in 
composition  and  temperature  for  ages,  is  well  known.  But  before  we  can 
decide  on  their  real  instrumentality  in  producing  in  the  course  of  ages 
beds  of  gypsum,  salt,  and  dolomite,  we  require  to  know  more  respecting 
the  chemical  changes  actually  in  progress  in  seas  where  volcanic  agency 
is  at  work. 

The  origin  of  rock-salt,  however,  is  a  problem  of  so  much  interest  in 
theoretical  geology  as  to  demand  the  discussion  of  another  hypothesis 
advanced  on  the  subject ;  namely,  that  which  attributes  the  precipitation 
of  the  salt  to  evaporation,  whether  of  inland  lakes  or  of  lagoons  com- 
municating with  the  ocean. 

At  Northwich,  in  Cheshire,  two  beds  of  salt,  in  great  part  unmixed 
with  earthy  matter,  attain  the  extraordinary  thickness  of  90  and  even 
100  feet.  The  upper  surface  of  the  highest  bed  is  very  uneven,  forming 
cones  and  irregular  figures.  Between  the  two  masses  there  intervenes  a 
bed  of  indurated  clay,  traversed  with  veins  of  salt.  The  highest  bed 
thins  off  towards  the  southwest,  losing  15  feet  in  thickness  in  the  course 
of  a  mile.*  The  horizontal  extent  of  these  particular  masses  in  Cheshire 
and  Lancashire  is  not  exactly  known ;  but  the  area,  containing  saliferous 
clays  and  sandstones,  is  supposed  to  exceed  150  miles  in  diameter,  while 
the  total  thickness  of  the  trias  in  the  same  region  is  estimated  by  Mr. 
Ormerod  at  more  tian  1700  feet.  Ripple-marked  sandstones,  and  the 
footprints  of  animais,  before  described,  are  observed  at  so  many  levels 
that  we  may  safely  assume  the  whole  area  to  have  undergone  a  slow  and 
gradual  depression  during  the  formation  of  the  R«d  Sandstone.  The  evi- 
dence of  such  a  movement,  wholly  independent  of  the  presence  of  salt 
itself,  is  very  important  in  reference  to  the  theory  under  consideration. 

In  the  "Principles  of  Geology"  (chap.  27),  I  published  a  map,  fur- 

*  Ormerod,  Quart  Geol.  Journ.  1848,  vol.  iv.  p.  277. 


344  RUNN   OF   CUTC1I.  [On.  XXII 

nished  to  me  by  the  late  Sir  Alexander  Burnes,  of  that  singular  flat 
region  called  the  Runn  of  Cutch,  near  the  delta  of  the  Indus,  which  is 
7000  square  miles  in  area,  or  equal  in  extent  to  about  one-fourth  of  Ire- 
land. It  is  neither  land  nor  sea,  but  is  dry  during  a  part  of  every  year, 
and  .again  covered  by  salt  water  during  the  monsoons.  Some  parts  of 
it  are  liable,  after  long  intervals,  to  be  overflowed  by  river-water.  Its 
surface  supports  no  grass,  but  is  incrusted  over,  here  and  there,  by  a 
layer  of  salt,  about  an  inch  in  depth,  caused  by  the  evaporation  of  sea- 
water.  Certain  tracts  have  been  converted  into  dry  land  by  upheaval 
during  earthquakes  since  the  commencement  of  the  present  century,  and, 
in  other  directions,  the  boundaries  of  the  Runn  have  been  enlarged  by 
subsidence.  That  successive  layers  of  salt  might  be  thrown  down,  one 
upon  the  other,  over  thousands  of  square  miles,  in  such  a  region,  is  un- 
deniable. The  supply  of  brine  from  the  ocean  would  be  as  inexhausti- 
ble as  the  supply  of  heat  from  the  sun  to  cause  evaporal'on.  The  only 
assumption  required  to  enable  us  to  explain  a  great  thickness  of  salt  in 
such  an  area  is,  the  continuance,  for  an  indefinite  period,  of  a  subsiding 
movement,  the  country  preserving  all  the  time  a  general  approach  to 
horizontal!  ty.  Pure  salt  could  only  be  formed  in  the  central  parts  of 
basins,  where  no  sand  could  be  drifted  by  the  wind,  or  sediment  be 
brought  by  currents.  Should  the  sinking  of  the  ground  be  accelerated, 
so  as  to  let  in  the  sea  freely,  and  deepen  the  water,  a  temporary  suspen- 
sion of  the  precipitation  of  salt  would  be  the  only  result.  On  the  other 
hand,  if  the  area  should  dry  up,  ripple-marked  sands  and  the  footprints 
of  animals  might  be  formed,  where  salt  had  previously  accumulated. 
According  to  this  view  the  thickness  of  the  salt,  as  well  as  of  the  accom- 
panying beds  of  mud  and  sand,  becomes  a  mere  question  of  time,  or 
requires  simply  a  repetition  of  similar  operations. 

Mr.  Hugh  Miller,  in  an  able  discussion  of  this  question,  refers  to  Dr. 
Frederick  Parrot's  account,  in  his  journey  to  Ararat  (1836),  of  the  salt 
lakes  of  Asia.  In  several  of  these  lakes  west  of  the  river  Manech,  "  the 
water,  during  the  hottest  season  of  the  year,  is  covered  on  its  surface 
with  a  crust  of  salt  nearly  an  inch  thick,  which  is  collected  with  shovels 
into  boats.  The  crystallization  of  the  salt  is  effected  by  rapid  evapora- 
tion from  the  sun's  heat  and  the  supersaturation  of  the  water  with  mu- 
riate of  soda  ;  the  lake  being  so  shallow  that  the  little  boats  trail  on  the 
bottom  and  leave  a  furrow  behind  them,  so  that  the  lake  must  be  re- 
garded as  a  wide  pan  of  enormous  superficial  extent,  in  which  the  brine 
can  easily  reach  the  degree  of  concentration  required." 

Another  traveller,  Major  Harris,  in  his  "  Highlands  of  Ethiopia,"  de- 
scribes a  salt  lake,  called  the  Bahr  Assal,  near  the  Abyssinian  frontier, 
which  once  formed  the  prolongation  of  the  Gulf  of  Tadjara,  but  was 
afterwards  cut  off  from  the  gulf  by  a  broad  bar  of  lava  or  of  land  up- 
raised by  an  earthquake.  "  Fed  by  no  rivers,  and  exposed  in  a  burning 
climate  to  the  unmitigated  rays  of  the  sun,  it  has  shrunk  into  an  ellipti- 
cal basin,  seven  miles  in  its  transverse  axis,  half  filled  with  smooth  water, 
of  the  deepest  cerulean  hue,  and  half  with  a  solid  sheet  of  glittering 


CH.  XXII]  SALTXESS   OF   THE   KED   SEA.  345 

snow-white  salt,  the  offspring  of  evaporation."  "If,"  says  Mr.  Hugh 
Miller,  "  we  suppose,  instead  of  a  barrier  of  lava,  that  sand-bars  were 
raised  by  the  surf  on  a  flat  arenaceous  coast  during  a  slow  and  equable 
sinking  of  the  surface,  the  waters  of  the  outer  gulf  might  occasionally 
topple  over  the  bar,  and  supply  fresh  brine  when  the  first  stock  had  been 
exhausted  by  evaporation."* 

We  may  add  that  the  permanent  impregnation  of  the  waters  of  a 
large  shallow  basin  with  salt,  beyond  the  proportion  which  is  usual  in 
the  ocean,  would  cause  it  to  be  uninhabitable  by  mollusks  or  fish,  as  is  the 
case  in  the  Dead  Sea,  and  the  muriate  of  soda  might  remain  in  excess, 
even  though  it  were  occasionally  replenished  by  irruptions  of  the  sea. 
Should  the  saline  deposit  be  eventually  submerged,  it  might,  as  we  have 
seen  from  the  example  of  the  Runn  of  Cutch,  be  covered  by  a  freshwater 
formation  containing  fluviatile  organic  remains ;  and  in  this  way  the 
apparent  anomaly  of  beds  of  sea-salt  and  clays  devoid  of  marine  fossils, 
alternating  with  others  of  freshwater  origin,  may  be  explained. 

Dr.  G.  Buist,  in  a  recent  communication  to  the  Bombay  Geographical 
Society  (vol.  ix.),  has  asked  how  it  happens  that  the  Red  Sea  should  not 
exceed  the  open  ocean  in  saltness,  by  more  than  ^th  Per  cen*-  ^^e  ^e(^ 
Sea  receives  no  supply  of  water  from  any  quarter  save  through  the 
Straits  of  Babelmandeb ;  and  there  is  not  a  single  river  or  rivulet  flowing 
into  it  from  a  circuit  of  4000  miles  of  shore.  The  countries  around  are 
all  excessively  sterile  and  arid,  and  composed,  for  the  most  part,  of  burn- 
ing deserts.  From  the  ascertained  evaporation  in  the  sea  itself,  Dr. 
Buist  computes  that  nearly  8  feet  of  pure  water  must  be  carried  off  from 
the  whole  of  its  surface  annually,  this  being  probably  equivalent  to  -5-^  th 
part  of  its  whole  volume.  The  Red  Sea,  therefore,  ought  to  have  1  per 
cent,  added  annually  to  its  saline  contents ;  and  as  these  constitute  4 
per  cent,  by  weight,  or  2J  per  cent,  in  volume  of  its  entire  mass,  it 
ought,  assuming  the  average  depth  to  be  800  feet,  which  is  supposed  to 
be  far  beyond  the  truth,  to  have  been  converted  into  one  solid  salt 
formation  in  less  than  3000  years.f  Does  the  Red  Sea  receive  a  supply 
of  water  from  the  ocean,  through  the  narrow  Straits  of  Babelmandeb, 
sufficient  to  balance  the  loss  by  evaporation  ?  And  is  there  an  under- 
current of  heavier  saline  water  annually  flowing  outwards  ?  If  not,  in 
what  manner  is  the  excess  of  salt  disposed  of  ?  An  investigation  of  this 
subject  by  our  nautical  surveyors  may  perhaps  aid  the  geologist  in  fram- 
ing a  true  theory  of  the  origin  of  rock-salt. 


On  the  New  Red  Sandstone  of  the  valley  of  the  Connecticut  River  in 
the  United  States. 

In  a  depression  of  the  granitic  or  hypogene  rocks  in  the  States  of 
Massachusetts  and  Connecticut,  strata  of  red  sandstone,  shale,  and  con- 

*  Hugh  Miller,  First  Impressions  of  England,  1847,  pp.  183,  214. 
f  Buist,  Trans,  of  Bombay  Geograph.  Soc.  1850,  vol.  ix.  p.  38. 


346  NEW  BED  SANDSTONE   OF  THE   U.   STATES.         [Cn.  XXII. 

glomerate  are  found  occupying  an  area  more  than  150  miles  in  length 
from  north  to  south,  and  about  5  to  10  miles  in  breadth,  the  beds  dipping 
to  the  eastward  at  angles  varying  from  5  to  50  degrees.  The  extreme 
inclination  of  50  degrees  is  rare,  and  only  observed  in  the  neighborhood 
of  masses  of  trap  which  have  been  intruded  into  the  red  sandstone  while 
it  was  forming,  or  before  the  newer  parts  of  vhe  deposit  had  been  com- 
pleted. Having  examined  this  series  of  rocks  in  many  places,  I  feel 
satisfied  that  they  were  formed  in  shallow  water,  and  for  the  most  part 
near  the  shore,  and  that  some  of  the  beds  were  from  time  to  time  raised 
above  the  level  of  the  water,  and  laid  dry,  while  a  newer  series,  composed 
of  similar  sediment,  was  forming.  The  red  flags  of  thin-bedded  sandstone 
are  often  ripple-marked,  and  exhibit  on  their  under  sides  casts  of  cracks 
formed  in  the  underlying  red  and  green  shales.  These  last  must  have 
shrunk  by  drying  before  the  sand  was  spread  over  them.  On  some 
shales  of  the  finest  texture  impressions  of  rain-drops  may  be  seen,  and 
casts  of  them  in  the  incumbent  argillaceous  sandstones.  Having  observed 
similar  markings  produced  by  showers,  of  which  the  precise  date  was 
known,  on  the  recent  red  mud  of  the  Bay  of  Fundy,  and  casts  in  relief 
of  the  same,  on  layers  of  dried  mud  thrown  down  by  subsequent  tides,* 
I  feel  no  doubt  in  regard  to  the  origin  of  some  of  the  ancient  Connecticut 
impressions.  I  have  also  seen  on  the  mud-flats  of  the  Bay  of  Fundy  the 
footmarks  of  birds  (Tringa  minuta},  which  daily  run  along  the  borders 
of  that  estuary  at  low  water,  and  which  I  have  described  in  my  Travels.f 
Similar  layers  of  red  mud,  now  hardened  and  compressed  into  shale,  are 
laid  open  on  the  banks  of  the  Connecticut,  and  retain  faithfully  the  im- 
pressions and  casts  of  the  feet  of  numerous  birds  and  reptiles  which 
walked  over  them  at  the  time  when  they  were  deposited,  probably  in  the 
Triassic  Period. 

According  to  Prof.  Hitchcock,  the  footprints  of  no  less  than  thirty-two 
species  of  bipeds,  and  twelve  of  quadrupeds,  have  been  already  detected 
in  these  rocks.  Thirty  of  these  are  believed  to  be  those  of  birds,  four  of 
lizards,  two  of  chelonians,  and  six  of  batrachians.  The  tracks  have  been 
found  in  more  than  twenty  places,  scattered  through  an  extent  of  nearly 
80  miles  from  north  to  south,  and  they  are  repeated  through  a  succession 
of  beds  attaining  at  some  points  a  thickness  of  more  than  1000  feet, 
which  may  have  been  thousands  of  years  in  forming. J 

As  considerable  skepticism  is  naturally  entertained  in  regard  to  the 
nature  of  the  evidence  derived  from  footprints,  it  may  be  well  to  enume- 
rate some  facts  respecting  them  on  which  the  faith  of  the  geologist  may 
rest.  When  I  visited  the  United  States  in  1842,  more  than  2000  im- 
pressions had  been  observed  by  Professor  Hitchcock,§  in  the  district 
alluded  to,  and  all  of  them  were  indented  on  the  upper  surface  of  the 
layers  while  the  corresponding  casts,  standing  out  in  relief,  were  always 

*  Principles  of  Geol.  9th  ed.  p.  203. 
f  Travels  m  North  America,  vol.  ii.  p.  168. 
J  Hitchcock,  Mem.  of  Amer.  Acad.  New  Ser.  vol.  iii.  p.  129. 
See  also  Mem.  Amer.  Ac.  vol.  iii.  1848. 


CH.  XXII.] 


FOSSIL  FOOT! BINTS   IX   CONNECTICUT. 


347 


on  the  lower  surfaces  or  planes  of  the  strata.     If  we  follow  a  single  line 
of  marks,  we  find  them  uniform  in  size,  and  nearlv 

/ 1^  uniform  in  distance  from  each  other,  the  toes  of  two 

successive  footprints,  turning  alternately  right  and 
left  (see  fig.  443).  Such  single  lines  indicate  a  biped ; 
and  there  is  generally  such  a  deviation  from  a  straight 
line,  in  any  three  successive  prints,  as  we  remark  in 
the  tracks  left  by  birds.  There  is  also  a  striking  re- 
lation between  the  distance  separating  two  footprints 
in  one  series  and  the  size  of  the  impressions ;  in  other 
words,  an  obvious  proportion  between  the  length  01 
the  stride  and  the  dimension  of  the  creature  which 
walked  over  the  mud.  If  the  marks  are  small,  they 
may  be  half  an  inch  asunder ;  if  gigantic,  as,  for  ex- 
ample, where  the  toes  are  20  inches  long,  they  are 
occasionally  4  feet  and  a  half  apart.  The  bipedal 
impressions  are  for  the  most  part  trifid,  and  show 
the  same  number  of  joints  as  exist  in  the  feet  of  liv- 
ing tridactylous  birds.  Now  such  birds  have  three 
phalangeal  bones  for  the  inner  toe,  four  for  the  middle, 
and  five  for  the  outer  one  (see  fig.  443) ;  but  the  im- 
pression of  the  terminal  joint  is  that  of  the  nail  only. 
The  fossil  footprints  exhibit  regularly,  where  the 
joints  are  seen,  the  same  number;  and  we  see  in 
each  continuous  line  of  tracks  the  three-jointed  and 
nersinFaiis,a Valley  of  five-jointed  toes  placed  alternately  outwards,  first  on 
Dr.  ^eane^Mem^f the  one  side  and  ^^  °n  the  other.  In  some  speci- 
Acad.  vol.  iv.  mens,  besides  impressions  of  the  three  toes  in  front, 
the  rudiment  is  seen  of  the  fourth  toe  behind.  It  is 
not  often  that  the  matrix  has  been  fine  enough  to  retain  impressions  of 
the  integument  or  skin  of  the  foot ;  but  in  one  fine  specimen  found  at 
Turner's  Falls  on  the  Connecticut,  by  Dr.  Deane,  these  markings  are  well 
preserved,  and  have  been  recognized  by  Prof.  Owen  as  resembling  the 
skin  of  the  ostrich,  and  not  that  of  reptiles.*  Much  care  is  required  to 
ascertain  the  precise  layer  of  a  laminated  rock  on  which  an  animal  has 
walked,  because  the  impression  usually  extends  downwards  through  sev- 
eral laminae  ;  and  if  the  upper  layer  originally  trodden  upon  is  wanting, 
the  mark  of  one  or  more  joints,  or  even  in  some  cases  an  entire  toe,  which 
sank  less  deep  into  the  soft  ground,  may  disappear,  and  yet  the  remainder 
of  the  footprint  be  well  defined. 

The  size  of  several  of  the  fossil  impressions  of  the  Connecticut  red  sand- 
stone so  far  exceeds  that  of  any  living  ostrich,  that  naturalists  at  first 
were  extremely  adverse  to  the  opinion  of  their  having  been  made  by 
birds,  until  the  bones  and  almost  entire  skeleton  of  the  Dinornis  and  of 

*  This  specimen  was  in  the  late  Dr.  Mantell's  museum,  and  indicated  a  bird 
of  a  size  intermediate  between  the  small  and  the  largest  of  the  Connecticut 
gpecies. 


348  FOSSIL  FOOTPKINTS  IK  THE  [On.  XXII. 

other  feathered  giants  of  New  Zealand  were  discovered.  Their  dimen- 
sions have  at  least  destroyed  the  force  of  this  particular  objection.  The 
magnitude  of  the  impressions  of  the  feet  of  a  heavy  animal,  which  has 
walked  on  soft  mud,  increases  for  some  distance  below  the  surface  origi- 
nally trodden  upon.  In  order,  therefore,  to  guard  against  exaggeration, 
the  casts  rather  than  the  mould  are  relied  on.  These  casts  show  that 
some  of  the  fossil  bipeds  had  feet  four  times  as  large  as  the  ostrich,  but 
not  perhaps  much  larger  than  the  Dinornis. 

The  eggs  of  another  gigantic  bird,  called  ^Epiornis,  which  has  proba- 
bly been  exterminated  by  man,  have  recently  been  discovered  in  an 
alluvial  deposit  in  Madagascar.  The  egg  has  six  times  the  capacity  of 
that  of  the  ostrich  ;  but,  judging  from  the  large  size  of  the  egg  of  the 
Apterix,  Professor  Owen  does  not  believe  thai  the  ^Epiornis  exceeded,  if 
indeed  it  equalled,  the  Dinornis  in  stature. 

Among  the  supposed  bipedal  tracks,  a  single  distinct  example  only  has 
been  observed  of  feet  in  which  there  are  four  toes  directed  forwards.  In 
this  case  a  series  of  four  footprints  is  seen,  each  22  inches  long  and 
12  wide,  with  joints  much  resembling  those  in  the  toes  of  birds.  Pro- 
fessor Agassiz  has  suggested  that  it  might  have  belonged  to  a  gigantic 
bipedal  batrachian.  Other  naturalists  have  called  our  attention  to  the 
fact,  that  some  quadrupeds,  when  walking,  place  the  hind  foot  so  precisely 
on  the  spot  just  quitted  by  the  fore  foot,  as  to  produce  a  single  line  of 
imprints,  like  those  of  a  biped ;  and  Mr.  Waterhouse  Hawkins  has  re- 
marked that  certain  species  of  frogs  and  lizards  in  Australia  have  the  two 
outer  toes  so  slightly  developed  and  so  much  raised  that  they  might  leave 
tridactylous  footprints  on  mud  and  sand.  Another  osteologist,  Dr.  Leidy, 
in  the  United  States,  observed  to  me  that  the  pterodactyl  was  a  bipedal 
reptile  approaching  the  bird  so  nearly  in  the  structure  and  shape  of  its 
wing-bones  and  tibiae,  that  some  of  these  last,  obtained  from  the  Chalk 
and  Wealden  in  England,  had  been  mistaken  by  the  highest  authorities 
for  true  birds'  bones.  May  not  the  foot,  therefore,  of  a  pterodactyl  have 
equally  resembled  that  of  a  bird  ?  Be  this  as  it  may,  the  greater  num- 
ber of  the  American  impressions  agree  so  precisely  in  form  and  size  with 
the  footmarks  of  known  living  birds,  especially  with  those  of  waders, 
that  we  shall  act  most  in  accordance  with  known  analogies  by  re- 
ferring most  of  them  at  present  to  feathered,  rather  than  to  featherless 
bipeds. 

No  bones  have  as  yet  been  met  with,  whether  of  pterodactyl  or  bird, 
in  the  rocks  of  the  Connecticut,  but  there  are  numerous  coprolites  ;  and 
an  ingenious  argument  has  been  derived  by  Dr.  Dana  from  the  analysis 
of  these  bodies,  and  the  proportion  they  contain  of  uric  acid,  phosphate  of 
lime,  carbonate  of  lime,  and  organic  matter,  to  show  that,  like  guano, 
they  are  the  droppings  of  birds,  rather  than  of  reptiles. 

Some  of  the  quadrupedal  footprints  which  accompany  those  of  birds 
are  analogous  to  European  Ckeirotheria,  and  with  a  similar  disproportion 
between  the  hind  and  fore  feet.  Others  resemble  that  remarkable  rep- 
tile, the  Rhyncosaurus  of  the  English  Trias,  a  creature  having  some 


On.  XXII]  VALLEY  OF  THE  CONNECTICUT.  349 

relation  in  its  osteology  both  to  chelonians  and  birds.  Other  imprints, 
again,  are  like  those  of  turtles. 

Mr.  Darwin,  in  his  "  Journal  of  a  Voyage  in  the  Beagle,"  informs  us 
that  the  "  South  American  ostriches,  although  they  live  on  vegetable 
matter,  such  as  roots  and  grass,  are  repeatedly  seen  at  Bahia  Blanca  (lat. 
39°  S.),  on  the  coast  of  Buenos  Ayres,  coming  down  at  low  water  to 
the  extensive  mud-banks  which  are  then  dry,  for  the  sake,  as  the  Gauchos 
say,  of  feeding  on  small  fish."  They  readily  take  to  the  water,  and 
have  been  seen  at  the  bay  of  San  Bias,  and  at  Port  Valdez,  in  Patago- 
nia, swimming  from  island  to  island.*  It  is  therefore  evident,  that  in 
our  times  a  South  American  mud-bank  might  be  trodden  simultaneously 
by  ostriches,  alligators,  tortoises,  and  frogs ;  and  the  impressions  left,  in 
the  nineteenth  century,  by  the  feet  of  these  various  tribes  of  animals, 
would  not  differ  from  each  other  more  entirely  than  do  those  attributed 
to  birds,  saurians,  chelonians,  and  batrachians,  in  the  rocks  of  the  Con- 
necticut. 

To  determine  the  exact  age  of  the  red  sandstone  and  shale  containing 
these  ancient  footprints  in  the  United  States,  is  not  possible  at  present. 
No  fossil  shells  have  yet  been  found  in  the  deposit,  nor  plants  in  a  de- 
terminable  state.  The  fossil  fish  are  numerous  and  very  perfect ;  but 
they  are  of  a  peculiar  type,  which  was  originally  referred  to  the  genus 
Palceoniscus,  but  has  since,  with  propriety,  been  ascribed,  by  Sir  Philip 
Egerton,  to  a  new  genus.  To  this  he  has  given  the  name  of  Ischypterus, 
from  the  great  size  and  strength  of  the  fulcral  rays  of  the  dorsal  fin 
(from  iti^s,  strength,  and  tfrspov,  a  fin).  They  differ  from  Palceoniscus, 
as  Mr.  Redfield  first  pointed  out,  by  having  the  vertebral  column  pro- 
longed to  a  more  limited  extent  into  the  upper  lobe  of  the  tail,  or,  in 
the  language  of  M.  Agassiz,  they  are  less  heterocercal.  The  teeth  also, 
according  to  Sir  P.  Egerton,  who,  in  1844,  examined  for  me  a  fine  series 
of  specimens  which  I  procured  at  Durham,  Connecticut,  differ  from  those 
of  Palceoniscus  in  being  strong  and  conical. 

That  the  sandstones  containing  these  fish  are  of  older  date  than  the 
strata  containing  coal,  before  described  (p.  330)  as  occurring  near  Rich- 
mond in  Virginia,  is  highly  probable.  These  were  shown  to  be  as  old 
at  least  as  the  oolite  and  lias.  The  higher  antiquity  of  the  Connecticut 
beds  cannot  be  proved  by  direct  superposition,  but  may  be  presumed 
from  the  general  structure  of  the  country.  That  structure  proves  them 
to  be  newer  than  the  movements  to  which  the  Appalachian  or  AUeghany 
chain  owes  its  flexures,  and  this  chain  includes  the  ancient  coal  forma- 
tion among  its  contorted  rocks.  The  unconformable  position  of  this  New 
Red  with  ornithicnites  on  the  edges  of  the  inclined  primary  or  paleozoic 
rocks  of  the  Appalachians  is  seen  at  4  of  the  section,  fig.  505,  p.  388. 
The  absence  of  fish  with  decidedly  heterocercal  tails  may  afford  an 
argument  against  the  Permian  age  of  the  formation  ;  and  the  opinion 
that  the  red  sandstone  is  triassic,  seems,  on  the  whole,  the  best  that  we 
can  embrace  in  the  present  state  of  our  knowledge. 

*  Journal  of  Voyage  of  Beagle,  Ac.  2d  edition,  p.  89,  1845. 


350  DIVISION  OP  THE  PERMIAN   GROUP.        \Ga.  XXIII 

CHAPTER  XXIII. 

PERMIAN    OR   MAGNESIAN    LIMESTONE    GROUP. 

Fossils  of  Magnesian  Limestone  and  Lower  New  Red  distinct  from  the  Triassic— 
Term  Permian — English  and  German  equivalents — Marine  shells  and  corals  of 
English  Magnesian  limestone — Palaeoniscus  and  other  fish  of  the  marl  slate — 
Thecodont  Sauriansof  dolomitic  conglomerate  of  Bristol — Zechstein  and  Rothlie- 
gendes  of  Thuringia — Permian  Flora — Its  generic  affinity  to  the  carboniferous 
— Psaronites  or  tree-ferns. 

WHEN  the  use  of  the  term  "  Poikilitic"  was  explained  in  the  last 
chapter,  I  stated,  that  in  some  parts  of  England  it  is  scarcely  possible  to 
separate  the  red  marls  and  sandstones  so  called  (originally  named  "  the 
New  Red"),  into  two  distinct  geological  systems.  Nevertheless,  the 
progress  of  investigation,  and  a  careful  comparison  of  English  rocks  be- 
tween the  lias  and  the  coal  with  those  occupying  a  similar  geological 
position  in  Germany  and  Russia,  have  enabled  geologists  to  divide  the 
Poikilitic  formation  ;  and  has  even  shown  that  the  lowermost  of  the  two 
divisions  is  more  closely  connected,  by  its  fossil  remains,  with  the  car- 
boniferous group  than  with  the  trias.  If,  therefore,  we  are  to  draw  a 
line  between  the  secondary  and  primary  fossiliferous  strata,  as  between 
the  tertiary  and  secondary,  it  must  run  through  the  middle  of  what  was 
once  called  the  "  New  Red,"  or  Poikilitic  group.  The  inferior  half  of 
this  group  will  rank  as  Primary  or  Paleozoic,  while  its  upper  member 
will  form  the  base  of  the  Secondary  series.  For  the  Lower,  or  Magne- 
sian Limestone  division  of  English  geologists,  Sir  R.  Murchison  proposed, 
in  1841,  the  name  of  Permian,  from  Perm,  a  Russian  government  where 
these  strata  are  more  extensively  developed  than  elsewhere,  occupying  an 
area  twice  the  size  of  France,  and  containing  an  abundant  and  varied 
suite  of  fossils. 

Prof.  King,  in  his  valuable  monograph*  of  the  Permian  fossils  of  Eng- 
land, has  given  a  table  of  the  following  six  members  of  the  Permian 
system  of  the  north  of  England,  with  what  he  conceives  to  be  the  corre- 
sponding formations  in  Thuringia. 

North  of  England.  Thuringia. 

1.  Crystalline  or  concretionary,  and         1.  Stinkstein. 

non-crystalline  limestone. 

2.  Brecciated  and  pseudo-brecciated         2.  Rauchwacke. 

limestone. 

3.  Fossiliferous  limestone.  3.  Dolomit,  or  Upper  Zechstein. 

4.  Compact  limestone.  4,  Zechstein,  or  Lower  Zechstein. 

6.  Marl-slate.  5.  Mergel-schiefer,  or  Kupferschiefer, 

6.  Inferior  sandstones  of  various  col-        6.  Rothliegendes. 
ors. 

*  Palseontographical  Society,  1850,- London. 


CH.  XXIII.]  PERMIAN  LIMESTONES.  351 

I  shall  proceed,  therefore,  to  treat  briefly  of  these  subdivisions,  begin- 
ning with  the  highest,  and  referring  the  reader,  for  a  fuller  description  of 
the  lithological  character  of  the  whole  group,  as  it  occurs  in  the  north 
of  England,  to  a  valuable  memoir  by  Professor  Sedgwick,  published  in 
1835.* 

Crystalline  or  concretionary  limestone  (No.  1). — This  formation  is  seen 
upon  the  coast  of  Durham  and  Yorkshire,  between  the  Wear  and  the 
Tees.  Among  its  characteristic  fossils  are  Schizodus  Schlotheimi  (fig, 
444)  and  Mytilus  septifer  (fig.  446). 

Fig.  444.  Fig.  445.  Fig.  446. 


ScMzodn s  Schlotheimi,  Geinitz.  The  hinge  of  Schizodua  Mytttu*  septifer,  King. 

Crystalline  limestone,  Permian.  truncatus,  King.  Syn.  Modiola  acuminata. 

Permian.  James  Sow. 

Permian  crystalline  lime- 
stone. 

These  shells  occur  at  Hartlepool  and  Sunderland,  where  the  rock  as- 
sumes an  oolitic  and  botroidal  character.  Some  of  the  beds  in  this 
division  are  ripple-marked  ;  and  Mr.  King  imagines  that  the  absence  of 
corals  and  the  character  of  the  shells  indicate  shallow  water.  In  some 
parts  of  the  coast  of  Durham,  where  the  rock  is  not  crystalline,  it  con- 
tains as  much  as  forty-four  per  cent,  of  carbonate  of  magnesia,  mixed 
with  carbonate  of  lime.  In  other  places, — for  it  is  extremely  variable  in 
structure, — it  consists  chiefly  of  carbonate  of  lime,  and  has  concreted 
into  globular  and  hemispherical  masses,  varying  from  the  size  of  a  mar- 
ble to  that  of  a  cannon-ball,  and  radiating  from  the  centre.  '  Occasionally 
earthy  and  pulverulent  beds  pass  into  compact  limestone  or  hard  granu- 
lar dolomite.  The  stratification  is  very  irregular,  in  some  places  well- 
defined,  in  others  obliterated  by  the  concretionary  action  which  has  re- 
arranged the  materials  of  the  rocks  subsequently  to  their  original 
deposition.  Examples  of  this  are  seen  at  Pontefract  and  Eipon  in 
Yorkshire. 

The  brecciated  limestone  (No.  2)  contains  no  fragments  of  foreign 
rocks,  but  seems  composed  of  the  breaking-up  of  the  Permian  limestone 
itself,  about  the  time  of  its  consolidation.  Some  of  the  angular  masses 
in  Tynemouth  Cliff  are  2  feet  in  diameter.  This  breccia  is  considered 
by  Professor  Sedgwick  as  one  of  the  forms  of  the  preceding  limestone, 
No.  1,  rather  than  as  regularly  underlying  it.  The  fragments  are  angu- 
lar and  never  water-worn,  and  appear  to  have  been  re-cemented  on  the 
spot  where  they  were  formed.  It  is,  therefore,  suggested  that  they  may 
have  been  due  to  those  internal  movements  of  the  mass  which  produced 
the  concretionary  structure ;  but  the  subject  is  very  obscure,  and  after 

*  Trans.  Geol.  Soc.  Lond.  Second  Series,  vol.  iii.  p.  37. 


352 


PERMIAN  COMPACT  LIMESTONES. 


[Cfi.  XXIII. 


studying  the  phenomenon  in  the  Marston  Rocks,  on  the  coast  of  Durham, 
I  found  it  impossible  to  form  any  positive  opinion  on  the  subject.  The 
well-known  brecciated  limestones  of  the  Pyrenees  appeared  to  me  to 
present  the  nearest  analogy,  but  on  a  much  smaller  scale. 

The  fossiliferous  limestone  (No.  3)  is  regarded  by  Mr.  King  as  a  deep- 
water  formation,  from  the  numerous  delicate  bryozoa  which  it  includes. 
One  of  these,  Fenestella  retiformis  (fig.  447),  is  a  very  variable  species,  and 

Fig.  447. 

I 


a.  Fenestella  retiformis,  Schlot.  sp. 
Syn.  Gorgonia  infundibuliformis,  Goldf. :  Reteporajlustracea,  Phillips. 

&.  Part  of  the  same  highly  magnified. 
Magnesian  limestone,  Humbleton  Hill,  near  Sunderland.*  "    $ 

has  received  many  different  names.  It  sometimes  attains  a  large  size,  measur- 
ing 8  inches  in  width.  The  same  zoophyte,  or  rather  mollusk,  with  several 
other  British  species,  is  also  found  abundantly  in  the  Permian  of  Germany. 
Shells  of  the  genera  Productus  (fig.  448)  and  Strophalosia  (the  latter 
an  allied  form  with  teeth  in  the  hinge),  which  do  not  occur  in  strata  newer 
than  the  Permian,  are  abundant  in  this  division  of  the  series  in  the  ordinary 

Fig.  448.  Fig.  449. 


Productus  horridus,  Sowerby 
(including  P.  catous,  Sow.) 
Sunderland  and  Durham,  in  Magnesian 
Limestone;    Zechstein  and  Kupfer- 
schiefer,  Germany. 


Spirifer  undulatus,  Sow.  Min.  Con. 
Syn.  Triogonotreta  undulata,  King's 

Monogr.    • 
Magnesiau  Limestone. 


yellow  magnesian  limestone.  They  are  accompanied  by  certain  species  of 
Spirifer  (fig.  449),  and  other  brachiopoda  of  the  true  primary  or  paleozoic 
type.  Some  of  this  same  tribe  of  shells,  such  as  Athyris  Roissyi,  allied  to 
Terebratula,  are  specifically  the  same  as  fossils  of  the  carboniferous  rocks. 
Avicula,  Area,  and  Schizodus  (see  above,  figs.  444%  445,  446),  and  other 
lamellibranchiate  bivalves,  are  abundant,  but  spiral  univalves  are  very  rare. 
The  compact  limestone  (No.  4)  also  contains  organic  remains,  especially 
bryozoa,  and  is  intimately  connected  with  the  preceding.  Beneath  it 
lies  the  marl-slate  (No.  5),  which  consists  of  hard,  calcareous  shales, 
marl-slate,  and  thin-bedded  limestones.  At  East  Thickley,  in  Durham, 
where  it  is  thirty  feet  thick,  this  slate  has  yielded  many  fine  specimens 
*  King's  Monograph,  pi.  2. 


CH.  XXIII.]      FOSSIL   FISH   OF    PERMIAN  MARL-SLATE. 


353 


of  fossil  fish  of  the  genera  Palceoniscus,  Pygopterus,  Coelacanthus,  and 
Platysomus,  genera  which  are  all  found  in  the  coal-measures  of  the  car- 
boniferous epoch,  and  which,  therefore,  says  Mr.  King,  probably  lived  at 
no  great  distance  from  the  shore.  But  the  Permian  species  are  peculiar, 
and,  for  the  most  part,  identical  with  those  found  in  the  marl-slate  or 
copper-slate  of  Thuringia. 

Fig.  450. 


Bestorcd  outline  of  a  fish  of  the  genus  Palceontecus,  Agass. 
Palceothrtesum,  Blainville. 


The  Palceoniscus  above  mentioned  belongs  to  that  division  of  fishes 
which  M.  Agassiz  has  called  "  Heterocercal,"  which  have  their  tails  une- 
qually bilobate,  like  the  recent  shark  and  sturgeon,  and  the  vertebral 
column  running  along  the  upper  caudal  lobe.  (See  fig.  451.)  The 
"  Homocercal"  fish,  which  comprise  almost  all  the  8000  species  at  present 


Fig.  451. 


Fig.  452. 


Shad,  (dupea,  Herring  tribe.) 
Homocercal. 


known  in  the  living  creation,  have  the  tail-fin  either  single  or  equally 
divided ;  and  the  vertebral  column  stops  short,  and  is  not  prolonged 
into  either  lobe.  (See  fig.  451.) 

Now  it  is  a  singular  fact,  first  pointed  out  by  Agassiz,  that  the  heter- 
ocercal  form,  which  is  confined  to  a  small  number  of  genera  in  the  exist- 
ing creation,  is  universal  in  the  Magnesian  limestone,  and  all  the  more 
ancient  formations.  It  characterizes  the  earlier  periods  of  the  earth's 
history,  when  the  organization  of  fishes  made  a  greater  approach  to  that 
of  saurian  reptiles  than  at  later  epochs.  In  all  the  strata  abore  the 
Magnesian  limestone  the  homocercal  tail  predominates. 

A  full  description  has  been  given  by  Sir  Philip  Egerton  of  the  species 
of  fish  characteristic  of  the  marl-slate  in  Prof.  King's  monograph  before 
referred  to,  where  figures  of  the  ichthyolites  which  are  very  entire  and 
well  preserved,  will  be  found.  Even  a  single  scale  is  usually  so  charac- 
teristically marked  as  to  indicate  the  genus,  and  sometimes  even  the  par- 

23 


354 


DOLOMITIC  CONaLOMEKATE. 


[On.  XXIII 


ticular  species.     They  are  often  scattered  through  the  beds  singly,  and 
may  be  useful  to  a  geologist  in  determining  the  age  of  the  rock. 


Fig.  453. 


Scales  of  fish.    Maguesian  limestone. 
Fig.  451  Fig.  455. 


Fig.  456. 


Fig.  453.  PalcEoniseus  comptus,  Agassiz.    Scale  magnified.    Marl-slate. 

Fig.  454.  Palceoniscus  elegans,  Sedg.    Under  surface  of  scale  magnified.    Marl-slate. 

Fig.  455.  Palceoniscus  glaphyrus,  Ag.     Under  surface  of  scale  magnified.    Marl-slate. 

Fig.  456.  Goelacanthus  granulatus,  Ag.    Granulated  surface  of  scale  magnified.    Marl-slate. 


Fig.  45T. 


Fig.  458. 


Pygopterus  mandibularis,  Ag.    Marl-slate. 
a.  Outside  of  scale  magnified. 
&.  Under  surface  of  same. 


Acrolepis  Sedgwickii,  Ag. 

Outside  of  scale  magnified. 
Marl-slate. 


The  inferior  sandstones  (No.  6,  Tab.  p.  350),  which  lie  beneath  the 
marl-slate,  consist  of  sandstone  and  sand,  separating  the  magnesian 
limestone  from  the  coal,  in  Yorkshire  and  Durham.  In  some  instances, 
red  marl  and  gypsum  have  been  found  associated  with  these  beds. 
They  have  been  classed  with  the  magnesian  limestone  'by  Professor 
Sedgwick,  as  being  nearly  co-extensive  with  it  in  geographical  range, 
though  their  relations  are  very  obscure.  In  some  regions  we  find  it 
stated  that  the  imbedded  plants  are  all  specifically  identical  with  those 
of  the  carboniferous  series ;  and,  if  so,  they  probably  belong  to  that 
epoch ;  for  the  true  Permian  flora  appears,  from  the  researches  of 
MM.  Murchison  and  de  Verneuil  in  Eussia,  and  of  Colonel  von  Gutbier 
in  Saxony,  to  be,  with  few  exceptions,  distinct  from  that  of  the  coal  (see 
p.  356). 

Dolomitic  conglomerate  of  Bristol. — Near  Bristol,  in  Somersetshire, 
and  in  other  counties  bordering  the  Severn,  the  unconformable  beds  of 
the  Lower  New  Red,  resting  immediately  upon  the  Coal-measures, 
consist  of  a  conglomerate  called  "dolomitic,"  because  the  pebbles  of 
older  rocks  are  cemented  together  by  a  red  or  yellow  base  of  dolomite 
or  magnesian  limestone.  This  conglomerate  or  breccia,  for  the  im- 
bedded fragments  are  sometimes  angular,  occurs  in  patches  over  the 
whole  of  the  downs  near  Bristol,  filling  up  the  hollows  and  irregulari- 
ties in  the  mountain  limestone,  and  being  principally  composed  at  every 


CH.  XXIIL]  THECODONT   SAURIANS.  355 

spot  of  the  debris  of  those  rocks  on  which  it  immediately  rests.  At 
one  point  we  find  pieces  of  coal-shale,  in  another  of  mountain  lime- 
stone, recognizable  by  its  peculiar  shells  and  zoophites.  Fractured  bones, 
also,  and  teeth  of  saurians,  are  dispersed  through  some  parts  of  the 
breccia. 

These  saurians  (which  until  the  discovery  of  the  Archegosaurus 
in  the  coal  were  the  most  ancient  examples  of  fossil  reptiles)  are  all 
distinguished  by  having  the  teeth  implanted  deeply  in  the  jaw-bone, 
and  in  distinct  sockets,  instead  of  being  soldered,  as  in  frogs,  to  a  simple 
alveolar  parapet.  In  the  dolomitic  conglomerate  near  Bristol,  the  re- 
mains of  species  of  two  genera  have  been  found,  called  Thecodontosaurus 
and  Palceosaurus  by  Dr.  Biley  and  Mr.  Stutchbury  ;*  the  teeth  of  which 
are  conical,  compressed,  and  with  finely  serrated  edges  (figs.  459  and 
460). 

Teeth  of  Saurians,    Dolomitic  conglomerate ;  Redland,  near  Bristol 
Fig.  459.  460. 


Tooth  of  Palaeosaurus  TO  Tooth  of  Thecodontosaurus. 

platyodon,  nat  size.  TR  3  times  magnified. 


Sir  Henry  de  la  Beche  has  shown  that,  in  consequence  of  the  isolated 
position  of  the  breccia  containing  these  fossils,  it  is  very  difficult  to  de- 
termine to  what  precise  part  of  the  Poikilitic  series  they  belong.f  Some 
observers  suspect  them  to  be  triassic ;  but,  until  the  evidence  in  support 
of  that  view  is  more  conclusive,  we  may  continue  to  hold  the  opinion  of 
their  original  discoverers. 

In  Russia,  also,  Thecodont  saurians  of  several  genera  occur,  in  beds  of 
the  Permian  age ;  while  others,  named  P rotor osaur us,  are  met  with  in 
the  Zechstein  of  Thuringia.  This  family  of  reptiles  is  allied  to  the  living 
monitor,  and  its  appearance  in  a  primary  or  paleozoic  formation,  observes 
Prof.  Owen,  is  opposed  to  the  doctrine  of  the  progressive  development  of 
reptiles  from  fish,  or  from  simpler  to  more  complex  forms ;  for,  if  they 
existed  at  the  present  day,  these  monitors  would  take  rank  at  the  head  of 
the  Lacertian  order.J 

We  learn  from  the  writings  of  Sir  R.  Murchison,§  that  in  Russia 
the  Permian  rocks  are  composed  of  white  limestone,  with  gypsum  and 
white  salt ;  and  of  red  and  green  grits,  occasionally  with  copper  ore  ;  also 
magnesian  limestones,  marlstones,  and  conglomerates. 

*  Geol.  Trans.,  Second  Series,  vol.  v.  p.  349,  pi.  29,  figures  2  and  5. 

f  Memoirs  of  Geol.  Survey  of  Great  Britain,  vol.  i.  p.  268. 

j  Owen,  Eeport  on  Reptiles,  British  Assoc.,  Eleventh  Meeting,  1841,  p.  197. 

§  Russia  and  the  Ural  Mountains,  1845 ;  and  Siluria,  ch.  xii.  1854. 


356  PERMIAN  FLOEA.  [Co.  XXIII 

The  country  of  Mansfeld,  in  Thuringia,  may  be  called  the  classic 
ground  of  the  Lower  New  Ked,  or  Magnesian  Limestone,  or  Permian 
formation,  on  the  Continent.  It  consists  there  principally  of,  first,  the 
Zechstein,  corresponding  to  the  upper  portion  of  our  English  series  ;  and, 
secondly,  the  marl-slate,  with  fish  of  species  identical  with  those  of  the 
bed  so  called  in  Durham.  This  slaty  marlstone  is  richly  impregnated 
with  copper-pyrites,  for  which  it  is  extensively  worked.  Magnesian  lime- 
stone, gypsum,  and  rock-salt  occur  among  the  superior  strata  of  this 
group.  At  its  base  lies  the  Rothliegendes,  supposed  to  correspond  with 
the  Inferior  or  Lower  New  Red  Sandstone  above  mentioned,  which  occu- 
pies a  similar  place  in  England  between  the  marl-slate  and  coal.  Its 
local  name  of  "  Rothliegendes,"  red-Iyer,  or  "  Roth-todt-liegendes,"  rcd- 
dead-lyer,  was  given  by  the  workmen  in  the  German  mines  from  its  red 
color,  and  because  the  copper  has  died  out  when  they  reach  this  rock, 
which  is  not  metalliferous.  It  is,  in  fact,  a  great  deposit  of  red  sand- 
stone and  conglomerate,  with  associated  porphyry,  basaltic  trap,  and 
amygdaloid. 

Permian  Flora. — We  learn  from  the  recent  investigation  of  Colonel 
von  Gutbier,  that  in  the  Permian  rocks  of  Saxony  no  less  than  sixty 
species  of  fossil  plants  have  been  met  with,  forty  of  which  have  not  yet 

Fig.  461. 


Walchia piniformis,  Sternb.    Permian,  Saxony.    (Gutbier,  pi.  x.) 
a.  Branch.        &.  Twig  of  the  same.        c.  Leaf  magnified. 

been  found  elsewhere.     Two  or  three  of  .these,  as  Calamites  gigas,  Sphe- 
nopteris  erosa,  and  S.  lobata,  are  also  met  with  in  the  government  oi 
Perm  in  Russia.     Seven  others,  and  among  them  Neuropteris      p    4g2 
Loshii,  Pecopteris  arborescens,  and  P.  similis,  with  several 
species  of  Walchia  (see  fig.  461),  a  genus  of  Conifers,  called 
Lycopodites   by  some   authors,  are  common   to   the  coal- 
measures. 

Among  the  genera  also  enumerated  by  Colonel  Gutbier  are 
the  fruit  called  Cardiocarpon  (see  fig.  462),  Asterophyllites, 
and  Annularia,  so  characteristic  of  the  carboniferous  period  ; 
also  Lepidodendron,  which  is  common  to  the  Permian  of  °ny< 
Saxony,  Thuringia,  and  Russia,  although  not  abundant.     Noeggerathia 


Cn.  XXIII] 


PERMIAN   FLORA. 


357 


Fig.  463. 


(see  fig.  463),  supposed  by  A.  Brongniart  to  be  allied  to  Cycas,  is  another 

link  between  the  Permian  and  Carboniferous  vegetation.     Coniferse,  of 

the  Araucarian  division,  also  occur ;  but  these  are 

likewise  met  with  both  in  older  and  newer  rocks. 

The  plants  called  Sigillaria  and  Stigmaria,  so 

marked  a  feature  in  the  carboniferous  period,  are 

as  yet  wanting. 

Among  the  remarkable  fossils  of  the  rothlie- 
gendes,  or  lowest  part  of  the  Permian  in  Saxony 
and  Bohemia,  are  the  silicified  trunks  of  tree-ferns 
called  generically  Psaronius.  Their  bark  was 
surrounded  by  a  dense  mass  of  air-roots,  which 
often  constituted  a  great  edition  to  the  original 
stem,  so  as  to  double  or  quadruple  its  diameter. 
The  same  remark  holds  good  in  regard  to  certain 
living  extra-tropical  arborescent  ferns,  particularly 
those  of  New  Zealand. 

Psaronites  are  also  found  in  the  uppermost  coal 
of  Autun  in  France,  and  in  the  upper  coal-meas- 
ures of  the  State  of  Ohio  in  the  United  States,  but 
specifically  different  from  those  of  the  rothlie- 
gendes.  They  serve  to  connect  the  Permian  flora 
with  the  more  modern  portion  of  the  preceding  or 

carboniferous  group.  Upon  the  whole,  it  is  evident  that  the  Permian 
plants  approach  much  nearer  to  the  carboniferous  flora  than  to  the  tri- 
assic  ;  and  the  same  may  be  said  of  the  Permian  fauna. 

*  Murchison's  Russia,  voL  ii.  pi.  A,  fig.  8. 


Noeggerafhia  cuneifolia. 
Ad.  Brongniart.* 


358         '  THE  CARBONIFEROUS  GROUP.  [Cn.  XXIV 


CHAPTER  XXIV. 

THE  COAL,  OR  CARBONIFEROUS  GROUP. 

Carboniferous  strata  in  the  southwest  of  England'— Superposition  of  Coal-measures 
to  Mountain  limestone — Departure  from  this  type  in  North  of  England  and 
Scotland — Carboniferous  series  in  Ireland— Sections  in  South  Wales — Under- 
clays  with  Stigmaria — Carboniferous  Flora — Ferns,  Lepidodendra,  Equisetacese, 
Calamites,  Asterophyllites,  Sigillarise,  Stigmarice — Coniferse — Sternbergia — 
Trigonocarpon — Grade  of  Coniferse  in  the  Vegetable  Kingdom — Absence  ot 
Angiosperms — Coal,  how  formed — Erect  fossil  trees — Parkfield  Colliery — St. 
Etienne  Coal-field — 'Oblique  trees  or  snags — Fossil  forests  in  Nova  Scotia — 
Rain-prints — Purity  of  the  Coal  explained — Time  required  for  the  accumula- 
tion of  the  Coal-measures — Brackish- water  and  marine  strata — Crustaceans  ot 
the  Coal — Origin  of  Clay-iron-stone. 

THE  next  group  which  we  meet  with  in  the  descending  order  is  the 
Carboniferous,  commonly  called  "  The  Coal ;"  because  it  contains  many 
beds  of  that  mineral,  in  a  more  or  less  pure  state,  interstratified  with 
sandstones,  shales,  and  limestones.  The  coal  itself,  even  in  Great  Britain 
and  Belgium,  where  it  is  most  abundant,  constitutes  but  an  insignificant 
portion  of  the  whole  mass.  In  the  north  of  England,  for  example,  the 
thickness  of  the  coal-bearing  strata  has  been  estimated  by  Professor  Phil- 
lips at  3000  feet,  while  the  various  coal-seams,  20  or  30  in  number,  do 
not  in  the  aggregate  exceed  60  feet. 

The  carboniferous  formation  assumes  various  characters  in  different 
parts  even  of  the  British  Islands.  It  usually  comprises  two  very  distinct 
members  ;  1st,  that  usually  called  the  Coal-measures,  of  mixed  freshwater, 
terrestrial,  and  marine  origin,  often  including  seams  of  coal ;  2dly,  that 
named  in  England  the  Mountain  or  Carboniferous  Limestone,  of  purely 
marine  origin,  and  containing  corals,  shells,  and  encrinites. 

In  the  Southwestern  part  of  our  island,  in  Somersetshire  and  South 
Wales,  the  three  divisions  usually  spoken  of  by  English  geologists  are  : 

,    n    -,  (  Strata  of  shale,  sandstone,  and  grit,  with  occasional  seams 

J    I      of  coal,  from  600  to  12,000  feet  thick. 

iA  coarse  quartzose  sandstone  passing  into  a  conglomerate, 
sometimes  used  for  millstones,  with  beds  of  shale ;  usually 
devoid  of  coal ;  occasionally  above  600  feet  thick. 

n    K    %n  (.  A  calcareous  rock  containing  marine  shells  and  corals ;  de- 

limVstone  \     void  of  coal ''  thickness  variable,  sometimes  900  feet. 

The  millstone-grit  may  be  considered  as  one  of  the  coal-sandstones 
of  coarser  texture  than  usual,  with  some  accompanying  shales,  in  which 
coal-plants  are  occasionally  found.  In  the  north  of  England  some  bands 


CH.  XXIV.]  COAL-MEASURES.  359 

of  limestone,  with  pectens,  oysters,  and  other  marine  shells,  occur  in  this 
grit,  just  as  in  the  regular  coal-measures,  and  even  a  few  seams  of  coal. 
I  shall  treat,  therefore,  of  the  whole  group  as  consisting  of  two  divisions 
only,  the  Coal-measures  and  the  Mountain  Limestone.  The  latter  is 
found  in  the  southern  British  coal-fields,  at  the  base  of  the  system,  or 
immediately  in  contact  with  the  subjacent  6ld  Red  Sandstone ;  but  as  we 
proceed  northwards  to  Yorkshire  and  Northumberland  it  begins  to  alter- 
nate with  true  coal-measures,  the  two  deposits  forming  together  a  series 
of  strata  about  1000  feet  in  thickness.  To  this  mixed  formation  succeeds 
the  great  mass  of  genuine  mountain  limestone.*  Farther  north,  in  the 
Fifeshire  coal-field  in  Scotland,  we  observe  a  still  wider  departure  from 
the  type  of  the  south  of  England,  or  a  more  complete  intercalation  of 
dense  masses  of  marine  limestones  with  sandstones  and  shales  contain- 
ing coal. 

In  Ireland  a  series  of  shales  and  slates,  constituting  the  base  of  the 
Mountain  Limestone,  attain  so  great  a  thickness,  often  upwards  of  1000 
feet,  as  to  be  classed  as  a  separate  division.  Under  these  slates  is  a  Yel- 
ow  Sands*one,  also  considered  as  carboniferous  from  its  marine  fossils, 
although  passing  into  the  underlying  Devonian.  A  similar  sandstone  of 
much  less  thickness  occurs  in  the  same  position  in  Gloucestershire  and 
South  Wales. 

The  following  are  the  subdivisions  adopted  in  the  geological  map  of 
Ireland,  constructed  by  Mr.  Griffiths : 

Thickness  in  feet 

1.  Coal-measures,  Upper  and  Lower       ....    IQOO  to  2200 

2.  Millstone-grit    -        -        -        -  -        -        -       350  to  1800 

3.  Mountain  limestone,    Upper,  Middle  (or  Calp),  and 

Lower 1200  to  6400 

4.  Carboniferous  slate 700  to  1200 

5.  Yellow  sandstone   (of  Mayo,  <fec.)  with  shales  and 

limestone 400  to  2000 

COAL-MEASURES. 

In  South  Wales  the  coal-measures  have  been  ascertained  by  actual 
measurement  to  attain  the  extraordinary  thickness  of  12,000  feet ;  the 
beds  throughout,  with  the  exception  of  the  coal  itself,  appearing  to  have 
been  formed  in  water  of  moderate  depth,  during  a  slow,  but  perhaps 
intermittent,  depression  of  the  ground,  in  a  region  to  which  rivers  were 
bringing  a  never-failing  supply  of  muddy  sediment  and  sand.  The  same 
area  was  sometimes  covered  with  vast  forests,  such  as  we  see  in  the  deltas 
of  great -rivers  in  warm  climates,  which  are  liable  to  be  submerged  be- 
neath fresh  or  salt  water  should  the  ground  sink  vertically  a  few  feet 

In  one  section  near  Swansea,  in  South  Wales,  where  the  total  thick- 
ness of  strata  is  3246  feet,  we  learn  from  Sir  H.  De  la  Beche  that  there 
are  ten  principal  masses  of  sandstone.  One  of  these  is  500  feet  thick, 

*  Sedgwick,  Geol.  Trans.,  Second  Series,  vol.  iv.;  and  Phillips,  GeoL  of  Yorsh. 
part  2. 


CARBONIFEROUS  FLOKA.  [Ca.  XXIV. 

and  the  whole  of  them  make  together  a  thickness  of  2125  feet.  They 
are  separated  by  masses  of  shale,  varying  in  thickness  from  10  to  50  feet. 
The  intercalated  coal-beds,  sixteen  in  number,  are  generally  from  1  to  5 
feet  thick,  one  of  them,  which  has  two  or  three  layers  of  clay  interposed, 
attaining  9  feet.*  At  other  points  in  the  same  coal-field  the  shales  pre- 
dominate over  the  sandstones.  The  horizontal  extent  of  some  seams  of 
coal  is  much  greater  than  that  of  others,  but  they  all  present  one  charac- 
teristic feature,  in  having,  each  of  them,  what  is  called  its  underclay. 
These  underclays,  coextensive  with  every  layer  of  coal,  consist  of  arena- 
ceous shale,  sometimes  called  fire-stone,  because  it  can  be  made  into  bricks 
which  stand  the  fire  of  a  furnace.  They  vary  in  thickness  from  6  inches 
to  more  than  10  feet ;  and  Mr.  Logan  first  announced  to  the  scientific 
world  in  1841  that  they  were  regarded  by  the  colliers  in  South  Wales  as 
an  essential  accompaniment  of  each  of  the  one  hundred  seams  of  coal 
met  with  in  their  coal-field.  They  are  said  to  form  the  floor  on  which 
the  coal  rests ;  and  some  of  them  have  a  slight  admixture  of  carbonaceous 
matter,  while  others  are  quite  blackened  by  it. 

All  of  them,  as  Mr.  Logan  pointed  out,  are  characterized  by  inclosing  a 
peculiar  species  of  fossil  vegetable  called  Stigmaria,  to  the  exclusion  of 
other  plants.  It  was  also  observed  that,  while  in  the  overlying  shales  or 
"  roof"  of  the  coal,  ferns  and  trunks  of  trees  abound  without  any  Stig- 
marice,  and  are  flattened  and  compressed,  those  singular  plants  of  the 
underclay  very  often  retain  their  natural  forms,  branching  freely,  and 
sending  out  their  slender  leaf-like  rootlets,  formerly  thought  to  be  leaves, 
through  the  mud  in  all  directions.  Several  species  of  Stigmaria  had  long 
been  known  to  botanists,  and  described  by  them,  before  their  position 
under  each  seam  of  coal  was  pointed  out,  and  before  their  true  nature  as 
the  roots  of  trees  was  recognized.  It  was  conjectured  that  they  might 
be  aquatic,  perhaps  floating  plants,  which  sometimes  extended  their 
branches  and  leaves  freely  in  fluid  mud,  and  which  were  finally  enveloped 
in  the  same  mud. 

CARBONIFEROUS   FLORA. 

These  statements  will  suffice  to  convince  the  reader  that  we  cannot 
arrive  at  a  satisfactory  theory  of  the  origin  of  coal  until  we  understand  the 
true  nature  of  Stigmaria  ;  and  in  order  to  explain  what  is  now  known  of 
this  plant,  and  of  others  which  have  contributed  by  their  decay  to  pro- 
duce coal,  it  will  be  necessary  to  offer  a  brief  preliminary  sketch  of  the 
whole  carboniferous  flora,  an  assemblage  of  fossil  plants  with  which  we 
are  better  acquainted  than  with  any  other  which  flourished  antecedently 
to  the  tertiary  epoch.  It  should  also  be  remarked  that  Goppert  has  ascer- 
tained that  the  remains  of  every  family  of  plants  scattered  through  the 
coal-measures  are  sometimes  met  with  in  the  pure  coal  itself,  a  fact  which 
adds  greatly  to  the  geological  interest  attached  to  this  flora. 

Ferns. — The  number  of  species  of  carboniferous  plants  hitherto  de- 
scribed amounts,  according  to  M.  Ad.  Brongniart,  to  about  500.  These 
*  Memoirs  of  Geol.  Survey,  vol.  i.  p.  1-J5. 


CH.  XXIV.]  FERNS  OF  CARBONIFEROUS  PERIOD. 


361 


may  perhaps  be  a  fragment  only  of  the  entire  flora,  but  they  are  enough 
to  show  that  the  state  of  the  vegetable  world  was  then  extremely  different 
from  that  now  prevailing.  We  are  struck  at  the  first  glance  with  the 
similarity  of  many  of  the  ferns  to  those  now  living,  and  the  dissimilarity 


Fig.  464 


Fig.  465. 


Pecopteris  lonchitica. 
(Foss.  Flo.  153.) 


a.  SpTienopteris  crenata. 
&.  Part  of  the  same,  magnified. 
(Fosa.  Flo.  101.) 


Fig.  466. 


of  almost  all  the  other  fossils  except  the  co- 
niferae.  Among  the  ferns,  as  in  the  case  of 
Pecopteris  for  example  (fig.  464),  it  is  not 
always  easy  to  decide  whether  they  should 
be  referred  to  different  genera  from  those 
established  for  the  classification  of  living 
species ;  whereas,  in  regard  to  most  of  the 
other  contemporary  tribes,  with  the  excep- 
tion of  the  coniferse,  it  is  often  difficult  to 
guess  the  family,  or  even  the  class,  to  which 
they  belong.  The  ferns  of  the  carboniferous 
period  are  generally  without  organs  of  fruc- 
tification, but  in  some  specimens  these  are 
well  preserved.  In  the  general  absence  of 
such  characters,  they  have  been  divided  into 
genera  distinguished  chiefly  by  the  branching 
of  the  fronds,  and  the  way  in  which  the  veins  of  the  leaves  are  disposed. 
The  larger  portion  are  supposed  to  have  been  of  the  size  of  ordinary  Eu- 
ropean ferns,  but  some  were  decidedly  arborescent,  especially  the  group 


Caulopteris  primwca,  Lindley. 


362  FERNS — LEPIDODENDRON.  [Cii.  XXIV, 

called  Caulopteris,  by  Lindley,  and  the  Psaronius  of  the  upper  or  newest 
coal  measures,  before  alluded  to  (p.  357). 

All  the  recent  tree-ferns  belong  to  one  tribe  (Polypodiacece\  and  to  ? 
small  number  only  of  genera  in  that  tribe,  in  which  the  surface  of  the 
trunk  is  marked  with  scars,  or  cicatrices,  left  after  the  fall  of  the  fronds. 
These  scars  resemble  those  of  Caulopteris  (see  fig.  466).  No  less  than 
250  ferns  have  already  been  obtained  from  the  coal-strata ;  and,  even  if 
we  make  some  reduction  on  the  ground  of  varieties  which  have  been  mis- 
taken, in  the  absence  of  their  fructification,  for  species,  still  the  result  is 
singular,  because  the  whole  of  Europe  affords  at  present  no  more  than  60 
Indigenous  species. 

Fig.  468. 


Living  tree-ferns  of  different  genera.    (Ad.  Brong.) 
Fig.  467.    Tree-fern  from  Isle  of  Bourbon. 
Fig.  468.     Cyathea  glauca,  Mauritius. 
Fig.  469.    Tree-fern  from  Brazil. 

Lepidodendron. — About  40  species  of  fossil  plants  of  the  Coal  have 
been  referred  to  this  genus.  They  consist  of  cylindrical  stems  or  trunks, 
covered  with  leaf-scars.  In  their  mode  of  branching,  they  are  always  di- 
chotomous  (see  fig.  471).  They  are  considered  by  Brongniart  and  Hooker 
to  belong  to  the  Lycopodiacece,  plants  of  this  family  bearing  cones,  with 
similar  sporangia  and  spores  (fig.  474).  Most  of  them  grew  to  the  size 
of  large  trees.  The  figures  470-472  represent  a  fossil  Lepidodendron,  49 
feet  long,  found  in  Jarrow  Colliery,  near  Newcastle,  lying  in  shale  parallel 
to  the  planes  of  stratification.  Fragments  of  others,  found  in  the  same 
shale,  indicate,  by  the  size  of  the  rhomboidal  scars  which  cover  them,  a 
still  greater  magnitude.  The  living  club-mosses,  of  which  there  are  about 
200  species,  are  abundant  in  tropical  climates,  where  one  species  is  some- 
times met  with  attaining  a  height  of  3  feet.  They  usually  creep  on  the 
ground,  but  some  stand  erect,  as  the  L.  densum,  from  New  Zealand 
(fig.  473). 


LEPIDODENDRON. 

Fig.  4T1. 


363 


Lepidodendron  Sternbergii,    Coal-measures,  near  Newcastle. 

Fig.  4TO.  Branching  trunk,  49  feet  long,  supposed  to  have  belonged  to  L.  Stern- 

lergii.    (Foss.  Flo.  203.) 

Fig.  471.  Branching  stem  with  bark  and  leaves  of  L.  Sternbergii.    (Foss.  Flo.  4) 
Fig.  472.  Portion  of  same  nearer  the  root;  natural  size.    (Ibid.) 


Fig.  473. 


a.  Lycopodium  densum  ;  banks  of  E.  Thames,  New  Zealand. 
6.  Branch,  natural  sue.  c.  Part  of  same  magnified. 

In  the  carboniferous  strata  of  Coalbrook  Dale,  and  in  many  other  coal 
fields,  elongated  cylindrical  bodies,  called  fossil  cones,  named  Lepidostro 
bus  by  M.  Adolphe  Brongniart,  are  met  with.  (See  fig.  474.)  They 
often  form  the  nucleus  of  concretionary  balls  of  clay-ironstone,  and  are 

Fig.  474 


a.  Lepidoitrdbus  ornatvA,  Brong.    Shropshire ;  half  natural  size. 

&.  Portion  of  a  section  showing  the  large  sporangia  in  their  natural  position,  and  each 

supported  by  its  bract  or  scale. 
c.  Spores  in  these  sporangia,  highly  magnified.   (Hooker,  Mem.  Geol.  Survey,  vol.  it  part 

2,  p.  440.) 

well  preserved,  exhibiting  a  conical  axis,  around  which  a  great  quantity 
of  scales  were  compactly  imbricated.  The  opinion  of  M.  Brongniart  is 
now  generally  adopted,  that  the  Lepidostrobus  is  the  fruit  of  Lepidoden- 


364: 


EQUISETACE^ — CALAMITES. 


[On.  XXIV. 


dron  ;  indeed,  it  is  not  uncommon  in  Coalbrook  Dale,  and  elsewhere,  to 
find  these  strobili  or  fruits  terminating  the  tip  of  a  branch  of  a  well  char 
acterized  Lepidodendron. 

Equisetacece. — To  this  family  belong  two  fossil  species  of  the  Coal  • 
one  called  Equisetum  infundibuliforme  by  Brongniart,  and  found  also  in 
jSTova  Scotia,  which  has  sheaths,  regularly  toothed,  ribbed,  and  overlap- 
ping like  those  on  the  young  fertile  stems  of  Equisetum  fluviatile.  It 
was  much  larger  than  any  living  "Horsetail."  The  Equise turn  giganteum, 
discovered  by  Humboldt  and  Bonpland  in  South  America,  attained  a 
height  of  about  5  feet,  the  stern  being  an  inch  in  diameter ;  but  more 
recently  Gardner  has  met  with  one  in  Brazil  15  feet  high,  and  Meyen 
gives  the  height  of  E.  Bogotense  in  Chili  as  15  to  20  feet. 

Calamites. — The  fossil  plants,  so  called,  were  originally  classed  by 
most  botanists  as  cryptogamous,  being  regarded  as  gigantic  Equiseta  ; 


Fig.  4T5. 


Fig.  476. 


Calamites  cannoeformis,  Schlot 
(Foss.  Flo.  79.)  Common  in 
English  coal. 


Calamites  Suckowii,  Brong. ; 
natural  size.  Common  in 
coal  throughout  Europe. 


Fig.  477. 


for,  like  the  common  "  horsetail,"  they  usually  exhibit 
little  more  than  hollow  jointed  stems,  furrowed  ex- 
ternally. (See  figs.  475,  476,  477.) 

Mr.  Salter  stated  to  me,  many  years  ago,  his  con- 
viction that  the  calamite,  as  frequently  represented 
by  paleontologists,  was  in  an  inverted  position,  and 
that  the  conical  part  given  as  the  top  of  the  stem  was 
in  truth  the  root.  This  point  Mr.  Dawson  and  I  had 
opportunities  of  testing  in  Nova  Scotia,  where  we  saw 
many  erect  calamites,  having  their  radical  termination 
as  in  the  annexed  figure  (fig.  477).  The  scars,  from 
which  whorls  of  vessels  have  proceeded,  are  observed 
at  the  upper,  not  the  lower  end  of  each  joint  or  inter- 
node.*  The  specimen,  fig.  475,  therefore,  is  no  doubt 
the  lower  end  of  the  plant,  and  I  have  therefore  re- 
versed its  position  as  given  in  the  work  of  Lindley 
and  Hutton. 

M.  Adolphe  Brongniart,  following  up  the  discoveries  of  Germar  and 
Corda,  has  shown  in  his  "  Genres  de  Vegetaux  Fossiles,"  1849,  that  many 

*  See  Dawson,  Geol.  Quart.  Journal,  1854,  vol.  x.  p.  35. 


Eadical  termination  of 
Scotia. 


CH.  XXIV.] 


CALAMITES. 


365 


Fig.  478. 


Calamites  cannot  belong  to  the  Equiseta,  nor  probably  to  any  tribe  of 
flowerless  plants.  He  conceives  that  they  are  more  nearly  allied  to  the 
Gymnospennous  Dycotyledons.  They  possessed  a  central  pith,  surround- 
ed by  a  ligneous  cylinder,  which  was  divided  by  regular  medullary  rays. 
This  cylinder  was  surrounded  in  turn  by  a  thick  bark.  Of  fossil  stems 
having  this  structure  Brongniart  formed  his  genus  Calamodendron,  which 
includes  many  species  referred  by  Cotta,  Petzholdt,  and  Unger,  to  the 
genus  Calamitea.  The  Calamodendron  is  described  as  smooth  exter- 
nally, its  pith  being  articulated  and  marked  with  deep  external  vertical 
stria?,  agreeing,  in  short,  with  what  geologists  commonly  call  a  Calamite. 
Since  the  appearance  of  Brongniart's  essay,  Mr.  E.  W.  Binney  has  made 
many  important  discoveries  on  the  same  subject ;  and  Mr.  J.  S.  Dawes 
has  published  (Quart.  Journ.  Geol.  Soc.  Lond.  1851,  vol.  vii.  p.  196)  a 

more  complete  account  of  this  sin- 
gular fossil.  Their  views  have  been 
confirmed  by  Prof.  Williamson  of 
Manchester,  who  has  communicated 
to  me  a  specimen,  figured  in  the 
annexed  cut  (fig.  478),  in  which 
we  see  an  internal  pith  answering 
in  character  to  the  Calamodendron, 
and  yet  having  outside  of  it  another 
jointed  cylinder  vertically  grooved 
on  its  outer  surface,  so  that  in  the 
same  stem  we  have  one  calamite 
enveloping  another.  Yet  that  they 
both  formed  part  of  the  same  plant, 
is  proved  by  the  following  circum- 
stances : — 1st.  Near  each  articula- 
tion of  the  pith,  radiating  spokes 

Portion  of  a  Calamite,  near  the  base,  showing  the  -.         A 

external  cylinder,  connected  by  radiating  vessels  ^6  seen   tO    proceed  ana  penetrate 

^to&ft^SS^'™****  ligneous  zone.     One  complete 

Communicated  by  ProtW.C.  Williamson.     ^^    Qr    circ]e   Qf    foesQ    ra(jjj    js 

visible  in  the  annexed  figure  near  the  bottom  of  the  hollow  cavity,  whilst 
another  and  superior  whorl  is  incomplete ;  several  radii,  corresponding 
to  the  first,  remaining,  while  the  rest  have  been  broken  away,  their  place 
being  shown  by  scars  which  they  have  left.  2dly.  In  addition  to  these 
whorls,  called  medullary  by  Prof.  Williamson,  there  are  seen  in  other 
specimens  a  set  of  true  or  ordinary  medullary  rays.  3dly.  The  woody 
zone,  penetrated  both  by  the  spoke-like  vessels  beforementioned  and  by 
the  medullary  rays,  is  usually  reduced  to  brown  carbonaceous  matter, 
preserving  merely  a  tendency  to  break  in  longitudinal  slips,  but  in  some 
specimens  its  fibrous  tissue  is  retained,  and  resembles  that  of  Dadoxylon. 
4thly.  Outside  of  this  zone  again  is  another  cylinder,  supposed  to  have 
been  originally  a  thick  cellular  bark,  nearly  equal  to  one-third  of  the 
whole  stem  in  diameter,  grooved  and  jointed  externally  like  the  pith. 


366  ASTEKOPHYLLITES — SIGILLAKIA.  [On.  XXIV. 

In  conclusion,  I  may  remark,  that  these  discoveries  make  it  more  and 
more  doubtful  to  what  family  the  greater  number  of  Calamites  should  be 
referred.  Their  internal  organization,  says  Prof.  Williamson,  was  very 
peculiar;  for,  while  they  exhibit  remarkable  affinities  with  gymno- 
spermous  dicotyledons,  the  arrangement  of  their  tissues  differs  widely  from 
that  of  all  known  forms  of  gymnosperms. 

Asterophyllites. — The  graceful  plant  represented  in  the  annexed  figure, 
is  supposed  by  M.  Brongniart  to  be  a  branch  of  the  Calamodendron, 
and  he  infers  from  its  pith  and  medullary  rays  that  it  was  dicotyledonous. 
It  appears  to  have  been  allied,  by  the  nature  of  its  tissue,  to  the  gym- 
Fig.  479. 


AsterophylUtesfoliosa.    (Foss.  Flo.  25.)    Coal-measures,  Newcastle. 

nogens,  and  to  Sigillaria.  But  under  the  head  of  Asterophyllites  many 
vegetable  fragments  have  been  grouped  which  probably  belong  to  differ- 
ent genera.  They  have,  in  short,  no  character  in  common,  except  that 
of  possessing  narrow,  verticillate,  one-ribbed  leaves.  Dr.  ISTewberry,  of 
Ohio,  has  discovered  in  the  coal  of  that  country  fossil  stems  which  in 
their  upper  part  bear  wedge-shaped  leaves  corresponding  to  Spheno- 
phyllum,  while  below  the  leaves  are  stalk-like  and  capillary,  and  would 
have  been  called  Asterophyllites  if  found  detached.  From  this  he  infers 
that  Sphenophyllum  was  an  aquatic  plant,  the  superior  and  floating 
leaves  of  which  were  broad,  and  possessed  a  compound  nervation,  while 
the  inferior  or  submersed  leaves  were  linear  and  one-ribbed.  "  This 
supposition,"  he  adds,  "  is  further  strengthened  by  the  extreme  length 
and  tenuity  of  the  branches  of  this  apparently  herbaceous  plant,  which 
would. seem  to  have  required  the  support  of  a  denser  medium  than  air."* 
Sigillaria. — A  large  portion  of  the  trees  of  the  carboniferous  period 
belonged  to  this  genus,  of  which  about  thirty-five  species  are  known. 
The  structure,  both  internal  and  external,  was  very  peculiar,  and,  with 
reference  to  existing  types,  very  anomalous.  They  were  formerly  refer- 
red, by  M.  Ad.  Brongniart,  to  ferns,  which  they  resemble  in  the  scala- 
riform  texture  of  their  vessels,  and,  in  some  degree,  in  the  form  of  the 

*  Annals  of  Science,  Cleveland,  Ohio,  1853,  p.  97. 


Cn.  XXIV.] 


SIGILLARIA  AND   STIGMARIA. 


367 


cicatrices  left  by  the  base  of  the  leaf-stalks  which  have  fallen  off  (see 
fig.  480).  But  with* these  points  of  analogy  to  cryptogamia,  they  corn- 
Fig.  480.  Dme  an  internal  organization  much  resembling 
that  of  Sycads,  and  some  of  them  are  ascer- 
tained to  have  had  long  linear  leaves,  quite 
unlike  those  of  ferns.  They  grow  to  a  great 
height,  from  30  to  60,  or  even  70  feet,  with 
regular  cylindrical  stems,  and  without  branch- 
es, although  some  species  were  dichotomous 
towards  the  top.  Their  fluted  trunks,  from  1 
to  5  feet  in  diameter,  appear  to  have  decayed 
more  rapidly  in  the  interior  than  externally, 
so  that  they  became  hollow  when  standing ; 
and  when  thrown  prostrate  on  the  mud,  they 
were  squeezed  down  and  flattened.  Hence 
we  find  the  bark  of  the  two  opposite  sides  (now 
converted  into  bright  shining  coal)  to  consti- 
tute two  horizontal  layers,  one  upon  the  other, 
half  an  inch,  or  an  inch,  in  thickness.  These  same  trunks,  when  they  are 
placed  obliquely  or  vertically  to  the  planes  of  stratification,  retain  their 
original  rounded  form,  and  are  uncompressed,  the  cylinder  of  bark  having 
been  filled  with  sand,  which  now  affords  a  cast  of  the  interior. 

Dr.  Hooker  still  inclines  to  the  belief  that  the  Sigillarice  may  have 
been  cryptogamous,  though  more  highly  developed  than  any  flowerless 
plants  now  living.  The  scalariform  structure  of  their  vessels  agrees  pre- 
cisely with  that  of  ferns. 

Stigmaria. — This  fossil,  the  importance  of  which  has  already  been 
pointed  out,  was  formerly  conjectured  to  be  an  aquatic  plant.  It  is  now 
ascertained  to  be  the  root  of  Sigillaria.  The  connection  of  the  roots  with 
the  stem,  previously  suspected,  on  botanical  grounds,  by  Brongniart,  was 
first  proved,  by  actual  contact,  in  the  Lancashire  coal-field,  by  Mr. 
Binney.  The  fact  has  lately  been  shown,  even  more  distinctly,  by  Mr. 
Kichard  Brown,  in  his  description  of  the  Stigmarice  occurring  in  the 

Fig.  481. 


Sigillaria  l&vigata,  Brong. 


Stigmaria  attached  to  a  trunk  of  Sigillaria.* 

*  The  trunk  in  this  case  is  referred  by  Mr.  Brown  to  Lepidodendron,  but  his 
illustrations  seem  to  show  the  usual  markings  assumed  by  Sigillaria  near  its 
base. 


368  CONIFERS  OF  THE  COAL   PERIOD.  [On.  XXIV. 

underclays  of  the  coal-seams  of  the  Island  of  Cape  Breton,  in  Nova 
Scotia. 

In  a  specimen  of  one  of  these,  represented  in  the  annexed  figure  (fig. 
481),  the  spread  of  the  roots  was  16  feet,  and  some  of  them  sent  out  root- 
lets, in  all  directions,  into  the  surrounding  clay. 

In  the  sea-cliffs  of  the  South  Joggins  in  Nova  Scotia  I  examined  sev- 
eral erect  Sigtilarias,  in  company  with  Mr.  Dawson,  and  we  found  that 
from  the  lower  extremities  of  the  trunk  they  sent  out  Stigmarice  as  roots. 
All  the  stools  of  the  fossil  trees  dug  out  by  us  divided  into  four  parts,  and 
these  again  bifurcated,  forming  eight  roots,  which  were  also  dichotomous 
when  traceable  far  enough. 

The  manner  of  attachment  of  the  fibres  to  the  stem  resembles  that  of  a 
ball  and  socket  joint,  the  base  of  each  rootlet  being  concave,  and  fitting 
on  to  a  tubercle  (see  figs.  482  and  483).  Rows  of  these  tubercles  are 

Fig.  483. 
Fig.  4821 


Surface  of  another  individual 
of  same  epecies,  showing 
form  of  tubercles.  (Foss. 
Flo.  84.) 


Stigmaria  ficoides,  Brong.  One-fourth  of  nat.  size.  (Foss.  Flo.  32.) 

arranged  spirally  round  each  root,  which  has  always  a  medullary  cavity 
and  woody  texture,  much  resembling  that  of  Sigillaria,  the  structure  of 
the  vessels  being,  like  it,  scalariform. 

Coniferce. — The  coniferous  trees  of  this  period  are  referred  to  five  gen- 
era ;  the  woody  structure  of  some  of  them  showing  that  they  were  allied 
to  the  Araucarian  division  of  pines,  more  than  to  any  of  our  common 
European  firs.  Some  of  their  trunks  exceeded  44  feet  in  height.  Many, 
if  not  all  of  them,  seem  to  have  differed  from  living  Coniferce,  in  having 
large  piths ;  for  Professor  Williamson  has  demonstrated  the  fossil  of  the 
coal-measures  called  Sternlergia  to  be  the  pith  of  these  trees,  or  rather 
the  cast  of  cavities  formed  by  the  sinking  or  partial  absorption  of  the 
original  medullary  axis  (see  figs.  484  and  485).  This  peculiar  type  of 
pith  is  observed  in  living  plants  of  very  different  families,  such  as  the  com- 
mon Walnut  and  the  White  Jasmine,  in  which  the  pith  becomes  so  re- 
duced as  simply  to  form  a  thin  lining  of  the  medullary  cavity,  across 
which  transverse  plates  of  pith  extend  horizontally,  so  as  to  divide  the 
cylindrical  hollow  into  discoid  interspaces.  When  these  last  have  been 
filled  up  with  inorganic  matter,  they  constitute  an  axis  to  which,  before 
their  true  nature  was  known,  the  provisional  name  of  Sterribergia  (d,  d, 
fig.  484)  was  given. 


Cn.  XXIV.]  CONIFERS   OF  THE   COAL   PERIOD. 

Fig.  484 


369 


Fig.  484.  Fragment  of  coniferous  wood,  Dadoxylon, 
Endlicher,  fractured  longitudinally;  from  Coal- 
brook  Dale.  W.  C.  Williamson,* 

a.  Bark. 

6.  Woody  zone  or  fibre  (pleurenchyma). 

c.  Medulla  or  pith. 

d.  Cast  of  hollow  pith,  or  "  Sternhergia." 


Magnified  portion  of  fig.  484;  transverse  section. 
c.  Pith.  Z>,  &.  Woody  fibre.  <?,  e.  Medullary  rays. 

In  the  above  specimen  the  structure  of  the  wood  (6,  figs.  484  and 
485)  is  coniferous,  and  the  fossil  is  referable  to  Endlicher's  fossil  genus 
Dadoxylon. 

The  fossil  named  Trigonocarpon  (figs.  486  and  487),  formerly  supposed 


Fig.  487. 


Fig  486. 


Trigonocarpum  ovatum,  Lindley  &  Hutton. 
Peel  Quarry,  Lancashire. 


Trigonocarpum  olwceforme,  Lindley, 
with  its  fleshy  envelope.  Felling 
Colliery,  Newcastle. 


to  be  the  fruit  of  a  palm,  may  now,  according  to  Dr.  Hooker,  be  referred 
like  the  Sternbergia,  to  the  Coniferce.  Its  geological  importance  is  great, 
for  so  abundant  is  it  in  the  Coal  Measures,  that  in  certain  localities  the 
fruit  of  some  species  may  be  procured  by  the  bushel ;  nor  is  there  any 
nart  of  the  formation  where  they  do  not  occur,  except  the  underclays  and 


*  Manchester  Philos.  Mem.  vol.  ix.  1851. 
24 


370  GRADE   OF   THE   CARBONIFEROUS   FLORA.      [Cn.  XXIV 

limestone.  The  sandstone,  ironstone,  shales,  and  coal  itself,  all  contair 
them.  Mr.  Binney  has  at  length  found  in  the  clay-ironstone  of  Lanca- 
shire several  specimens  displaying  structure,  and  from  these,  says  Dr, 
Hooker,  \ve  learn  that  the  Trigonocarpon  belonged  to  that  large  section 
of  existing  coniferous  plants  which  bear  fleshy  solitary  fruits,  and  not 
cones.  It  resembled  very  closely  the  fruit  of  the  Chinese  genus  Salisburia, 
one  of  the  Yew  tribe,  or  Taxoid  conifers.  In  five  of  the  fossil  specimens 
there  is  evidence  of  four  distinct  integuments,  and  of  a  large  internal 
cavity  filled  with  carbonate  of  lime  and  magnesia,  and  probably  once 
occupied  by  the  albumen  and  embryo  of  the  seed.  The  general  form  of 
the  fossil  when  perfect  is  an  elongated  ovoid,  rather  larger  than  a  hazle- 
tmt.  The  exterior  integument  is  very  thick  and  cellular,  and  was  no 
doubt  once  fleshy  (see  fig.  487).  It  alone  is  produced  beyond  the  seed, 
and  forms  the  beak.  The  second  coat  was  thinner,  but  hard,  and  marked 
by  three  ridges.  This  coat,  being  all  that  commonly  remains  in  a  fossil 
state,  has  suggested  the  name  of  Trigonocarpon.  "Within  this  were  the 
third  and  fourth  coats,  both  of  which  are  very  delicate  membranes,  and 
may  possibly  have  been  two  plates  belonging  to  one  membrane. 

Grade  of  the  Carboniferous  Flora. — On  the  whole,  these  fruits,  says 
Dr.  Hooker,  are  referable  to  "  a  highly  developed  type,  exhibiting  exten- 
sive modifications  of  elementary  organs  for  the  purpose  of  their  adaptation 
to  special  functions,  and  these  modifications  are  as  great,  and  the  adapta- 
tion as  special,  as  any  to  be  found  amongst  analogous  fruits  in  the  ex- 
isting vegetable  world."*  Professor  Williamson,  in  his  paper  on  Stern- 
lergia,  has  likewise  remarked  that  its  structure  was  complex,  and  that 
"  at  a  period  so  early  as  the  carboniferous  all  the  now-existing  forms  of 
vegetable  tissue  appear  to  have  been  created."  These  observations  de- 
serve notice,  because  a  question  has  arisen — whether  the  Coniferce  hold 
a  high  or  a  low  position  among  flowering  plants, — a  point  bearing 
directly  on  the  theory  of  progressive  development.  By  some  botanists 
all  the  Gymnospermous  Dicotyledons  are  regarded  as  inferior  in  grade 
to  .the  Angiosperms.  Others  hold,  with  Dr.  Hooker,  that  the  Gymno- 
sperms  are  not  inferior  in  rank,  having  every  typical  character  of  the 
dicotyledons  highly  developed.  Thus  Coniferse  have  flowers,  and  are 
propagated  by  seeds  which  are  developed  through  the  mutual  action  of 
the  stamens  and  ovules  ;  they  have  distinct  embryos,  and  germinate  in  a 
definite  manner.  The  seed-vessel  (or  ovary)  is  not  closed,  but  this  is  also 
the  case  in  some  genera  of  angiosperms,  in  which  the  ovary  is  open 
before  or  after  impregnation,  so  that  this  character  cannot  be  relied  on 
as  constituting  a  fundamental  difference  in  structural  development.  The 
Coniferae  are  exogenous,  and  have  the  same  distinctions  of  pith,  wood, 
bark,  and  medullary  rays  as  have  the  angiospermous  trees.  Whether 
the  woody  fibre  with  disks  characteristic  of  Coniferse  be  a  more  or  a 
less  complex  tissue  than  the  spiral  vessels,  is  a  controverted  point.  As 
•he  spiral  vessels  occur  in  the  young  shoots,  and  are  lost  in  the  mature 

*  Proceedings  of  the  Royal  Society,  vol.  vii.  March,  1854,  p.  28. 


CH.  XXIV.]   GEADE  OF  THE  CARBONIFEROUS  FLORA.       371 

growth  of  some  plants,  and  as  they  appear  in  many  acrogens,  they  do 
not  seem  to  mark  a  high  development.  In  fine,  there  is  much  ambi- 
guity in  deciding  what  should  or'  should  not  be  called  high  or  low  in 
vegetable  structure,  and  physiologists  entertain  very  different  abstract 
ideas  as  to  the  perfection  of  certain  organs  and  their  relative  func- 
tional importance,  even  where  the  function  is  clearly  ascertained.  It  is 
enough  for  the  geologist  to  know,  that  fossil  Coniferse  abound  in  the 
oldest  rocks  yielding  a  considerable  number  of  vegetable  remains,  and 
that  plants  of  this  order  lay  claim,  if  not  to  the  highest,  at  least  to  so 
high  a  place  in  the  scale  of  vegetable  life,  as  to  preclude  us  from  char- 
acterizing the  carboniferous  flora  as  consisting  of  imperfectly  developed 
plants. 

Although  our  data  are  confessedly  too  defective  to  entitle  us  to  gen- 
eralize respecting  the  entire  vegetable  creation  of  this  era,  yet  we  may 
affirm  that  so  far  as  it  is  known  it  differed  widely  from  any  flora  now 
existing.  The  comparative  rarity  of  Monocotyledons  and  of  Dicotyle- 
donous Angiosperms  seems  clear,  and  the  abundance  of  Ferns  and  Lyco- 
pods  may  justify  Adolphe  Brongniart  in  calling  the  primary  periods  the 
age  of  Acrogens.*  ("  Le  regne  des  Acrogens.")  As  to  the  Sigillariae 
and  Calamites,  they  seem  to  have  been  distinct  from  all  tribes  of  now- 
existing  plants.  That  the  abundance  of  ferns  implies  a  moist  atmo- 
sphere, is  admitted  by  all  botanists ;  but  no  safe  conclusion,  says  Hooker, 
can  be  drawn  from  the  Coniferse  alone,  as  they  are  found  in  hot  and 
dry  and  in  cold  and  dry  climates,  in  hot  and  moist  and  in  cold  and 
moist  regions.  »In  New  Zealand  the  Coniferae  attain  their  maximum  in 
numbers,  constituting  -g^d  part  of  all  the  flowering  plants ;  whereas 
in  a  wide  district  around  the  Cape  of  Good  Hope  they  do  not  form 
j-^o  oth  of  the  phenogamic  flora.  Besides  the  conifers,  many  species  of 
ferns  flourish  in  New  Zealand,  some  of  them  arborescent,  together  with 
many  lycopodiums  ;  so  that  a  forest  in  that  country  may  make  a  nearer 
approach  to  the  carboniferous  vegetation  than  any  other  now  existing  on 
the  globe. 

Angiosperms.  —  Some    of   the    grass-like   leaves  Fig.  488. 

termed  Poacites,  having  fine  longitudinal  striae,  are 
conjectured  to  belong  to  Monocotyledons;  but  the 
determination  is  doubtful,  as  some  of  them  may  be 
the  leaves  of  Lepidodvndra,  others  the  stems  of 
Ferns.  The  curious  plants  called  Antholithes  by 
Lindley  have  usually  been  considered  to  be  flower- 
spikes,  having  what  seems  a  calyx  and  linear  petals 
(see  fig.  488).  But  Dr.  Hooker  suggests  that  these 
may  be  rather  tufts  of  scarcely  opened  buds  with  the 
young  leaves  just  bursting.  He  suggests  that  they 
may  be  coniferous,  although  he  cannot  connect  them 
with  any  known  fossil  conifer. 

*  For  terminology  of  classification  of  plants,  see  above,  note,  p.  265. 


372  COAL — EKECT  FOSSIL  TEEES.  [On.  XXIV. 

Coal,  how  formed — Erect  trees. — I  shall  now  consider  the  manner  in 
which  the  above-mentioned  plants  are  imbedded  in  the  strata,  and  how 
they  may  have  contributed  to  produce  coal.  Professor  Gb'ppert,  after 
examining  the  fossil  vegetables  of  the  coal-fields  of  Germany,  has 
detected,  in  beds  of  pure  coal,  remains  of  plants  of  every  family  hitherto 
known  to  occur  fossil  in  the  coal.  Many  seams,  he  remarks,  are  rich 
in  Sigillarice,  Lepidodendra,  and  Stigmarice,  the  latter  in  such  abun- 
dance, as  to  appear  to  form  the  bulk  of  the  coal.  In  some  places,  almost 
all  the  plants  were  calamities,  in  others  ferns.*  "  Some  of  the  plants  of 
our  coal,"  says  Dr.  Buckland,  "  grew  on  the  identical  banks  of  sand,  silt, 
and  mud,  which,  being  now  indurated  to  stone  and  shale,  form  the  strata 
that  accompany  the  coal ;  whilst  other  portions  of  these  plants  have 
been  drifted  to  various  distances  from  the  swamps,  savannahs,  and  forests 
that  gave  them  birth,  particularly  those  that  are  dispersed  through  the 
sandstones,  or  mixed  with  fishes  in  the  shale  beds."  "At  Balgray,  three 
miles  north  of  Glasgow,"  says  the  same  author,  "  I  saw  in  the  year  1824, 
as  there  still  may  be  seen,  an  unequivocal  example  of  the  stumps  of  sev- 
eral stems  of  large  trees,  standing  close  together  in  their  native  place,  in 
a  quarry  of  sandstone  of  the  coal  formation."! 

Between  the  years  1837  and  1840,  six  fossil  trees  were  discovered  in 
the  coal-field  of  Lancashire,  where  it  is  intersected  by  the  Bolton  rail- 
way. They  were  all  in  a  vertical  position,  with  respect  to  the  plane  of 
the  bed,  which  dips  about  15°  to  the  south.  The  distance  between  the 
first  and  the  last  was  more  than  100  feet,  and  the  roots  of  all  were  im- 
bedded in  a  soft  argillaceous  shale.  In  the  same  plane  with  the  roots 
is  a  bed  of  coal,  eight  or  ten  inches  thick,  which  has  been  ascertained 
to  extend  across  the  railway,  or  to  the  distance  of  at  least  ten  yards. 
Just  above  the  covering  of  the  roots,  yet  beneath  the  coal  seam,  so  large 
a  quantity  of  the  Lepidostrobus  variabilis  was  discovered  inclosed  in  nod- 
ules of  hard  clay,  that  more  than  a  bushel  was  collected  from  the  small 
openings  around  the  base  of  the  trees  (see  figure  of  this  genus,  p.  363). 
The  exterior  trunk  of  each  was  marked  by  a  coating  of  friable  coal,  va- 
rying from  one-quarter  to  three-quarters  of  an  inch  in  thickness  ;  but  it 
crumbled  away  on  removing  the  matrix.  The  dimensions  of  one  of 
the  trees  is  15g  feet  in  circumference  at  the  base,  7£  feet  at  the  top,  its 
height  being  1 1  feet.  All  the  trees  have  large  spreading  roots,  solid 
and  strong,  sometimes  branching,  and  traced  to  a  distance  of  several 
feet,  and  presumed  to  extend  much  farther.  Mr.  Hawkshaw,  who  has 
described  these  fossils,  thinks  that,  although  they  were  hollow  when 
submerged,  they  may  have  consisted  originally  of  hard  wood  through- 
out ;  for  solid  dicotyledonous  trees,  when  prostrated  in  tropical  forests, 
as  in  Venezuela,  on  the  shore  of  the  Caribbean  Sea,  were  observed  by 
him  to  be  destroyed  in  the  interior,  so  that  little  more  is  left  than  an 
outer  shell,  consisting  chiefly  of  the  bark.  This  decay,  he  says,  goes  on 

*  Quart.  Geol.  Journ.,  vol.  v.,  Mem.,  p.  17. 
f  Anniv.  Address  to  Geol.  Soc.,  1840. 


Cu.  XXIV.]  COAL — ERECT  FOSSIL  TREES.  373 

most  rapidly  in  low  and  flat  tracks,  in  which  there  is  a  deep  rich  soil 
and  excessive  moisture,  supporting  tall  forest-trees  and  large  palms,  below 
which  bamboos,  canes,  and  minor  palms  flourish  luxuriantly.  Such  tracts, 
from  their  lowness,  would  be  most  easily  submerged,  and  their  dense  vege- 
tation might  then  give  rise  to  a  seam  of  coal.* 

In  a  deep  valley  near  Capel-Coelbren,  branching  from  the  higher 
part  of  the  Swansea  valley,  four  stems  of  upright  Sigillarice  were  seen, 
in  1838, piercing  through  the  coal-measures  of  S.  Wales;  one  of  them 
was  2  feet  in  diameter,  and  one  13  feet  and  a  half  high,  and  they  were 
all  found  to  terminate  downwards  in  a  bed  of  coal.  "  They  appear/' 
says  Sir  H.  De  la  Beche,  "  to  have  constituted  a  portion  of  a  subterranean 
forest  at  the  epoch  when  the  lower  carboniferous  strata  were  formed."f 

In  a  colliery  near  Newcastle,  say  the  authors  of  the  Fossil  Flora,  a 
great  number  of  Sigillarice  were  placed  in  the  rock  as  if  they  had  re- 
tained the  position  in  which  they  grew.  Not  less  than  thirty,  some  of 
them  4  or  5  feet  in  diameter,  were  visible  within  an  area  of  50  yards 
square,  the  interior  being  sandstone,  and  the  bark  having  been  converted 
into  coal.  The  roots  of  one  individual  were  found  imbedded  in  shale ; 
and  the  trunk,  after  maintaining  a  perpendicular  course  and  circular  form 
for  the  height  of  about  10  feet,  was  then  bent  over  so  as  to  become  hor- 
izontal. Here  it  was  distended  laterally,  and  flattened  so  as  to  be  only 
one  inch  thick,  the  flutings  being  comparatively  distinct  J  Such  vertical 
stems  are  familiar  to  our  miners,  under  the  name  of  coal-pipes.  One  of 
.them,  72  feet  in  length,  was  discovered,  in  1829,  near  Gosforth,  about 
five  miles  from  Newcastle,  in  coal-grit,  the  strata  of  which  it  penetrated. 
The  exterior  of  the  trunk  was  marked  at  intervals  with  knots,  indicating 
the  points  at  which  branches  had  shot  off".  The  wood  of  the  interior 
had  been  converted  into  carbonate  of  lime ;  and  its  structure  was  beau- 
tifully shown  by  cutting  transverse  slices,  so  thin  as  to  be  transparent. 
(See  p.  40.) 

These  "  coal-pipes"  are  much  dreaded  by  our  miners,  for  almost  every 
year  in  the  Bristol,  Newcastle,  and  other  coal-fields,  they  are  the  cause 
of  fatal  accidents.  Each  cylindrical  cast  of  a  tree,  formed  of  solid  sand- 
stone, and  increasing  gradually  in  size  towards  the  base,  and  being  with- 
out branches,  has  its  whole  weight  thrown  downwards,  and  receives  no 
support  from  the  coating  of  friable  coal  which  has  replaced  the  bark. 
As  soon,  therefore,  as  the  cohesion  of  this  external  layer  is  overcome,  the 
heavy  column  falls  suddenly  in  a  perpendicular  or  oblique  direction  from 
the  roof  of  the  gallery  whence  coal  has  been  extracted,  wounding  or  kill- 
ing the  workman  who  stands  below.  It  is  strange  to  reflect  how  many 
thousands  of  these  trees  fell  originally  in  their  native  forests  in  obe- 
dience to  the  law  of  gravity ;  and  how  the  few  which  continued  to  stand 
erect,  obeying,  after  myriads  of  ages,  the  same  force,  are  cast  down  to 
immolate  their  human  victims. 

*  Hawkshaw,  Geol  Trans.,  Second  Series,  voL  vl  pp.  173,  177,  pL  17. 
f  GeoL  Report  on  Cornwall,  Devon,  and  Somerset,  p.  143. 
j  Lindley  and  Hutton,  Foss.  Flo.  part  6,  p.  150. 


374 


PAEKFIELD   COLLIEKY. 


[On.  XXIV 


Fig.  4S9. 


Ground-plan  of  a  fossil  forest,  Parkfield  Colliery,  near 
Wolverhampton,  showing  the  position  of  73  trees  in 
a  quarter  of  an  acre.* 


It  has  been  remarked,  that  if,  instead  of  working  in  the  dark,  the 

miner  was  accustomed  to  remove  the  upper  covering  of  rock  from  each 

seam  of  coal,  and  to  ex- 
pose to  the  day  the  soils 

on  which  ancient  forests 

grew,   the    evidence    of 

their      former     growth 

would  be  obvious.    Thus 

in  South  Staffordshire  a 

seam   of  coal  was   laid 

bare  in  the  year  1844,  in 

what  is  called  an  open 

work   at  Parkfield  Col- 
liery, near  Wolverhamp- 

ton.      In   the   space  of 

about   a   quarter  of  an 

acre  the  stumps  of  no  less 
than  73  trees  with  their 
roots  attached  appeared, 
as  shown  in  the  annexed  plan  (fig.  489),  some  of  them  more  than  8  feet 
in  circumference.  The  trunks  broken  off  close  to  the  root,  were  lying 
prostrate  in  every  direction,  often  crossing  each  other.  One  of  them  meas- 
ured 15,  another  30  feet  in  length,  and  others  less.  They  were  invariably 
flattened  to  the  thickness  of  one  or  two  inches,  and  converted  into  coal. 
Their  roots  formed  part  of  a  stratum  of  coal  10  inches  thick,  which  rested 
on  a  layer  of  clay  2  inches  thick,  below  which  was  a  second  forest,  resting 
on  a  2-foot  seam  of  coal.  Five  feet  below  this  again  was  a  third  forest 
with  large  stumps,  of  Lepidodendra,  Calamites,  and  other  trees. 

In  the  account  given,  in  1821,  by  M.Alex.  Brongniartf  of  the  coal-mine 
of  Treuil,  at  St.  Etienne,  near  Lyons,  he  states,  that  distinct  horizontal  strata 
of  micaceous  sandstone  are  traversed  by  vertical  trunks  of  monocotyledonous 
vegetables,  resembling  bamboos  or  large  Equiseta  (fig.  490).  Since  the  con- 
solidation of  the  stone,  there  has  been  here  and  there  a  sliding  movement, 
which  has  broken  the  continuity  of  the  stems,  throwing  the  upper  parts  of 
them  on  one  side,  so  that  they  are  often  not  continuous  with  the  lower. 

From  these  appearances  it  was  inferred  that  we  have  here  the  monu- 
ments of  a  submerged  forest.  I  formerly  objected  to  this  conclusion, 
suggesting  that,  in  that  case,  all  -  the  roots  ought  to  have  been  found  at 
one  and  the  same  level,  and  not  scattered  irregularly  through  the  mass. 
I  also  imagined  that  the  soil  to  which  the  roots  were  attached  should 
have  been  different  from  the  sandstone  in  which  the  trunks  are  inclosed. 
Having,  however,  seen  calamites  near  Pictou,  in  Nova  Scotia,  buried  at 
various  heights  in  sandstone  and  in  similar  erect  attitudes,  I  have  now 
little  doubt  that  M.  Brongniart's  view  was  correct.  These  plants  seem 
to  have  grown  on  a  sandy  soil,  liable  to  be  flooded  from  time  to  timef 

*  Messrs.  Beckett  and  Ick.     Proceed.  Geol.  Soc.  vol.  iv.  p.  287. 
f  Annales  des  Mines,  1821. 


CH.  XXIV.] 


COAL — ERECT   FOSSIL   TREES. 
Fig.  490. 


375 


Section  showing  the  erect  position  of  fossil  trees  in  coal  sandstone  at 
St  Etienne.    (Alex.  Brongniart) 

and  raised  by  new  accessions  of  sediment,  as  may  happen  in  swamps 
near  the  banks  of  a  large  river  in  its  delta.  Trees  which  delight  in 
marshy  grounds  are  not  injured  by  being  buried  several  feet  deep  at 
their  base ;  and  other  trees  are  continually  rising  up  from  new  soils, 
several  feet  above  the  level  of  the  original  foundation  of  the  morass. 
In  the  banks  of  the  Mississippi,  when  the  water  has  fallen,  I  have  seen 
sections  of  a  similar  deposit  in  which  portions  of  the  stumps  of  trees 
with  their  roots  in  situ  appeared  at  many  different  heights.* 

When  I  visited,  in  1843,  the  quarries  of  Treuil  above-mentioned,  the 
fossil  trees  seen  in  fig.  490  were  removed,  but  I  obtained  proofs  of  other 
forests  of  erect  trees  in  the  same  coal-field. 

Snags. — In  1830,  a  slanting  trunk  was  exposed  in  Craigleith  quarry. 

near  Edinburgh,  the  total  length  of 
which  exceeded  60  feet.  Its  diam- 
eter at  the  top  was  about  7  inches, 
and  near  the  base  it  measured  5 
feet  in  its  greater,  and  2  feet  in  its 
lesser  width.  The  bark  was  con- 
verted into  a  thin  coating  of  the 
purest  and  finest  coal,  forming  a 
striking  contrast  in  color  with  the 
white  quartzose  sandstone  in  which 
it  lay.  The  annexed  figure  repre- 
sents  a  portion  of  this  tree,  about 
to'&E2d7oburgh'  Ansleofinclinationfronia  15  feet  long,  which  I  saw  exposed 


Fig.  491. 


*  Prlhciples  of  Geol.  9th  ed.  p.  268. 


376 


COAL — OBLIQUE   FOSSIL  TKEES. 


[Cn.  XXIV. 


in  1830,  when  all  the  strata  had  been  removed  from  one  side.  The 
beds  which  remained  were  so  unaltered  and  undisturbed  at  the  point  of 
junction,  as  clearly  to  show  that  they  had  been  tranquilly  deposited 
round  the  tree,  and  that  the  tree  had  not  subsequently  pierced  through 
them,  while  they  were  yet  in  a  soft  state.  They  were  composed  chiefly 
of  siliceous  sandstone,  for  the  most  part  white  ;  and 
divided  into  laminae  so  thin,  that  from  six  to  fourteen 
of  them  might  be  reckoned  in  the  thickness  of  an 
inch.  Some  of  these  thin  layers  were  dark,  and 
contained  coaly  matter  ;  but  the  lowest  of  the  in- 
tersected  beds  were  calcareous.  The  tree  could  not 
have  been  hollow  when  imbedded,  for  the  interior 
still  preserved  the  woody  texture  in  a  perfect  state, 
the  petrifying  matter  being,  for  the  most  part,  calca- 
reous.* It  is  also  clear,  that  the  lapidifying  matter 
was  not  introduced  laterally  from  the  strata  through 
which  the  fossil  passes,  as  most  of  these  were  not 
calcareous.  It  is  well  known  that,  in  the  Mississippi 
and  other  great  American  rivers,  where  thousands  of 
trees  float  annually  down  the  stream,  some  sink 
with  their  roots  downwards,  and  become  fixed  in  the 
mud.  Thus  placed,  they  have  been  compared  to  a 
lance  in  rest,  and  so  often  do  they  pierce  through  the 
bows  of  vessels  which  run  against  them,  that  they 
render  the  navigation  extremely  dangerous.  Mr.  Hugh 
Miller  mentions  four  other  huge  trunks  exposed  in 
quarries  near  Edinburgh,  which  lay  diagonally  across 
the  strata  at  an  angle  of  about  30°,  with  their  lower 
or  heavier  portions  do  wnwards,the  roots  of  all,  save  one, 
rubbed  off  by  attrition.  One  of  these  was  60  and  an- 
other  70  feet  in  length,  and  from  4  to  6  feet  in  diameter. 
The  number  of  years  for  which  the  trunks  of  trees, 
when  constantly  submerged,  can  resist  decomposition, 
is  very  great  ;  as  we  might  suppose  from  the  durability 
of  wood,  in  artificial  piles,  permanently  covered  by  water. 
Hence  these  fossil  snags  may  not  imply  a  rapid  accumu- 
lation  of  beds  of  sand,  although  the  channel  of  a  river  or 
part  of  a  lagoon  is  often  filled  up  in  a  very  few  years. 

Nova  Scotia.  —  One  of  the  finest  examples  in  the 
world  of  a  succession  of  fossil  forests  of  the  carboniferous 
period,  laid  open  to  view  in  a  natural  section,  is  that 
seen  in  the  lofty  cliffs,  called  the  South  Joggins,  bor- 
dering  the  Chignecto  Channel,  a  branch  of  the  Bay  of 
Fundy,  in  Nova  Scotia.f 

*  See  figures  of  texture,  "Witbam,  Foss.  Veget.  pi.  3. 
f  See  Lyell's  Travels  in  N.  America,  vol.  ii.  p.  179  ;  and.Dawson,  Geol.  Journ.  No.  87 


* 


CH.  XXIV.]       COAL — FOSSIL   FORESTS   IX   XOVA  SCOTIA.  377 

In  the  annexed  section  (fig.  492),  which  I  examined  in  July,  1842, 
the  beds  from  c  to  i  are  seen  all  dipping  the  same  way,  their  average 
inclination  being  at  an  angle  of  24°  S.  S.  W.  The  vertical  height  of  the 
cliffs  is  from  150  to  200  feet;  and  between  d  and  g,  in  which  space  I 
observed  seventeen  trees  in  an  upright  position,  or,  to  speak  more  cor- 
rectly, at  right  angles  to  the  planes  of  stratification,  I  counted  nineteen 
seams  of  coal,  varying  in  thickness  from  2  inches  to  4  feet.  At  low  tide 
a  fine  horizontal  section  of  the  same  beds  is  exposed  to  view  on  the 
beach.  The  thickness  of  the  beds  alluded  to,  between  d  and  g,  is  about 
2500  feet,  the  erect  trees  consisting  chiefly  of  large  Sigillarice,  occurring 
at  ten  distinct  levels,  one  above  the  other ;  but  Mr.  Logan,  who  after- 
wards made  a  more  detailed  survey  of  the  same  line  of  cliffs,  found  erect 
trees  at  seventeen  levels,  extending  through  a  vertical  thickness  of  4515 
feet  of  strata ;  and  he  estimated  the  total  thickness  of  the  carboniferous 
formation,  with  and  without  coal,  at  no  less  than  14,570  feet,  everywhere 
devoid  of  marine  organic  remains.*  The  usual  height  of  the  buried 
trees  seen  by  me  was  from  6  to  8  feet ;  but  one  trunk  was  about  25  feet 
high  and  4  feet  in  diameter,  with  a  considerable  bulge  at  the  base.  In 
no  instance  could  I  detect  any  trunk  intersecting  a  layer  of  coal,  how- 
ever thin ;  and  most  of  the  trees  terminated  downwards  in  seams  of  coal 
Some  few  only  were  based  in  clay  and  shale ;  none  of  them,  except 
calamites,  in  sandstone.  The  erect  trees,  therefore,  appeared  in  general 
to  have  grown  on  beds  of  coal.  In  the  underclays  Stigmaria  abounds. 

In  1852  Mr.  Dawson  and  the  author  made  a  detailed  examination  of 
one  portion  of  the  strata,  1400  feet  thick,  where  the  coal-seams  are  most 
frequent,  and  found  evidence  of  root-bearing  soils  at  sixty-eight  different 
levels.  Like  the  seams  of  coal  which  often  cover  them,  these  root-beds 
or  old  soils  are  at  present  the  most  destructible  masses  in  the  whole  cliff, 
the  sandstones  and  laminated  shales  being  harder  and  more  capable  of 
resisting  the  action  of  the  waves  and  the  weather.  Originally  the  re- 
verse was  doubtless  true,  for  in  the  existing  delta  of  the  Mississippi  those 
clays  in  which  the  innumerable  roots  of  the  deciduous  cypress  and  other 
swamp  trees  ramify  in  all  directions  are  seen  to  withstand  far  more  effec- 
tually the  undermining  power  of  the  river,  or  of  the  sea  at  the  base  of 
the  delta,  than  do  beds  of  loose  sand  or  layers  of  mud  not  supporting 
trees. 

This  fact  may  explain  why  seams  of  coal  have  so  often  escaped  denu- 
dation, and  remain  continuous  over  wide  areas,  since  the  tough  roots,  now 
turned  to  coal,  which  once  traversed  them,  would  enable  them  to  resist  a 
current  of  water,  whilst  other  members  of  the  coal-formation,  in  their 
original  and  unconsolidated  state  of  sand  and  mud,  would  be  readily  re- 
moved. 

In  regard  to  the  plants,  they  belonged  to  the  same  genera,  and  most 

of  them  to  the  same  species,  as  those  met  with  in  the  distant  coal-fields 

of  Europe.     In  the  sandstone,  which  filled  their  interiors,  I  frequently 

observed  fern-leaves,  and  sometimes  fragments  of  Stigmaria,  which  had 

*  Quart.  GeoL  Journ.  voL  ii.  p.  177. 


378 


COAL — FOSSIL   FOKESTS  IN  NOVA  SCOTIA.       [Cn.  XXIV. 


evidently  entered  together  with  sediment  after  the  trunk  had  decayed  and 
become  hollow,  and  while  it  was  still  standing  under  water.  Thus  the  tree, 
a,  6,  fig.  493,  the  same  which  is  represented  at  a,  fig.  494,  or  in  the  bed  e  in 
the  larger  section,  fig.  492,  is  a  hollow  trunk  5  feet  8  inches  in  length,  tra- 
versing various  strata,  and  cut  off  at  the  top  by  a  layer  of  clay  2  feet  thick 


Fossil  tree  at  right  angles  to  planes  of  stratification. 
Coal  measures,  Nova  Scotia. 

Pig.  494. 


Erect  fossil  trees.    Coal-measures,  Nova  Scotia. 

on  which  rests  a  seam  of  coal  (6,  fig.  494)  1  foot  thick.  On  this  coal 
again  stood  two  large  trees  (c  and  d),  while  at  a  greater  height  the  trees 
/  and  g  rest  upon  a  thin  seam  of  coal  (e),  and  above  them  is  an  under- 
day,  supporting  the  4-foot  coal. 

If  we  now  return  to  the  tree  first  mentioned  (fig.  493),  we  find  the 
diameter  (a  b)  14  inches  at  the  top  and  16  inches  at  the  bottom,  the 
length  of  the  trunk  5  feet  8  inches.  The  strata  in  the  interior  consisted 
of  a  series  entirely  different  from  those  on  the  outside.  The  lowest  of 
the  three  outer  beds  which  it  traversed  consisted  of  purplish  and  blue 
shale  (c,  fig.  493),  2  feet  thick,  above  which  was  sandstone  (d)  1  foot 
thick,  and  above  this  clay  (e)  2  feet  8  inches.  But,  in  the  interior,  were 
nine  distinct  layers  of  different  composition :  at  the  bottom,  first,  shale  4 
inches,  then  sandstone  1  foot,  then  shale  4  inches,  then  sandstone  4  inches, 
then  shale  1 1  inches,  then  clay  (/)  with  nodules  of  ironstone  2  inches, 
then  pure  clay  2  feet,  then  sandstone  3  inches,  and  lastly,  clay  4  inches. 


CH.  XXIV.]      COAL — FOSSIL   FORESTS   OF  NOVA  SCOTIA.  379 

Owing  to  the  outward  slope  of  the  face  of  the  cliff,  the  section  (fig.  493) 
was  not  exactly  perpendicular  to  the  axis  of  the  tree ;  and  hence,  probably, 
the  apparent  sudden  termination  at  the  base  without  a  stump  and  roots. 

In  this  example  the  layers  of  matter  in  the  inside  of  the  tree  are  more 
numerous  than  those  without;  but  it  is  more  common  in  the  coal- 
measures  of  all  countries  to  find  a  cylinder  of  pure  sandstone, — the  cast 
of  the  interior  of  a  tree,  intersecting  a  great  many  alternating  beds  of 
shale  and  sandstone,  which  originally  enveloped  the  trunk  as  it  stood 
erect  in  the  water.  Such  a  want  of  correspondence  in  the  materials 
outside  and  inside,  is  just  what  we  might  expect  if  we  reflect  on  the 
difference  of  time  at  which  the  deposition  of  sediment  will  take  place  in 
the  two  cases ;  the  imbedding  of  the  tree  having  gone  on  for  many 
years  before  its  decay  had  made  much,  progress. 

In  many  places  distinct  proof  is  seen  that  the  enveloping  strata  took 
years  to  accumulate,  for  some  of  the  sandstones  surrounding  erect  sigilla- 
rian  trunks  support  at  different  levels  roots  and  stems  of  Calamites  ;  the 
Calamites  having  begun  to  grow  after  the  older  Sigillarice  had  been  par- 
tially buried. 

The  general  absence  of  structure  in  the  interior  of  the  large  fossil 
trees  of  the  Coal  implies  the  very  durable  nature  of  their  bark,  as 
compared  with  their  woody  portion.  The  same  difference  of  dura- 
bility of  bark  and  wood  exists  in  modern  trees,  and  was 'first  pointed 
out  to  me  by  Mr.  Dawson,  in  the  forests  of  Nova  Scotia,  where  the 
Canoe  Birch  (Betula  papyracea)  has  such  tough  bark  that  it  may 
sometimes  be  seen  in  the  swamps  looking  externally  sound  and  fresh, 
although  consisting  simply  of  a  hollow  cylinder  with  all  the  wood  de- 
cayed and  gone.  In  such  cases  the  submerged  portion  is  sometimes 
found  filled  with  mud. 

One  of  the  erect  fossil  trees  of  the  South  Joggins  has  been  shown  by 
Mr.  Dawson  to  have  Araucarinn  structure,  so  that  some  Coniferce  of  the 
Coal  period  grew  in  the  same  swamps  as  Sigillarice,  just  as  now  the 
deciduous  Cypress  (Taxodium  distichum)  abounds  in  the  marshes  of 
Louisiana,  even  to  the  edge  of  the  sea. 

When  the  carboniferous  forests  sank  below  high-water  mark  a  spe- 
cies of  Spirorbis  or  Serpula  (fig.  498)  attached  itself  to  the  outside 
of  the  stumps  and  stems  of  the  erect  trees,  adhering  occasionally 
even  to  the  interior  of  the  bark, — another  proof  that  the  process  of 
envelopment  was  very  gradual.  These  hollow  upright  trees,  covered 
with  innumerable  marine  annelids,  reminded  me  of  a  "  cane-brake," 
as  it  is  commonly  called,  consisting  of  tall  reeds  of  Arundinaria 
macrosperma,  which  I  saw,  in  1846,  at  the  Balize,  or  extremity  of  the 
delta  of  the  Mississippi.  Although  these  reeds  are  freshwater  plants, 
they  were  covered  with  barnacles,  having  been  killed  by  an  incursion 
of  salt  water  over  an  extent  of  many  acres,  where  the  sea  had  for 
a  season  usurped  a  space  previously  gained  from  it  by  the  river. 
Yet  the  dead  reeds,  in  spite  of  this  change,  remained  standing  in  the 
soft  mud,  showing  how  easily  the  Sigillarice,  hollow  as  they  were 


380  COAL — FOSSIL  FORESTS  OF  NOVA  SCOTIA.       [Cn.  XXIV. 

but  supported  by  strong  roots,  may  have  resisted  an  incursion  of 
the  sea. 

The  high  tides  of  the  Bay  of  Fundy,  rising  more  than  60  feet,  are  so 
destructive  as  to  undermine  and  sweep  away  continually  the  whole  face 
of  the  cliffs,  and  thus  a  new  crop  of  erect  fossil  trees  is  brought  into 
view  eveiy  three  or  four  years.  They  are  known  to  extend  over  a  space 
between  two  or  three  miles  from  north  to  south,  and  more  than  twice 
that  distance  from  east  to  west,  being  seen  in  the  banks  of  streams  inter- 
secting the  coal-field. 

In  Cape  Breton,  Mr.  Richard  Brown  has  observed  in  the  Sydney 
coal-field  a  total  thickness  of  coal-measures,  without  including  the 
underlying  millstone-grit,  of  1843  feet,  dipping  at  an  angle  of  8°. 
He  has  published  minute  details  of  the  whole  series,  showing  at  how 
many  different  levels  erect  trees  occur,  consisting  of  Sigillaria,  Le- 
pidodendron,  Calamites,  and  other  genera.  In  one  place  eight  erect 
trunks,  with  roots  and  rootlets  attached  to  them,  were  seen  at  the 
same  level,  within  a  horizontal  space  80  feet  in  length.  Beds  of  coal 
of  various  thickness  are  interstratified.  Taking  into  account  forty- 
one  clays  filled  with  roots  of  Stigmaria,  in  their  natural  position, 
and  eighteen  layers  of  upright  trees  at  other  levels,  there  is,  on  the 
whole,  clear  evidence  of  at  least  fifty-nine  fossil  forests,  ranged  one 
above  the  other,  in  this  coal-field,  in  the  above-mentioned  thickness 
of  strata.* 

The  fossil  shells  of  Cape  Breton  and  those  of  the  Nova  Scotia  section 
(p.  378)  consisting  of  Cypris,  Unio  (?),  Modiola,  and  an  annelid  proba- 
bly of  the  genus  Spirorbis  (see  fig.  498),  seem  to  indicate  brackish  water; 
but  we  ought  never  to  be  surprised  if,  in  pursuing  the  same  stratum,  we 
should  come  either  to  a  freshwater  or  a  purely  marine  deposit  ;  for  this 
will  depend  upon  our  taking  a  direction  higher  up  or  lower  down  the 
ancient  river  or  delta  deposit. 

In  the  strata  above  described,  the  association  of  clays  supporting  up- 
right trees,  with  other  beds  containing  marine  and  brackish-water  shells, 
implies  such  a  repeated  change  in  the  same  area,  from  land  to  sea  and 
from  sea  to  land,  that  here,  if  anywhere,  we  should  expect  to  meet  with 
evidence  of  the  fall  of  rain  on  ancient  sea-beaches.  Accordingly  rain-prints 
were  seen  by  me  and  Mr.  Dawson  d:  various  levels,  but  the  most  perfect 
hitherto  observed  were  discovered  by  Mr.  Brown  near  Sydney  in  Cape 
Breton.  They  consist  of  very  delicate  impressions  of  rain-drops  on  green- 
ish slates,  with  several  worm-tracks  (a,  &,  fig.  495),  such  as  usually  accom- 
pany rain-marks  on  the  recent  mud  of  the  Bay  of  Fundy,  and  other 
modern  beaches. 

The  casts  of  rain-prints,  in  figs.  496  and  491,  project  from  the  under 
side  of  two  layers,  occurring  at  different  levels,  the  one  a  sandy 
shale,  resting  on  the  green  shale  (fig.  495),  the  other  a  sandstone 
presenting  a  similar  warty  or  blistered  surface,  on  which  are  also 

*  Geol.  Quart.  Journ.  vol.  ii.  p.  393;  and  vol.  vi.  p.  115. 


CH.  XXIV.]  COAL  —  RAIN-PRINTS. 

Fig.  495. 


381 


FK  495.  Carboniferous  rain-prints  with  worm-tracks  (a,  b)  on  green  shale,  from  Cape 

Breton,  Nova  Scotia.    Natural  size. 

Fig.  496.  Casts  of  rain-prints  on  a  portion  of  the  same  slab,  fig.  495,  seen  on  the  under 

side  of  an  incumbent  layer  of  arenaceous  shale.    Natural  #ize. 

The  arrow  represents  the  supposed  direction  of  the  shower. 

observable  some  small  ridges  as   at  a,  which  stand  out  in  relief,  and 
afford  evidence  of  cracks  formed  by  the  shrinkage  of  subjacent  clay,  on 


Fig.  497. 


fig.  497.  Casts  of  carboniferous  rain-prints  and  shrinkage-cracks  (a)  on  the  under 
side  of  a  layer  of  sandstone,  Cape  Breton,  Nova  Scotia.    Natural  size. 

which  rain  had  fallen.     Many  of  the  associated  sandstones  are  ripple- 
marked. 

The  great  humidity  of  the  climate  of  the  coal  period  had  been  pre- 
viously inferred  from  the  nature  of  its  vegetation  and  the  continuity  of 
its  forests  for  hundreds  of  miles ;  but  it  is  satisfactory  to  have  at  length 
obtained  such  positive  proofs  of  showers  of  rain,  the  drops  of  which 
resembled  in  their  average  size  those  which  now  fall  from  the  clouds. 
From  such  data  we  may  presume  that  the  atmosphere  of  the  carbo- 
niferous period  corresponded  in  density  with  that  now  investing  the 
globe,  and  that  different  currents  of  air  varied  then  as  now  in  tempera- 


382  PURITY   OF  THE   COAL.  [On.  XXiV. 

ture,  so  as  to  give  rise,  by  their  mixture,  to  the  condensation  of  aqueous 
vapor. 

The  more  closely  the  strata  productive  of  coal  have  been  studied 
the  greater  has  become  the  force  of  the  evidence  in  favor  of  their 
having  originated  in  the  manner  of  modern  deltas.  They  display  a 
vast  thickness  of  stratified  mud  and  fine  sand  without  pebbles,  and  in 
them  are  seen  countless  stems,  leaves,  and  roots  of  terrestrial  plants,  free 
for  the  most  part  from  all  intermixture  of  marine  remains, — circumstances 
which  imply  the  persistency  in  the  same  region  of  a  vast  body  of  fresh 
water.  This  water  was  also  charged,  like  that  of  a  great  river,  with  an 
inexhaustible  supply  of  sediment,  which  seems  to  have  been  transported 
over  alluvial  plains  so  far  from  the  higher  grounds  that  all  coarser  parti- 
cles and  gravel  were  left  behind.  Such  phenomena  imply  the  drainage 
and  denudation  of  a  continent  or  large  island,  having  within  it  one  or 
more  ranges  of  mountains.  The  partial  intercalation  of  brackish-water 
beds  at  certain  points  is  equally  consistent  with  the  theory  of  a  delta,  the 
lower  parts  of  which  are  always  exposed  to  be  overflowed  by  the  sea  even 
where  no  oscillations  of  level  are  experienced. 

The  purity  of  the  coal  itself,  or  the  absence  in  it  of  earthy  particles 
and  sand,  throughout  areas  of  vast  extent,  is  a  fact  which  appears  very 
difficult  to  explain  when  we  attribute  each  coal-seam  to  a  vegetation 
growing  in  swamps.  It  has  been  asked  how,  during  river  inundations, 
capable  of  sweeping  away  the  leaves  of  ferns  and  the  stems  and  roots  of 
Sigillarice  and  other  trees,  could  the  waters  fail  to  transport  some  fine 
mud  into  the  swamps  ?  One  generation  after  another  of  tall  trees  grew 
with  their  roots  in  mud,  and  their  leaves  and  prostrate  trunks  formed 
layers  of  vegetable  matter,  which  was  afterwards  covered  with  mud  since 
turned  to  shale.  Yet  the  coal  itself  or  altered  vegetable  matter  remained 
all  the  while  unsoiled  by  earthy  particles.  This  enigma,  however  per- 
plexing at  first  sight,  may,  I  think,  be  solved,  by  attending  to  what  is 
now  taking  place  in  deltas.  The  dense  growth  of  reeds  and  herbage 
which  encompasses  the  margins  of  forest-covered  swamps  in  the  valley 
and  delta  of  the  Mississippi  is  such  that  the  fluviatile  waters,  in  passing 
through  them,  are  filtered  and  made  to  clear  themselves  entirely  before 
they  reach  the  areas  in  which  vegetable  matter  may  accumulate  for 
centuries,  forming  coal  if  the  climate  be  favorable.  There  is  no  pos- 
sibility of  the  least  intermixture  of  earthy  matter  in  such  cases. 
Thus  in  the  large  submerged  tract  called  the  "  Sunk  Country,"  near 
New  Madrid,  forming  part  of  the  western  side  of  the  valley  of  the 
Mississippi,  erect  trees  have  been  standing  ever  since  the  year  1811-12, 
killed  by  the  great  earthquake  of  that  date ;  lacustrine  and  swamp 
plants  have  been  growing  there  in  the  shallows,  and  several  rivers 
have  annually  inundated  the  whole  space,  and  yet  have  been  unable  to 
carry  in  any  sediment  within  the  outer  boundaries  of  the  morass,  so 
dense  is  the  marginal  belt  of  reeds  and  brushwood.  It  may  be  affirmed 
that  generally  in  the  "  cypress  swamps"  of  the  Mississippi  no  sediment 
mingles  with  the  vegetable  matter  accumulated  there  from  the  decay  of 


CH.  XXIV.]          LONG  PERIODS  OF  ACCUMULATION.  383 

trees  and  semi-aquatic  plants.  As  a  singular  proof  of  this  fact,  I  may 
mention  that  whenever  any  part  of  a  swamp  in  Louisiana  is  dried  up, 
during  an  unusually  hot  season,  and  the  wood  set  on  fire,  pits  are 
burnt  into  the  ground  many  feet  deep,  or  as  far  down  as  the  fire  can 
descend,  without  meeting  with  water,  and  it  is  then  found  that  scarcely 
any  residuum  or  earthy  matter  is  left.*  At  the  bottom  of  all  these 
"  cypress  swamps"  a  bed  of  clay  is  found,  with  roots  of  the  tall  cypress 
(Taxodium  dtstichum),  just  as  the  underclays  of  the  coal  are  filled  with 
Stigmaria. 

It  has  been  already  stated,  that  the  carboniferous  strata  at  the  South 
Joggins,  in  Nova  Scotia,  are  nearly  three  miles  thick,  and  the  coal- 
njeasures  are  ascertained  to  be  of  vast  thickness  near  Pictou,  more  than 
100  miles  to  the  eastward.  If,  therefore,  we  speculate  on  the  probable 
volume  of  solid  matter,  contained  in  the  Nova  Scotia  coal-fields,  there 
appears  little  danger  of  erring  on  the  side  of  excess  if  ^ye  take  the 
average  thickness  of  the  beds  at  7500  feet,  or  about  half  that  ascertained 
to  exist  in  one  carefully-measured  section.  As  to  the  area  of  the  coal- 
field, it  includes  a  large  part  of  New  Brunswick  to  the  west,  and  extends 
north  to  Prince  Edward's  Island,  and  probably  to  the  Magdalen  Isles. 
When  we  add  the  Cape  Breton  beds,  and  the  connecting  strata,  which 
must  have  been  denuded  or  are  still  concealed  beneath  the  waters  of  the 
Gulf  of  St.  Lawrence,  we  obtain  an  area  comprising  about  36,000  square 
miles.  This,  with  the  thickness  of  7500  feet  before  assumed,  will  give 
51,000  cubic  miles  of  solid  matter  as  the  volume  of  the  carboniferous 
rocks. 

The  Mississippi  would  take  more  than  two  million  of  years  to  convey 
to  the  Gulf  of  Mexico  an  equal  quantity  of  solid  matter  in  the  shape 
of  sediment,  assuming  the  average  discharge  of  water,  in  that  great  river 
to  ba  as  calculated  by  Mr.  Forshey,  450,000  cubic  feet  per  second, 
througnout  the  year,  and  the  total  quantity  of  mud  to  be,  as  estimated  by 
Mr.  Riddell,  3,702,758,400  cubic  feet  in  the  year.f 

The  Ganges,  according  to  the  data  supplied  to  me  by  Mr.  Everest  and 
Captain  Strachey,  conveys  so  much  larger  a  volume  of  solid  matter  an- 
nually to  the  Bay  of  Bengal,  that  it  might  accomplish  a  similar  task  in 
375,000  years,  or  in  less  than  a  fifth  of  the  time  which  the  Mississippi 
would  require.^ 

As  the  lowest  of  the  carboniferous  strata  of  Nova  Scotia,  like  the 
middle  and  uppermost,  consist  of  shallow-water  beds,  the  whole  vertical 
subsidence  of  three  miles,  at  the  South  Joggins,  must  have  taken  place 
gradually.  If  then  this  depression  was  brought  about  in  the  course  of 
375,000  years,  it  did  not  exceed  the  rate  of  four  feet  in  a  century,  resem- 
bling that  now  experienced  in  certain  countries,  where,  whether  the 


*  Lyell's  Second  Visit  to  the  U.  S.,  vol.  ii.  p.  245 ;  and  American  Journ.  of 
Science,  2d  series,  vol.  v.  p.  17. 

f  Principles  of  Geology,  9th  ed.  1853,  p.  273. 
j  Ibid.  1853,  p.  283. 


384:  BRACKISH-WATER  AND   MARINE   STRATA.      [On.  XXIV. 

movement  be  upward  or  downward,  it  is  quite  insensible  to  the  inhabi- 
tants, and  only  known  by  scientific  inquiry.  If,  on  the  other  hand,  it 
was  brought  about  in  two  millions  of  years  according  to  the  other  stan- 
dard before  alluded  to,  the  rate  would  be  only  six  inches  in  a  century. 
But  the  same  movement  taking  place  in  an  upward  direction  would  be 
sufficient  to  uplift  a  portion  of  the  earth's  crust  to  the  height  of  Mont 
Blanc,  or  to  a  vertical  elevation  of  three  miles  above  the  level  of  the  sea, 

The  delta  of  the  Ganges  presents  in  one  respect  a  striking  parallel  to 
the  Nova  Scotia  coal-field,  since  at  Calcutta  at  the  depth  of  eight  or  ten 
feet  from  the  surface  the  buried  stools  of  trees  with  their  roots  attached 
have  been  found  in  digging  tanks,  indicating  an  ancient  soil  now  under- 
ground ;  and,  in  boring  on  the  same  site  for  an  Artesian  well  to  the 
depth  of  481  feet,  other  signs  of  ancient  forest-covered  lands  and  peaty 
soils  have  been  observed  at  several  depths,  even  as  far  down  as  300  feet 
and  more  below  the  level  of  the  sea.  As  the  strata  pierced  through  con- 
tained freshwater  remains  of  recent  species  of  plants  and  animals,  they 
imply  a  subsidence  which  has  been  going  on  contemporaneously  with  the 
accumulation  of  fluviatile  mud. 

In  the  English  coal-fields  the  same  association  of  fresh,  or  rather 
brackish-water  strata,  with  marine,  in  close  connection  with  beds  of  coal 
of  terrestrial  origin,  has  been  frequently  recognized.  Thus,  for  example, 
a  deposit  near  Shrewsbury,  probably  formed  in  brackish  water,  has  been 
described  by  Sir  R.  Murchison  as  the  youngest  member  of  the  carbo- 
niferous series  of  that  district,  at  the  point  where  the  coal-measures  are 
in  contact  with  the  Permian  or  "  Lower  New  Red."  It  consists  of  shales 
and  sandstones  about  150  feet  thick,  with  coal  and  traces  of  plants ; 
including  a  bed  of  limestone,  varying  from  2  to  9  feet  in  thickness,  which 
is  cellular,  and  resembles  some  lacustrine  limestones  of  France  and  Ger 
many.  It  has  been  traced  for  30  miles  in  a  straight  line,  and  can  be 
recognized  at  still  more  distant  points.  The  characteristic  fossils  are  a 
small  bivalve,  having  the  form  of  a  Cyclas  or  Cyrena,  also  a  small  ento- 
mostracan  which  may  be  a  Cyprif,  or,  if  marine,  a  Cythere  (fig.  499), 
and  the  microscopic  shell  of  an  annelid  of  an  extinct  genus  called  Micro- 
conchus  (fig.  498),  allied  to  Serpula  or  Spirorlis. 

Fig.  498.  Fig.  499. 


a.  Microconchus  (Spirorlis)  Cypris  f  inflate  (or  Cythere  f). 

carbonarius.    Nat  size,  Nat.  size,  and  magnified. 

and  magnified.  Murchison,* 

Z>.  var.  of  same. 

*  Silurian  System,  p.  84. 


CH.  XXIV.] 


CKUSTACEANS   OF  THE   COAL. 


385 


Fig.  500. 


In  the  lower  coal-measures  of  Coalbrook  Dale,  the  strata,  accord- 
ing to  Mr.  Prestwich,  often  change  completely  within  very  short  dis- 
tances, beds  of  sandstone  passing  horizontally  into  clay,  and  clay  intc 
sandstone.  The  coal-seams  often  wedge  out  or  disappear  ;  and  sections, 
at  places  nearly  contiguous,  present  marked  lithological  distinctions. 
Tn  this  single  field,  in  which  the  strata  are  from  TOO  to  800  feet  thick, 
between  forty  and  fifty  species  of  terrestrial  plants  have  been  discovered, 
besides  several  fishes  of  the  genera  Megalichthys,  Holoptychius,  and 
others.  Crustacea  also  are  met  with,  of  the 
genus  Limulus  (see  fig.  500),  resembling  in 
all  essential  characters  the  Limuli  of  the 
Oolitic  period,  and  the  king-crab  of  the 
modern  seas.  They  were  smaller,  however, 
than  the  living  form,  and  had  the  abdomen 
deeply  grooved  across,  and  serrated  at  its 
edges.  In  this  specimen,  the  tail  is  wanting ; 
but  in  another,  of  a  second  species,  from 
Coalbrook  Dale,  the  tail  is  seen  to  agree  with  Limulus  rotundatu*,  Prestwich. 

-o       v    .        T.        T  Coal,  Coa.brook  Dale. 

that  ot  the  living  Limulus. 

The  perfect   carapace   of  a   long-tailed   or   decapod   crustacean   ha* 
also  been  found  in  the  iron-stone  of  these  strata  by  Mr.  Ick  (see  fig. 
501).     It  is  referred  by  Mr.  Salter  to  Glyphea,  a  genus  also  occur- 
ring in  the  Lias  and  Oolite.     There  are  also 
upwards  of  forty  species  of  mollusca,  among 
which  are  two  or  three  referred  to  the  fresh- 
water genus    Unio,   and   others   of   marine 
forms,  such  as  Nautilus,  Orthoceras,  Spirifer. 
and  Productus.     Mr.  Prestwich  suggests  that 
the  intermixture  of  beds  containing  freshwater 
shells   with   others   full   of  marine  remains, 
and  the  alternation  of  coarse  sandstone  and 
conglomerate  with  beds  of  fine  clay  or  shale 
containing  the  remains  of  plants,  may  be  ex-         Glyp1ieaf  duMa,  Saltcr. 
plained  by  supposing  the  deposit  of  Coalbrook  Syn.  Apus  duUm,  Milne  Edward?. 

_•'       rr.  The  oldest  recorded   decapod  (or 

Dale  to  have  originated  m  a  bay  of  the  sea  or      long-tailed)  crustacean.     Cosi- 

.    ,        -i-r/i          3  -  j       ri       •  measures,  Coalbrook  Dale. 

estuary  into  which  flowed  a  considerable  river 
subject  to  occasional  freshes.* 

One  or  more  species  of  scorpions,  two  beetles  of  the  family  Curcu- 
lionidce,  and  a  neuropterous  insect  resembling  the  genus  Corydalis,  and 
another  related  to  the  Phasmidce,  have  been  found  at  Coalbrook  Dale. 
From  the  Coal  of  Wetting  in  Westphalia  several  specimens  of  the  cock- 
roach or  Blatta  family,  and  the  wing  of  a  cricket  (Acridites),  have  been 
described  by  Germar.f 


Fig.  501. 


*  Prestwich,  GeoL  Trans.,  2d  series,  voL  v.  p.  440. 
f  See  Munster's  Beitr.  voL  v.  pi.  13,  1842. 
25 


386 


CLAY-IRON-STONE. 


[On.  XXIV 


More  recently  (1854)  Mr.  Fr.  Goldenberg  has  published  descriptions 
of  no  less  than  twelve  species  of  insects  from  the  nodular  clay-iron-stone 
of  Saarbruck  near  Treves.*  They  are  associated  with  the  leaves  and 
branches  of  fossil  ferns.  Among  them  are  several  Blattinci,  three  species 
of  Neuroptera,  one  beetle  of  the  Scarabceus  family,  a  grasshopper  or 
locust,  Gryllacris  (see  fig.  502),  and  several  white  ants  or  Termites. 

Fig.  502. 


Wing  of  a  Grasshopper. 

GryUacris  lithanthraca,  Goldenberg. 

Coal,  Saarbruck  near  Treves. 


These  newly-added  species  probably  outnumber  all  we  knew  before  of 
the  fossil  insects  of  the  coal. 

In  the  Edinburgh  coal-field,  at  Burdiehouse,  fossil  fishes,  mollusks, 
and  cyprides  (?),  very  similar  to  those  in  Shropshire  and  Stafford- 
shire, have  been  found  by  Dr.  Hibbert.  In  the  coal-field  also  of 
Yorkshire  there  are  freshwater  strata,  some  of  which  contain  shells 
referred  to  the  genus  Unio  ;  but  in  the  midst  of  the  series  there  is  one 
thin  but  very  widely-spread  stratum,  abounding  in  fishes  and  marine 
shells,  such  as  Goniatites  Listen  (fig.  503),  Orthoceras,  and  Avicula 
papyracea,  Goldf.  (fig.  504). 


Fig.  503. 


Fig.  &U4. 


Goniatites  Listeri,  Martin,  sp. 


A  vicula  pap yracea,  Goldf. 
(Pecten  papyraceus,  Sow.) 


No  similarly  intercalated  layer  of  marine  shells  has  been  noticed  in 
the  neighboring  coal-field  of  Newcastle,  where,  as  in  South  Wales  and 


*  Palceont.  Bunker  and  V.  Meyer,  vol.  iv.  p.  17. 


CH.  XXV.]  COAL-FIELDS  OF  UNITED  STATES.  387 

Somersetshire,  the  marine  deposits  are  entirely  below  those  containing 
terrestrial  and  freshwater  remains.* 

Clay-iron-stone. — Bands  and  nodules  of  clay-iron-stone  are  common 
in  coal-measures,  and  are  formed,  says  Sir  H.  De  la  Beche,  of  carbonate 
of  iron,  mingled  mechanically  with  earthy  matter,  like  that  constituting 
the  shales.  Mr.  Hunt,  of  the  Museum  of  Practical  Geology,  instituted 
a  series  of  experiments  to  illustrate  the  production  of  this  substance,  and 
found  that  decomposing  vegetable  matter,  such  as  would  be  distributed 
through  all  coal  strata,  prevented  the  farther  oxidation  of  the  proto-salts 
of  iron,  and  converted  the  peroxide  into  protoxide  by  taking  a  portion 
of  its  oxygen  to  form  carbonic  acid.  Such  carbonic  acid,  meeting  with 
the  protoxide  of  iron  in  solution,  would  unite  with  it  and  form  a  car- 
bonate of  iron ;  and  this  mingling  with  fine  mud,  when  the  excess  of 
carbonic  acid  was  removed,  might  form  beds  or  nodules  of  argillaceous 
iron-stone.f 


CHAPTER  XXV. 
CARBONIFEROUS  GROUP — continued, 

Coal-fields  of  the  United  States — Section  of  the  country  between  the  Atlantic 
and  Mississippi — Position  of  land  in  the  carboniferous  period  eastward  of  the 
Alleghanies — Mechanically  formed  rocks  thinning  out  westward,  and  limestones 
thickening — Uniting  of  many  coal-seams  into  one  thick  bed — Horizontal  coal 
at  Brownsville,  Pennsylvania — Vast  extent  and  continuity  of  single  seams  of 
coal — Ancient  river-channel  in  Forest  of  Dean  coal-field — Climate  of  carbo- 
niferous period — Insects  in  coal — Rarity  of  air-breathing  animals — Great  num- 
ber of  fossil  fish — First  discovery  of  the  skeletons  of  fossil  reptiles — Footprints 
of  reptilians — First  land-shell  found — Rarity  of  air-breathers,  whether  verte- 
brate or  invertebrate,  in  Coal-measures — Mountain  limestone— Its  corals  and 
marine  shells. 

IT  was  stated  in  the  last  chapter  that  a  great  uniformity  prevails  in 
the  fossil  plants  of  the  coal-measures  of  Europe  and  North  America ; 
and  I  may  add  that  four-fifths  of  those  collected  in  Nova  Scotia  have 
been  identified  with  European  species.  Hence  the  former  existence  at 
the  remote  period  under  consideration  (the  carboniferous)  of  a  continent 
or  chain  of  islands  where  the  Atlantic  now  rolls  its  waves  seems  a  fair 
inference.  Nor  are  there  wanting  other  and  independent  proofs  of  such 
an  ancient  land  situated  to  the  eastward  of  the  present  Atlantic  coast  of 
North  America ;  for  the  geologist  deduces  the  same  conclusion  from  the 
mineral  composition  of  the  carboniferous  and  some  older  groups  of  rocks 
as  they  are  developed  on  the  eastern  flanks  of  the  Alleghanies,  contrasted 
with  their  character  in  the  low  country  to  the  westward  of  those  moun 
tains. 

The  annexed  diagram  (fig.   505)  will  assist  the  reader  in  under- 

*  Phillips ;  art,  "  Geology,"  Encyc.  Metrop.  p.  592. 
f  Memoirs  of  Geol.  Survey,  pp.  51,  255,  <fec. 


388        GEOLOGICAL  STKUCTUKE   OF  UNITED  STATES.      [On.  XXV 


T-'  <N  cc  -* 


CH.  XXV.]  CARBONIFEROUS  GROUP.  389 

standing  the  phenomena  now  alluded  to,  although  I  must  guard  him 
against  supposing  that  it  is  a  true  section.  A  great  number  of  details 
have  of  necessity  been  omitted,  and  the  scale  of  heights  and  horizontal 
distances  are  unavoidably  falsified. 

Starting  from  the  shores  of  the  Atlantic,  on  the  eastern  side  of  the 
Continent,  we  first  come  to  a  low  region  (A  B),  which  was  called  the 
alluvial  plain  by  the  first  geographers.  It  is  occupied  by  tertiary  and 
cretaceous  strata,  before  described  (pp.  180,  231,  and  254),  which  are 
nearly  horizontal.  The  next  belt,  from  B  to  c,  consists  of  granitic  rocks 
(hypogene),  chiefly  gneiss  and  mica-schist,  covered  occasionally  with 
unconformable  red  sandstone,  No.  4  (New  Red  or  Trias  ?),  remarkable 
for  its  footprints  (see  p.  346).  Sometimes,  also,  this  sandstone  rests 
on  the  edges  of  the  disturbed  paleozoic  rocks  (as  seen  in  the  section). 
The  region  (B  c),  sometimes  called  the  "Atlantic  Slope,"  corresponds 
nearly  in  average  width  with  the  low  and  flat  plain  (A  B),  and  is  charac- 
terized by  hills  of  moderate  height,  contrasting  strongly,  in  their  rounded 
shape  and  altitude,  with  the  long,  steep,  and  lofty  parallel  ridges  of  the 
Alleghany  mountains.  The  out-crop  of  the  strata  in  these  ridges,  like 
the  two  belts  of  hypogene  and  newer  rocks  (A  B,  and  B  c),  above  alluded 
to,  when  laid  down  on  a  geological  map,  exhibit  long  stripes  of  different 
colors,  running  in  a  N.  E.  and  S.  W.  direction,  in  the  same  way  as  the 
lias,  chalk,  and  other  secondary  formations  in  the  middle  and  eastern 
half  of  England. 

The  narrow  and  parallel  zones  of  the  Appalachians  here  mentioned, 
consist  of  strata,  folded  into  a  succession  of  convex  and  concave  flexures, 
subsequently  laid  open  by  denudation.  The  component  rocks  are  of 
great  thickness,  all  referable  to  the  Silurian,  Devonian,  and  Carboniferous 
formations.  There  is  no  principal  or  central  axis,  as  in  the  Pyrenees  and 
many  other  chains — no  nucleus  to  which  all  the  minor  ridges  conform  ; 
but  the  chain  consists  of  many  nearly  equal  and  parallel  foldings,  having 
what  is  termed  an  anticlinal  and  synclinal  arrangement  (see- above,  p.  48). 
This  system  of  hills  extends,  geologically  considered,  from  Vermont  to 
Alabama,  being  more  than  1000  miles  long,  from  50  to  150  miles  broad, 
and  varying  in  height  from  2000  to  6000  feet.  Sometimes  the  whole 
assemblage  of  ridges  runs  perfectly  straight  for  a  distance  of  more  than 
50  miles,  after  which  all  of  them  wheel  round  altogether,  and  take  a  new 
direction,  at  an  angle  of  20  or  30  degrees  to  the  first. 

We  are  indebted  to  the  state  surveyors  of  Virginia  and  Pennsylvania, 
Prof.  W.  B.  Rogers  and  his  brother  Prof.  H.  D.  Rogers,  for  the  import- 
ant discovery  of  a  clue  to  the  general  law  of  structure  prevailing  through- 
out this  range  of  mountains,  which,  however  simple  it  may  appear  when 
once  made  out  and  clearly  explained,  might  long  have  been  overlooked, 
amidst  so  great  a  mass  of  complicated  details.  It  appears  that  the  bend- 
ing and  fracture  of  the  beds  is  greatest  on  the  southeastern  or  Atlantic 
side  of  the  chain,  and  the  strata,  become  less  and  less  disturbed  as  we  go 
westward,  until  at  length  they  regain  their  original  or  horizontal  posi- 
tion. By  reference  to  the  section  (fig.  505),  it  will  be  seen  that  on  the 


390  APPALACHIAN  CHAIN.  [On.  XXV 

eastern  side,  or  in  the  ridges  and  troughs  nearest  the  Atlantic,  south 
eastern  dips  predominate,  in  consequence  of  the  beds  having  been  folded 
back  upon  themselves,  as  in  i,  those  on  the  north  western  side  of  each  arch 
having  been  inverted.  The  next  set  of  arches  (such  as  k)  are  more  open, 
each  having  its  western  side  steepest ;  the  next  (I)  open  out  still  more 
widely,  the  next  (m)  still  more,  and  this  continues  until  we  arrive  at  the 
low  and  level  part  of  the  Appalachian  coal-field  (D  E). 

In  nature  or  in  a  true  section,  the  number  of  bendings  or  parallel 
folds  is  so  much  greater  that  they  could  not  be  expressed  in  a  diagram 
without  confusion.  It  is  also  clear  that  large  quantities  of  rock  have 
been  removed  by  aqueous  action  or  denudation,  as  will  appear  if  we 
attempt  to  complete  all  the  curves  in  the  manner  indicated  by  the  dotted 
lines  at  i  and  k. 

The  movements  which  imparted  so  uniform  an  order  of  arrangement 
to  this  vast  system  of  rocks  must  have  been,  if  not  contemporaneous,  at 
least  parts  of  one  and  the  same  series,  depending  on  some  common  cause. 
Their  geological  date  is  well  defined,  at  least  within  certain  limits,  for 
they  must  have  taken  place  after  the  deposition  of  the  carboniferous 
strata  (No.  5),  and  before  the  formation  of  the  red  sandstone  (No.  4). 
The  greatest  disturbing  and  denuding  forces  have  evidently  been  ex- 
erted on  the  southeastern  side  of  the  chain  ;  and  it  is  here  that  igneous 
or  plutonic  rocks  are  observed  to  have  invaded  the  strata,  forming  dykes, 
some  of  which  run  for  miles  in  lines  parallel  to  the  main  direction  of  the 
Appalachians,  or  N.N.E.  and  S.  S.  W. 

The  thickness  of  the  carboniferous  rocks  in  the  region  c  is  very  great, 
and  diminishes  rapidly  as  we  proceed  to  the  westward.  The  surveys  of 
Pennsylvania  and  Virginia  show  that  the  southeast  was  the  quarter 
whence  the  coarser  materials  of  these  strata  were  derived,  so  that  the  an7 
cient  land  lay  in  that  direction.  The  conglomerate  which  forms  the  gen- 
eral base  of  the  coal-measures  is  1500  feet  thick  in  the  Sharp  Mountain, 
where  I  saw  it  (at  c)  near  Pottsville  ;  whereas  it  has  only  a  thickness  of 
500  feet  about  thirty  miles  to  the  northwest,  and  dwindles  gradually 
away  when  followed  still  farther  in  the  same  direction,  until  its  thickness 
is  reduced  to  30  feet.*  The  limestones,  on  the  other  hand,  of  the  coal- 
measures,  augment  as  we  trace  them  westward.  Similar  observations 
have  been  made  in  regard  to  the  Silurian  and  Devonian  formations  in 
New  York ;  the  sandstones  and  all  the  mechanically-formed  rocks  thin- 
ning out  as  they  go  westward,  and  the  limestones  thickening,  as  it  were, 
at  their  expense.  It  is,  therefore,  clear  that  the  ancient  land  was  to  the 
east,  where  the  Atlantic  now  is  ;  the  deep  sea,  with  its  banks  of  coral 
and  shells  to  the  west,  cr-  where  the  hydrographical  basin  of  the  Missis- 
sippi is  now  situated. 

In  that  region,  near  Pottsville,  where  the  thickness  of  the  coal-meas- 
ures is  greatest,  there  are  thirteen  seams  of  anthracitic  coal,  several  of 
them  more  than  2  yards  tljick.  Some  of  the  lowest  of  these  alternate 

*  H.  D.  Rogers,  Trans.  Assoc.  Amer.  Geol.  1840-42,  p.  440. 


CH.  XXV.] 


UNION  OF  COAL-SEAMS. 


391 


•with  beds  of  white  grit  and  conglomerate  of  coarser  grain  than  I  ever 
saw  elsewhere,  associated  with  pure  coal.  The  pebbles  of  quartz  ar< 
often  of  the  size  of  a  hen's  egg.  On  following  these  pudding-stones  and 
grits  for  several  miles  from  Pottsville,  by  Tamaqua,  to  the  Lehigh  Sum- 
mit Mine,  in  company  with  Mr.  H.  D.  Rogers,  in  1841,  he  pointed  out 
to  me  that  the  coarse-grained  strata  and  their  accompanying  scales 
gradually  thin  out,  until  seven  seams  of  coal,  at  first  widely  separated, 
are  brought  nearer  and  nearer  together,  until  they  successively  unite  ;  so 
that  at  last  they  form  one  mass,  between  40  and  50  feet  thick.  I  saw 
this  enormous  bed  of  anthracite  coal  quarried  in  the  open  air  at  Mauch 
Chunk  (or  the  Bear  Mountain),  the  overlying  sandstone,  40  feet  Jiick, 
having  been  removed  bodily  from  the  top  of  the  hill,  which,  to  use  the 
miner's  expression,  had  been  "  scalped."  The  accumulation  of  vegetable 
matter  now  constituting  this  vast  bed  of  anthracite,  may  perhaps,  before 
it  was  condensed  by  pressure  and  the  discharge  of  its  hydrogen,  oxygen, 
and  other  volatile  ingredients,  have  been  between  200  and  300  feet 
thick.  The  origin  of  such  a  vast  thickness  of  vegetable  remains,  so  un- 
mixed with  earthy  ingredients,  can,  I  think,  be  accounted  for  in  no  other 
way,  than  by  the  growth,  during  thousands  of  years,  of  trees  and  ferns, 
in  the  manner  of  peat, — a  theory  which  the  presence  of  the  Stigmaria 
in  situ  under  each  of  the  seven  layers  of  anthracite,  fully  bears  out. 
The  rival  hypothesis,  of  the  drifting  of  plants  into  a  sea  or  estuary,  leaves 
the  absence  of  sediment,  or,  in  this  case,  of  sand  and  pebbles,  wholly  un- 
explained. 

"But  the  student  will  naturally  ask,  what  can  have  caused  so  many 
seams  of  coal,  after  they  had  been  persistent  for  miles,  to  come  together 
and  blend  into  one  single  seam,  and  that  one  equal,  in  the  aggregate, 
to  the  thickness  of  the  several  separate  seams  ?  Often  had  the  same 
question  been  put  by  English  miners  before  a  satisfactory  answer  was 
given  to  it  by  the  late  Mr.  Bowman.  The  following  is  his  solution  of 
the  problem.  Let  act,',  fig.  506,  be  a  mass  of  vegetable  matter,  capable, 

Fig.  506. 


when  condensed,  of  forming  a  3-foot  seam  of  coal.  It  rests  on  the 
underclay  b  6',  filled  with  roots  of  trees  in  situ,  and  it  supports  a  grow- 
ing forest  (c  D).  Suppose  that  part  of  the  same  forest  D  E  had  become 
submerged  by  the  ground  sinking  down  25  feet,  so  that  the  trees  have 
been  partly  thrown  down  and  partly  remain  erect  in  water,  slowly  de- 


HOKIZONTAL   COAL   STEATA.  [Cn.  XXV. 

faying,  their  stumps  and  tlie  lower  parts  of  their  trunks  being  enveloped 
in  layers  of  sand  and  mud,  which  are  gradually  filling  up  the  lake  DF 
When  this  lake  or  lagoon  has  at  length  been  entirely  silted  up  and 
converted  into  land,  say,  in  the  course  of  a  century,  the  forest  c  D  will 
extend  once  more  continuously  over  the  whole  area  c  F,  as  in  fig.  507, 
and  another  mass  of  vegetable  matter  (g  g'),  forming  3  feet  more  of 
coal,  may  accumulate  from  c  to  F.  We  then  find  in  the  region  F,  two 
seams  of  coal  (af  and  g')  each  3  feet  thick,  and  stparated  by  25  feet  of 
sandstone  and  shale,  with  erect  trees  based  upon  the  lower  coal,  while, 
between  D  and  c,  we  find  these  two  seams  united  into  a  2-yard  coal. 
It  may  be  objected  that  the  uninterrupted  growth  of  plants  during  the 
interval  of  a  century  will  have  caused  the  vegetable  matter  in  the  re- 
gion c  D  to  be  thicker  than  the  two  distinct  seams  a'  and  g'  at  F  ;  and 
no  doubt  there  would  actually  be  a  slight  excess  representing  one  gener- 
ation of  trees  with  the  remains  of  other  plants,  forming  half  an  inch  or 
an  inch  of  coal ;  but  this  would  not  prevent  the  miner  from  affirming 
that  the  seam  a  g,  throughout  the  area  c  D,  was  equal  to  the  two  seams 
a'  and  g'  at  F. 

The  reader  has  seen,  by  reference  to  the  section  (fig.  505,  p.  390), 
that  the  strata  of  the  Appalachian  coal-field  assume  a  horizontal  posi- 
tion west  of  the  mountains.  In  that  less  elevated  country,  the  coal- 
measures  are  intersected  by  three  great  navigable  rivers,  and  are  capable 
of  supplying  for  ages,  to  the  inhabitants  of  a  densely  peopled  region,  an 
inexhaustible  supply  of  fuel.  These  rivers  are  the  Monongahela,  the 
Alleghany,  and  the  Ohio,  all  of  which  lay  open  on  their  banks  the  level 
seams  of  coal.  Looking  down  the  first  of  these  at  Brownsville,  we  have 
a  fine  view  of  the  main  seam  of  bituminous  coal  10  feet  thick,  commonly 
called  the  Pittsburg  seam,  breaking  out  in  the  steep  cliff  at  the  water's 
edge ;  and  I  made  the  accompanying  sketch  of  its  appearance  from  the 
bridge  over  the  river  (see  fig.  508).  Here  the  coal,  10  feet  thick,  is 
covered  by  carbonaceous  shale  (6),  and  this  again  by  micaceous  sand- 
stone (c).  Horizontal  galleries  may  be  driven  everywhere  at  very  slight 
expense,  and  so  worked  as  to  drain  themselves,  while  the  cars,  laden 
with  coal  and  attached  to  each  other,  glide  down  on  a  railway,  so  as  to 
deliver  their  burden  into  barges  moored  to  the  river's  bank.  The  same 
seam  is  seen  at  a  distance,  on  the  right  bank  (at  a),  and  may  be  fol- 
lowed the  whole  way  to  Pittsburg,  fifty  miles  distant.  As  it  is  nearly 
horizontal,  while  the  river  descends  it  crops  out  at  a  continually  increas- 
ing, but  never  at  an  inconvenient,  height  above  the  Monongahela.  Be- 
low the  great  bed  of  coal  at  Brownsville  is  a  fire-clay  1 8  inches  thick, 
and  below  this,  several  beds  of  limestone,  below  which  again  are  other 
coal  seams.  I  have  also  shown  in  my  sketch  another  layer  of  workable 
coal  (at  d  d),  which  breaks  out  on  the  slope  of  the  hills  at  a  greatei 
height.  Here  almost  every  proprietor  can  open  a  coal-pit  on  his  own 
land,  and  the  stratification  being  very  regular,  he  may  calculate  with 
•jrecision  the  depth  at  which  coal  may  be  won. 

The  Appalachian  coal-field,  of  which  these  strata  form  a  part  (from  c 


CH.  XXV.] 


APPALACHIAN  COAL  STEATA. 


£  S'S 

i  ! 


IF 

§  «* 


2  S  S 
^2* 
o!§ 

111 

^ll 
tf<j 


to  E,  section,  fig.  505,  p.  390),  is  remarkable  for  its  vast  area ;  for,  ac- 
cording to  Professor  H.  D.  Rogers,  it  stretches  continuously  from  N.  E. 
to  S.  W.,  for  a  distance  of  720  miles,  its  greatest  width  being  about  180 
miles.  On  a  moderate  estimate,  its  superficial  area  amounts  to  63,000 
square  miles. 

This  coal  formation,  before  its  original  limits  were  reduced  by  denu- 


394:  CONVEKSION  OF  COAL  INTO  LIGNITE.  [0*  XXV 

dation,  must  have  measured  900  miles  in  length,  and  in  some  places 
more  than  200  miles  in  breadth.  By  again  referring  to  the  section  (fig. 
505,  p.  390),  it  will  be  seen  that  the  strata  of  coal  are  horizontal  to  the 
westward  of  the  mountains  in  the  region  D  E,  and  become  more  and 
more  inclined  and  folded  as  we  proceed  eastward.  Now  it  is  invariably 
found,  as  Professor  H.  D.  Rogers  has  shown  by  chemical  analysis,  that 
the  coal  is  most  bituminous  towards  its  western  limit,  where  it  remains 
level  and  unbroken,  and  that  it  becomes  progressively  debituminized  as 
we  travel  southeastward  towards  the  more  bent  and  distorted  rocks. 
Thus,  on  the  Ohio,  the  proportion  of  hydrogen,  oxygen,  and  other  vola- 
tile matters,  ranges  from  forty  to  fifty  per  cent.  Eastward  of  this  line, 
on  the  Monongahela,  it  still  approaches  forty  per  cent.,  where  the  strata 
begin  to  experience  some  gentle  flexures.  On  entering  the  Alleghany 
Mountains,  where  the  distinct  anticlinal  axes  begin  to  show  themselves, 
but  before  the  dislocations  are  considerable,  the  volatile  matter  is  gene- 
rally in  the  proportion  of  eighteen  or  twenty  per  cent.  At  length,  when 
we  arrive  at  some  insulated  coal-fields  (5',  fig.  505)  associated  with  the 
boldest  flexures  of  the  Appalachian  chain,  where  the  strata  have  been 
actually  turned  over,  as  near  Pottsville,  we  find  the  coal  to  contain  only 
from  six  to  twelve  per  cent,  of  bitumen,  thus  becoming  a  genuine  an- 
thracite.* 

It  appears  from  the  researches  of  Liebig  and  other  eminent  chemists, 
that  when  wood  and  vegetable  matter  are  buried  in  the  earth,  exposed 
to  moisture,  and  partially  or  entirely  excluded  from  the  air,  they  decom- 
pose slowly  and  evolve  carbonic  acid  gas,  thus  parting  with  a  portion  of 
their  original  oxygen.  By  this  means,  they  become  gradually  converted 
into  lignite  or  wood-coal,  which  contains  a  larger  proportion  of  hydrogen 
than  wood  does.  A  continuance  of  decomposition  changes  this  lignite 
into  common  or  bituminous  coal,  chiefly  by  the  discharge  of  carburetted 
hydrogen,  or  the  gas  by  which  we  illuminate  our  streets  and  houses. 
According  to  Bischoff,  the  inflammable  gases  which  are  always  escaping 
from  mineral  coal,  and  are  so  often  the  cause  of  fatal  accidents  in  mines, 
always  contain  carbonic  acid,  carburetted  hydrogen,  nitrogen,  and  olifiant 
gas.  The  disengagement  of  all  these  gradually  transforms  ordinary  or 
bituminous  coal  into  anthracite,  to  which  the  various  names  of  splint- 
coal,  glance-coal,  hard  coal,  culm,  and  many  others,  have  been  giren. 

We  have  seen  that,  in  the  Appalachian  coal-field,  there  is  an  intimate 
connection  between  the  extent  to  which  the  coal  has  parted  with  its  gas- 
eous contents,  and  the  amount  of  disturbance  which  the  strata  have 
undergone.  The  coincidence  of  these  phenomena  may  be  attributed 
partly  to  the  greater  facility  afforded  for  the  escape  of  volatile  matter, 
where  the  fracturing  of  the  rocks  had  produced  an  infinite  number  of 
cracks  and  crevices,  and  also  to  the  heat  of  the  gases  and  water  pene- 
trating these  cracks,  when  the  great  movements  took  place,  which  have 
rent  and  folded  the  Appalachian  strata.  It  is  well  known  that,  at  the 

*  Trans,  of  Assoc.  of  Amer.  Geol.  p.  470. 


CH.  XXV.]  CLIMATE  OF  COAL  PEKIOD.  395 

present  period,  thermal  waters  and  hot  vapors  burst  out  from  the  earth 
during  earthquakes,  and  these  would  not  fail  to  promote  the  disengage- 
ment of  volatile  matter  from  the  carboniferous  rocks. 

Continuity  of  seams  of  coal. — As  single  seams  of  coal  are  continuous 
over  very  wide  areas,  it  has  been  asked,  how  forests  could  have  prevailed 
uninterruptedly  over  such  wide  spaces.  In  reply,  it  may  be  said  that 
swamp-forests  in  one  delta  may  extend  for  25,  50,  or  100  miles,  while  in 
a  contiguous  delta,  as  on  the  borders  of  the  Gulf  of  Mexico,  another  of 
precisely  the  same  character  may  l^  growing ;  and  these  may  in  after 
ages  appear  to  geologists  to  have  been  continuous,  although  in  fact  they 
were  simply  contemporaneous.  Denudation  may  easily  be  imagined  in 
such  cases  as  the  cause  of  interruptions,  which  were,  in  fact,  original. 
But  as  in  all  the  American  coal-fields  there  are  numerous  root-beds  with- 
out any  superincumbent  coal,  we  may  presume  that  frequently  layers  of 
vegetable  matter  were  removed  by  floods  ;  and  in  other  cases,  where  the 
stigmaria-clays  are  for  a  certain  space  covered  with  coal,  and  then  pro- 
longed without  any  such  covering,  the  inference  of  partial  denudation  is 
still  more  obvious. 

In  the  Forest  of  Dean,  ancient  river-channels  are  found,  which  pass 
through  beds  of  coal,  and  in  which  rounded  pebbles  of  coal  occur. 
They  are  of  older  date  than  the  overlying  and  undisturbed  coal-measures. 
The  late  Mr.  Buddie,  who  described  them  to  me,  told  me  he  had  seen 
similar  phenomena  in  the  Newcastle  coal-field.  Nevertheless,  instances  of 
these  channels  are  much  more  rare  than  we  might  have  anticipated,  espe- 
pecially  when  we  remember  how  often  the  roots  of  trees  (Stigmarice) 
have  been  torn  up,  and  drifted  in  broken  fragments  into  the  grits  and 
sandstones.  The  prevalence  of  a  downward  movement  is,  no  doubt,  the 
principal  cause  which  has  saved  so  many  extensive  seams  of  coal  from 
destruction  by  fluviatile  action. 

Climate  of  Coal  Period. — So  long  as  the  bonanist  taught  that  a  tropi- 
cal climate  was  implied  by  the  carboniferous  flora,  geologists  might  well 
be  at  a  loss  to  reconcile  the  preservation  of  so  much  vegetable  matter  with 
a  high  temperature  ;  for  heat  hastens  the  decomposition  of  fallen  leaves 
and  trunks  of  trees,  whether  in  the  atmosphere  or  in  water.  It  is  well 
known  that  peat,  so  abundant  in  the  bogs  of  high  latitudes,  ceases  to  grow 
in  the  swamps  of  warmer  regions.  It  seems,  however,  to  have  become 
a  more  and  more  received  opinion,  that  the  coal-plants  do  not,  on 
the  whole,  indicate  a  climate  resembling  that  now  enjoyed  in  the  equa- 
torial zone.  Tree-ferns  range  as  far  south  as  the  southern  part  of  New 
Zealand,  and  Araucarian  pines  occur  in  Norfolk  Island.  A  great  pre- 
dominance of  ferns  and  lycopodiums  indicates  moisture,  equability  of 
temperature,  and  freedom  from  frost,  rather  than  intense  heat ;  and  we 
know  too  little  of  the  sigillariae,  calamites,  asterophyllites,  and  other 
peculiar  forms  of  the  carboniferous  period,  to  be  able  to  speculate  with 
confidence  on  the  kind  of  climate  they  may  have  required. 

The  same  may  be  said  of  the  corals  and  cephalopoda  of  the  Moun- 
tain Limestone, — they  belong  to  families  of  whose  climatal  habits  we  know 


396  CAEBONIFEKOUS  KEPTILES.  [CH-  XXV. 

nothing ;  and  even  if  they  should  be  thought  to  imply  that  a  warm  tem- 
perature characterized  the  northern  seas  in  the  carboniferous  era,  the 
absence  of  cold  may  have  given  rise  (as  at  present  in  the  seas  of  the  Ber- 
mudas, under  the  influence  of  the  Gulf-stream)  to  a  very  wide  geographical 
rang£  of  stone-building  corals  and  shell-bearing  cuttle-fish,  without  its 
being  necessary  to  call  in  the  aid  of  tropical  heat. 

CARBONIFEROUS    REPTILES. 

"Where  we  have  evidence  in  a  single  coal-field,  as  in  that  of  Nova 
Scotia,  or  of  South  Wales,  of  fifty  or  even  a  hundred  ancient  forests  buried 
one  above  the  other,  with  the  roots  of  trees  still  in  their  original  position, 
and  with  some  of  the  trunks  still  remaining  erect,  we  are  apt  to  wonder 
that  until  the  year  1844  no  remains  of  contemporaneous  air-breathing 
creatures  should  have  been  discovered.  No  vertebrated  animals  more 
highly  organized  than  fish,  no  mammalia  or  birds,  no  saurians,  frogs,  tor- 
toises, or  snakes  were  known  in  rocks  of  such  high  antiquity.  In  the 
coalfields  of  Europe  mention  has  been  made  of  beetles,  locusts,  and  a  few 
other  insects,  but  no  land-shells  have  even  now  been  met  with.  Agassiz 
described  in  his  great  work  on  fossil  fishes  more  than  one  hundred  and 
fifty  species  of  ichthyolites  from  the  coal-strata,  ninety-four  belonging  to 
the  families  of  shark  and  ray,  and  fifty-eight  to  the  class  of  ganoids. 
Some  of  these  fish  are  very  remote  in  their  organization  from  any  now 
living,  especially  those  of  the  family  called  Sauroid  by  Agassiz ;  as 
Megalichthys,  Holoptychius,  and  others,  which  were  often  of  great  size, 
and  all  predaceous.  Their  osteology,  says  M.  Agassiz,  reminds  us  in 
many  respects  of  the  skeletons  of  saurian  reptiles,  both  by  the  close 
sutures  of  the  bones  of  the  skull,  their  large  conical  Fj  509 

teeth  striated  longitudinally  (see  fig.  509),  the  ar- 
ticulations of  the  spinous  processes  with  the  verte- 
bra, and  other  characters.  Yet  they  do  not  form 
a  family  intermediate  between  fish  and  reptiles,  but 
are  true  fish,  though  doubtless  more  highly  organ- 
ized than  any  living  fish.* 

The  annexed  figure  represents  a  large  tooth  of 
the  Holoptychius,  found  by  Mr.  Homer,  in  the 
Cannel  coal  of  Fifeshire.  This  fish  probably  in- 
habited an  estuary,  like  many  of  its  contemporaries, 
and  frequented  both  rivers  and  the  sea. 

At  length,  in  1844,  the  first  skeleton  of  a  true 
reptile  was  announced  from  the  coal  of  Miinster- 
Appel  in  Ehenish  Bavaria,  by  H.  von  Meyer,  under 
the  name  of  Apateon  pedestris,  the  animal  being         Fifeshire  coal-field.    { 
supposed  to  be  nearly  related  to  the  salamanders. 

Three  years  later,  in  1847,  Prof,  von  Dechen  found  in  the  coal-field  of 
Saarbruck,  at  the  village  of  Lebach,  between  Strasburg  and  Treves, 

*  Agassiz,  Poiss.  Foss.  vol.  ii.  p.  88,  <fec. 


CH.  XXV.] 


CARBONIFEROUS   REPTILES. 


397 


Fig.  510. 


the  skeletons  of  no  less  than  three  distinct  species  of  air-breathing  reptiles, 
which  were  described  by  the  late  Prof.  Goldfuss  under  the  generic  name 
of  Archegosaurus.  The  ichthyolites  and  plants  found  in  the  same  strata 
left  no  doubt  that  these  re- 
mains belonged  to  the  true 
coal  period.  The  skulls,  teeth, 
and  the  greater  portions  of 
the  skeleton,  nay,  even  a  large 
part  of  the  skin,  of  two  of 
these  reptiles  have  been  faith- 
fully preserved  in  the  centre 
of  spheroidal  concretions  of 
clay-iron-stone.  The  largest 
of  these  lizards,  Archegosau- 
rus Decheni,  must  have  been 
3  feet  6  inches  long.  The 
annexed  drawing  represents 
the  skull  and  neck  bones  of 
the  smallest  of  the  three,  of 
the  natural  size.  They  were 
considered  by  Goldfuss  as 
saurians,  but  by  Herman  von 
Meyer  as  most  nearly  allied 
to  the  Ldbyrinthodon,  and 
therefore,  as  before  explained 
(p.  340),  having  many  char- 
acters intermediate  between 
batrachians  and  saurians.  The 
remains  of  the  extremities 
leave  no  doubt  that  they  were  quadrupeds,  "  provided,"  says  von  Meyer, 
"  with  hands  and  feet  terminating  in  distinct  toes  ;  but  these  limbs  were 
weak,  serving  only  for  swimming  or  creeping."  The  same  anatomist  has 
pointed  out  certain  points  of  analogy  be-  Fi  „ 

tween  their  bones  and  those  of  Proteus 
anguinus  ;  and  Prof.  Owen  has  observed 
to  me  that  they  make  an  approach  to  the 
Proteus  in  the  shortness  of  their  ribs.  Two 
specimens  of  these  ancient  reptiles  retain  a 
large  part  of  the  outer  skin,  which  con- 
sisted of  long,  narrow  wedge-shaped,  tile-like,  and  horny  scales,  arranged 
in  rows.  (See  fig.  51L) 

Cheirotherian  footprints  in  coal-measures,  United  States. — In  1844, 
the  very  year  when  the  Apateon  or  Salamander  of  the  coal  was  first  met 
with  in  the  country  between  the  Moselle  and  the  Khine,  Dr.  King  pub- 
lished an  account  of  the  footprints  of  a  large  reptile  discovered  by  him 

*  Ooldfuss,  Neue  Jenaische  Lit.  Zeit.  1848 ;  aud  Von  Meyer,  Quart.  GeoL 
Journ.  voL  iv.  Miscell.  p.  61. 


Archegosauiw  minor,  Goldfnss.    Fossil  reptile  from 
the  coal-measures,  Saarbriick. 


Imbricated  covering  of  skin  of  Archf* 

gosaurus  medius,  Gold! ; 

magnified* 


398 


FOOTPKENTS  OF 

Fig.  512. 


[Cn.  XXV. 


Scale  one-sixth  th#  original. 

Slab  of  sandstone  from  the  coal-measures  of  Pennsylvania,  with  footprints  of 
air-breathing  reptile  and  casts  of  cracks. 

in  North  America.  These  occur  in  the  coal  strata  of  Greensburg,  in 
Westmoreland  county,  Pennsylvania ;  and  I  had  an  opportunity  of  ex- 
amining them  in  1846.  I  was  at  once  convinced  of  their  genuineness, 
and  declared  my  conviction  on  that  point,  on  which  doubts  had  been 
entertained  both  in  Europe  and  the  United  States.  The  footmarks  were 
first  observed  standing  out  in  relief  from  the  lower  surface  of  slabs  of 
sandstone,  resting  on  thin  layers  of  fine  unctuous  clay.  I  brought  away 
one  of  these  masses,  which  is  represented  in  the  accompanying  drawing 
(fig.  512).  It  displays,  together  with  footprints,  the  casts  of  cracks  (a,  a') 
of  various  sizes.  The  origin  of  such  cracks  in  clay,  and  casts  of  the 
same,  has  before  been  explained,  and  referred  to  the  drying  and  shrinking 
of  mud,  and  the  subsequent  pouring  of  sand  into  open  crevices.  It  will 
be  seen  that  some  of  the  cracks,  as  at  5,  c,  traverse  the  footprints,  and 
produce  distortion  in  them,  as  might  have  been  expected,  for  the  mud 
must  have  been  soft  when  the  animal  walked  over  it  and  left  the  impres- 


Ca   XXV.J 


AIR-BREATHING  REPTILES. 
Fig.  513. 


399 


Series  of  reptilian  footprints  in  the  coal-strata  of  "Westmoreland 
county,  Pennsylvania. 

a.  Mark  of  nail? 

sions ;  whereas,  when  it  afterwards  dried  up  and  shrank,  it  would  be  too 
hard  to  receive  such  indentations. 

No  less  than  twenty-three  footsteps  were  observed  by  Dr.  King  in  the 
same  quarry  before  it  was  abandoned,  the  greater  part  of  them  so  ar- 
ranged (see  fig.  513)  on  the  surface  of  one  stratum  as  to  imply  that 
they  were  made  successively  by  the  same  animal.  Everywhere  there 
was  a  double  row  of  tracks,  and  in  each  row  they  occur  in  pairs,  each 
pair  consisting  of  a  hind  and  fore  foot,  and  each  being  nearly  equal 


400  FOOTPKINTS  OF  EEPTILIANS.  [Cn.  XXV 

distances  from  the  next  pair.  In  each  parallel  row  the  toes  turn  the  one 
set  to  the  right,  the  other  to  the  left.  In  the  European  Cheirotherium, 
before  mentioned  (p.  337),  both  the  hind  and  the  fore  feet  have  each  five 
toes,  and  the  size  of  the  hind  foot  is  about  five  times  as  large  as  the  fore 
foot.  In  the  American  fossil  the  posterior  footprint  is  not  even  twice  as 
large  as  the  anterior,  and  the  number  of  toes  is  unequal,  being  five  in  the 
hinder  and  four  in  the  anterior  foot.  In  this,  as  in  the  European  Cheiro- 
therium,  one  toe  stands  out  like  a  thumb,  and  these  thumb-like  toes  turn 
the  one  set  to  the  right,  and  the  other  to  the  left.  The  American 
Cheirotherium  was  evidently  a  broader  animal,  and  belonged  to  a  dis- 
tinct genus  from  that  of  the  triassic  age  in  Europe.* 

We  may  assume  that  the  reptile  which  left  these  prints  on  the  ancient 
sands  of  the  coal-measures  was  an  air-breather,  because  its  weight  would 
not  have  been  sufficient  under  water  to  have  made  impressions  so  deep 
and  distinct.  The  same  conclusion  is  also  borne  out  by  the  casts  of  the 
cracks  above  described,  for  they  show  that  the  clay  had  been  exposed  to 
the  air  and  sun,  so  as  to  have  dried  and  shrunk. 

The  geological  position  of  the  sandstone  of  Greensburg  is  perfectly 
clear,  being  situated  in  the  midst  of  the  Appalachian  coal-field,  having 
the  main  bed  of  coal,  called  the  Pittsburg  seam,  above  mentioned  (p. 
392),  three  yards  thick,  100  feet  above  it,  and  worked  in  the  neighbor- 
hood, with  several  other  seams  of  coal  at  lower  levels.  The  impressions 
of  Lepidodendron,  Sigillaria,  Stigmaria,  and  other  characteristic  car- 
boniferous plants  are  found  both  above  and  below  the  level  of  the  reptil- 
ian footsteps. 

Analogous  footprints  of  a  large  reptile  of  still  older  date  were  after- 
wards found  (1849)  at  Pottsville,  70  miles  N.  E.  of  Philadelphia,  by  Mr. 
Isaac  Lea,  in  a  formation  of  red  shales,  called  Ko.  XL  by  Prof.  H.  D. 
Rogers,  in  the  State  Survey  of  Pennsylvania,  and  referred  by  him  to  the 
base  of  the  coal,  but  regarded  by  some  geologists  as  the  uppermost  part 
of  the  Old  Red  Sandstone.  A  thickness  of  1700  feet  of  strata  intervenes 
between  the  footprints  of  Greensburg,  before  described,  and  these  older 
Pottsville  impressions.  In  the  same  Red  Shale,  No.  XL,  the  "  debatable 
ground"  between  the  Carboniferous  and  Devonian  group,  Prof.  H.  D. 
Rogers  announced  in  1851  that  he  had  discovered  other  footprints,  re- 
ferred by  him  to  three  species  of  quadrupeds,  all  of  them  five-toed  and  in 
double  rows,  with  an  opposite  symmetry,  as  if  made  by  right  and  left 
feet,  while  they  likewise  display  the  alternation  of  fore  foot  and  hind  foot. 
One  species,  the  largest  of  the  three,  presents  a  diameter  for  each  foot- 
print of  about  two  inches,  and  shows  the  fore  and  hind  feet  to  be  nearly 
equal  in  dimensions.  It  exhibits  a  length  of  stride  of  about  nine  inches, 
and  a  breadth  between  the  right  and  left  footsteps  of  nearly  four  inches. 
The  impressions  of  the  hind  feet  are  but  little  in  the  rear  of  the  fore  feet. 
The  animal  which  made  them  is  supposed  to  have  been  allied  to  a  Sau- 
rian, rather  than  to  a  Batrachian  or  Chelonian.  With  these  footmarks 
*vere  seen  shrinkage  cracks,  such  as  are  caused  by  the  sun's  heat  in  mud. 

*  See  Lyell's  Second  Visit,  &c.,  vol.  ii.  p.  305. 


CH.  XXV.]  AIR-BREATHERS  IN  THE  COAL.  401 

and  rain-spots,  with  the  signs  of  the  trickling  of  water  on  a  wet,  sandy 
beach ;  all  confirming  the  conclusion  derived  from  the  footprints,  that  the 
quadrupeds  belonged  to  air-breathers,  and  not  to  aquatic  races. 

In  1852  the  first  osseous  remains  of  a  reptile  were  obtained  from  the 
coal-measures  of  America  by  Mr.  Dawson  and  myself.  We  detected 
them  in  the  interior  of  one  of  the  erect  Sigillariae  before  alluded  to  as  of 
such  frequent  occurrence  in  Nova  Scotia.  The  tree  was  about  two  feet 
in  diameter,  and  consisted,  as  usual,  of  an  external  cylinder  of  bark,  con- 
verted into  coal,  and  an  internal  stony  axis  of  black  sandstone,  or  rather 
mud  and  sand  stained  black  by  carbonaceous  matter,  and  cemented  to- 
gether with  fragments  of  wood  into  a  rock.  These  fragments  were  in 
the  state  of  charcoal,  and  seem  to  have  fallen  to  the  bottom  of  the  hollow 
tree  while  it  was  rotting  away.  The  skull,  jaws,  and  vertebrae  of  a  rep- 
tile, probably  about  2J  feet  in  length  (Dendrerpeton  Acadianum,  Owen), 
were  scattered  through  this  stony  matrix.  The  shell  also  of  a  Pupa,  the 
first  pulmoniferous  mollusk  ever  met  with  in  the  coal,  was  observed  in  the 
same  stony  mass.  Dr.  Wyman,  of  Boston,  pronounced  the  reptile  to  be 
allied  in  structure  to  Menobranchus  and  Menopoma,  species  of  batra- 
chians,  now  inhabiting  the  North  American  rivers.  The  same  view  was 
afterwards  confirmed  by  Prof.  Owen,  who  also  pointed  out  the  resem- 
blance of  the  cranial  plates  to  those  seen  in  the  skull  of  Archegosaurus 
and  Labyrinthodon.*  Whether  the  creature  had  crept  into  the  hollow 
tree  while  its  top  was  still  open  to  the  air,  or  whether  it  was  washed  in 
with  mud  during  a  flood,  or  in  whatever  other  manner  it  entered,  must 
be  matter  of  conjecture. 

Footprints  of  two  reptiles  of  different  sizes  had  previously  been  ob- 
served by  Dr.  Harding  and  Dr.  Gesner  on  ripple-marked  flags  of  the 
lower  coal-measures  in  Nova  Scotia,  evidently  made  by  quadrupeds  walk- 
ing on  the  ancient  beach,  or  out  of  the  water,  just  as  the  recent  Meno- 
poma is  sometimes  observed  to  do. 

In  1853  Prof.  Owen  announced  the  first  discovery  of  fossil  reptilian 
remains  in  the  British  Coal-Measures;  and,  in  1854,  the  same  osteologist 
described  a  "  sauroid  batrachian,"  of  the  Labyrinthodon  family,  obtained 
by  Mr.  Dawson,  from  the  coal  of  Pictou,  in  Nova  Scotia. 

Thus  in  ten  years  (between  1844  and  1854)  the  skeletons  or  bones  of 
no  less  than  seven  carboniferous  reptiles,  referred  to  five  genera,  were 
brought  to  light ;  to  say  nothing  of  numerous  reptilian  footprints,  some 
of  them  too  large  to  belong  to  the  same  species  as  the  bones. 

Rarity  of  vertebrate  and  invertebrate  Air-breathers  in  Coal 

Before  the  earliest  date  above  mentioned  (1844),  it  was  common  to 
hear  geologists  insisting  on  the  non-existence  of  vertebrate  anirtals  of  a 
higher  grade  than  fishes  in  the  Coal,  or  in  any  rocks  older  than  the  Per- 
mian. Even  now,  it  may  be  said,  that  we  have  scarcely  made  any  pro- 

*  Geol.  Quart.  Journ.  vol.  ix.  p.  58. 
26 


402  AIR-BREATHERS  IN  THE   COAL  [On.  XXV 

gress  in  obtaining  a  knowledge  of  the  terrestrial  fauna  of  the  coal,  since 
the  reptiles  above  enumerated  seem  to  have  been  all  amphibious.  Nega- 
tive evidence  should  have  its  due  weight  in  paleontological  reasonings 
and  speculations,  but  we  are  as  yet  quite  unable  to  appreciate  its  value. 
In  the  United  States  about  five  millions  of  tons  of  native  coal  are  annually 
extracted  from  the  coal-measures,  yet  no  fossil  insect  has  yet  been  met 
with  in  the  carboniferous  rocks  of  North  America.  Ought  we  then  to 
conclude  that  at  the  period  of  the  coal  insects  were  unrepresented  in  the 
forests  of  the  Western  World  ?  In  like  manner,  no  land-shell,  no  Helix, 
Bulimus,  Pupa,  or  Clausilia,  nor  any  aquatic  pulmoniferous  mollusk,  such 
as  Limneus  or  Planorbis,  is  recorded  to  have  come  from  the  coal  of 
Europe,  worked  for  centuries  before  America  was  discovered,  and  now 
quarried  on  so  enormous  a  scale.  '  Can  we  infer  that  land-shells  were  not 
called  into  existence  in  European  latitudes  until  after  the  carboniferous 
period  ? 

The  theory  of  progressive  development  would  account  readily  for  the 
absence  of  Chelonian  and  Saurian  reptiles,  or  of  Birds  and  Mammals, 
from  the  Coal-Measures,  because  the  condition  of  the  planet  is  supposed 
to  have  been  too  immature  and  unsettled  to  permit  creatures  enjoying  a 
higher  development  than  batrachians  to  find  a  fit  domicile  therein.  But 
this  same  theory  leaves  the  scarcity  of  the  invertebrata,  or  the  entire  ab- 
sence of  many  important  classes  of  them,  wholly  unexplained.  When 
we  generalize  on  this  subject,  we  must  not  forget  that  the  eighteen  or 
twenty  individual  insects  and  land- shells  met  with  in  the  coal  (and  most 
of  these  very  recently  found),  are  scarcely  double  the  number  of  the  car- 
boniferous reptiles  which  have  been  established  within  the  last  ten  years 
on  the  evidence  of  bones  and  footprints.  Yet  our  opportunities  of  ex- 
amining strata  formed  in  close  connection  with  ancient  land  exceed  in 
this  case  all  that  we  enjoy  in  regard  to  any  other  formations,  whether 
primary,  secondary,  or  tertiary.  We  have  ransacked  hundreds  of  soils 
replete  with  the  fossil  roots  of  trees, — have  dug  out  hundreds  of  erect 
trunks  and  stumps,  which  stood  in  the  position  in  which  they  grew, — 
have  broken  up  myriads  of  cubic  feet  of  fuel  still  retaining  its  vegetable 
structure, — and,  after  all,  we  continue  almost  as  much  in  the  dark  re- 
specting the  invertebrate  air-breathers  of  this  epoch,  as  if  the  Coal  had 
been  thrown  down  in  mid-ocean.  The  age  of  the  planet,  or  its  unpre- 
pared state  to  serve  as  a  dwelling-place  for  organized  beings,  cannot  ex- 
plain the  enigma,  because  we  know  that  while  the  land  supported  a  lux- 
uriant vegetation,  the  contemporaneous  seas  swarmed  with  life — with 
Articulata,  Mollusca,  Radiata,  and  Fishes.  We  must,  therefore,  collect 
more  facts,  if  we  expect  to  solve  a  problem,  which,  in  the  present  state  of 
science,  cannot  but  excite  our  wonder;  and  we  must  remember  how 
much  the  conditions  of  this  problem  have  varied  within  the  last  ten 
years.  Meanwhile  let  us  be  content  to  impute  the  scantiness  of  our  data, 
chiefly  to  our  want  of  skill  as  collectors  and  interpreters,  but  partly  also 
to  our  ignorance  of  the  laws  which  govern  the  fossilization  of  land- 
animals,  whether  of  high  or  low  degree. 


CH.  XXV.] 


MOUNTAIN  LIMESTONE. 


403 


CARBONIFEROUS    OR   MOUNTAIN   LIMESTONE. 

It  has  been  already  stated  (p.  359),  that  this  formation  underlies  the 
Coal-Measures  in  the  South  of  England  and  Wales,  whereas  in  the  North 
and  in  Scotland  marine  limestones  alternate  with  Coal-Measures,  or  with 
shales  and  sandstones,  sometimes  containing  seams  of  Coal.  In  its  most 
calcareous  form  the  Mountain  Limestone  is  destitute  of  land-plants,  and 
is  loaded  with  marine  remains, — the  greater  part,  indeed,  of  the  rock 
being  made  up  bodily  of  corals  and  crinoids. 

The  Corals  deserve  especial  notice,  as  the  cup-shaped  kinds,  which 
have  the  most  massive  and  stony  skeletons,  display  peculiarities  of  struc- 
ture by  which  they  may  be  distinguished,  as  MM.  Milne  Edwards  and 
Haime  first  pointed  out,  from  all  species  found  in  strata  newer  than  the 
Permian.  There  is,  in  short,  an  ancient  or  Paleozoic,  and  a  modern  or 
Neozoic  type,  if,  by  the  latter  term,  we  designate  (as  proposed  by  Prof. 
E.  Forbes)  all  strata  from  the  triassic  to  the  most  modern,  inclusive.  The 
accompanying  diagrams  (figs.  514,  515)  may  illustrate  these  types  ;  and, 
although  it  may  not  always  be  easy  for  any  but  a  practised  naturalist  to 

Fig.  514. 

Paleozoic  type  of  lamelliferous  cup-shaped  Coral.    Order  ZOANTHARIA  ECGOSA,  Milne  Edwards 
and  Jules  Haime. 

a.  Vertical  section  of  Campophyllum  flexuosum  (Cyatho- 
phyllum,  Goldfuss);  £  nat  size:  from  the  Devonian  of 
the  Eifel.  The  lamella*  are  seen  around  the  inside  of  the 
cup;  the  walls  consist  of  cellular  tissue :  and  large  trans- 
verse plates,  called  tabulce,  divide  the  interior  into  cham- 
bers. 

6.  Arrangement  of  the  lamella  in  Polyccdia  prof  undo,,  Ger- 
mar,  sp. ;  nat  size:  from  the  Magnesian  Limestone,  Dur- 
ham. This  diagram  shows  the  quadripartite  arrangement 
of  the  lamellae  characteristic  of  paleozoic  corals,  there  being 
four  principal  and  eight  intermediate  lamella?,  the  whole 
number  in  this  type  being  always  a  multiple  of  four. 

c.  Stauria  astrceceformis,  Milne  Edwards.  Young  group, 
nat  size.  Upper  Silurian,  Gothland.  The  lamellae  in 
each  cup  are  divided  by  four  prominent  ridges  into  four 
groups. 

Fig.  515. 

Neozoic  type  of  lamelliferons  cup-shaped  Coral.    Order  ZOAXTHAEIA  APOBOSA,  M.  Edwards  and 

J.  Haitne. 

a.  Para&nttia  centrali*,  Man  tell,  sp.  Vertical  section,  nat  size. 
Upper  Chalk,  Gravesend.  In  this  type  the  lamellae,  are  mas- 
sive, and  extend  to  the  axis  of  loose  cellular  tissue,  without 
any  transverse  plates  like  those  in  fig.  514  a. 

J.  Cyathina  Bowerbankii,  Edwards  and  Haime.  Transverse 
section,  enlarged.  Gault  Folkstone.  In  this  coral  the  lameUm 
are  a  multiple  of  six.  The  twelve  principal  plates  reach  the 
central  axis  or  columella,  and  between  each  pair  there  are 


three  secondary  plates,  in  all  forty-eight  The  short  interme- 
diate plates  which  proceed  from  the  columella  are  not  counted. 
They  are  ca,\\ed  pali. 

c.  Fungia  patettaris,  Lamk.  Eecent :  very  young  state.  Dia- 
gram of  its  six  principal  and  six  intermediate  septa,  magnified. 
The  sextuple  arrangement  is  always  more  manifest  in  the 
young  than  in  the  adult  state. 

recognize  the  points  of  structure  here  described,  every  geologist  should 
understand  them,  as  the  reality  of  the  distinction  is  of  no  small  theoreti- 
cal interest. 


404: 


FOSSILS  OF  THE 


[Cn.  XXT. 


ft  will  be  seen  that  the  more  ancient  corals  have  what  is  called  a 
quadripartite  arrangement  of  the  stony  plates  or  lamellae, — parts  of  the 
skeleton  which  support  the  organs  of  reproduction.  The  number  of 
these  lamellae  in  the  paleozoic  type  is  4,  8,  16,  &c.  \  while  in  the  newer 
type  the  number  is  always  6,  12,  24,  or  some  other  multiple  of  six ;  and 
this  holds  good,  whether  they  be  simple  cup-like  forms,  as  in  figs.  514  a 
and  515  a,  or  aggregate  clusters  of  cups  as  in  514  c. 

It  is  not  enough,  therefore,  to  say  that  the  primary  or  more  ancient 
corals  are  all  generically  and  specifically  dissimilar  from  the  secondary, 
tertiary,  and  living  corals, — for,  more  than  this,  they  belong  to  distinct 
Orders,  although  often  so  like  in  outward  form  as  to  have  been  referred 
in  many  cases  to  living  reef-building  genera.  Hence  we  must  not  too 
confidently  draw  conclusions  from  the  modern  to  the  paleozoic  polyps, 
respecting  climate  and  the  temperature  of.  the  waters  of  the  primeval 
seas,  inasmuch  as  the  two  groups  of  zoophytes  are  constructed  on  essen- 
tially different  types.  When  the  great  number  of  the  paleozoic  and  neo- 
zoic species  is  taken  into  account,  it  is  truly  wonderful  to  find  how  con- 
stant the  rule  above  explained  holds  good  ;  only  one  exception  having  as 
yet  occurred  of  a  quadripartite  coral  in  a  neozoic  formation  (the  creta- 
ceous), and  one  only  of  the  sextuple  class  (a  Fungia  ?}  in  paleozoic 
(Silurian)  rocks. 

From  a  great  number  of  lamelliferous  corals  met  with  in  the  Mountain 
Limestone,  two  species  have  been  selected,  as  having  a  very  wide  range, 
extending  from  the  eastern  borders  of  Russia  to  the  British  Isles,  and 
being  found  almost  everywhere  in  each  country. 


Fig.  516. 


Fig.  517. 


Lithostrotion  Ixitaltiforme,  Phil.  sp.  (Li- 
thostrotion  striatum,  Fleming ;  Astrcea 
basaltiformis,  Couyb.  and  Phill.)  Ken- 
dal;  Ireland;  Russia;  Iowa,  and  west- 
ward of  the  Mississippi,  "United  States. 
(D.  D.  Owen.) 


Lonsclateia  Jtoriformis  (Martin,  sp.) 
M.  Edwards.  (Lithostrotionfloriforme, 
Fleming.  Strombodes.*) 

a.  Young  specimen,  with  buds  on  the 
disk. 

"b.  Part  of  a  full-grown  compound  mass. 
Bristol,  &c. ;  Eussia. 


These  fossils,  together  with  numerous  species  of  Zaphrentis,  Amplexus. 
Cyathophyllum,  Clisiophyllum,  Syringopora,  and  Michdinea*  form  a 
group  widely  different  from  any  that  preceded  or  followed  them. 

*  For  figures  of  these  corals,  see  Paleontographical  Society's  Monographs,  1852, 


Cn.  XXV.] 


MOUNTAIN    LIMESTONE. 


405 


Of  the  Bryozoa,  the  prevailing  forms  are  Fenestella  and  Polypora,  and 
these  often  form  considerable  beds.  Their  net-like  fronds  are  easily  rec- 
ognized. 

Crinoidea  are  also  numerous  in  the  Mountain  Limestone.  (See  figs. 
518,519.) 


Fig.  518. 


Fig.  519. 


Cyatfiocrinitts  planuz, 
Miller.     Body  and 
arms.      Mountain 
Limestone. 


Cyathocrinu*  caryocrinoidei,  M'Coy. 
a.  Surface  of  one  of  the  joints  of  the  stem. 
6.  Pelvis  or  body;  called  also  calyx  or  cup. 
c.  One  of  the  pelvic  plates. 


In  the  greater  part  of  them,  the  cup  or  pelvis,  fig.  519  .6,  is  greatly 
developed  in  size  in  proportion  to  the  arms,  although  this  is  not  the  case 
in  fig.  518.  The  genera  Poteriocrinus,  Cyathocrinus,  Pentremites, 
Actinocrinus,  and  Platycrinus,  are  all  of  them  characteristic  of  this 
formation.  'Other  Echinoderms  are  rare,  a  few  Sea-Urchins  only  being 
known  :  these  have  a  complex  structure,  with  many  more  plates  on  their 
surface  than  are  seen  in  the  modern  genera  of  the  same  group.  One 
genus,  the  Palcechinus  (fig.  520)  is  the  analogue  of  the  modern  Echinus. 
The  other,  Archceocidaris,  represents,  in  like  manner,  the  Cidaris  of  the 
present  seas. 

Of  Mollusca  the  Brachiopoda,  (or  Palliobranchiates)  constitute  the 
larger  part,  and  are  not  only  numerous,  but  often  of  large  size.  Perhaps 
the  most  characteristic  shells  of  the  formation  are  large  species  of  Pro 
ductus,  such  as  P.  giganteus,  P.  hemisphcericus,  P.  semireticulatus  (fig. 
521),  and  P.  scabriculus.  Large  plaited  spirifers,  as  Spirifer  siriatus, 


Fig.  521. 


Fig  520. 


fAUxoAinus  gigas,  M'Coy.    Eeduced. 
Mountain  Limestone : 
Ireland. 


Producing  semireticulatus,  Martin,  sp. 
(P.  antiquatu*.  Sow.)  Mountain 
Limestone.  England  ;  Enssia ;  the 
Andes,  &c. 


406 


FOSSILS  OF  THE 


[On.  XXV 


£.  rotundatus,  and  S.  trigonalis  (fig.  522),  also  abound ;  and  smooth 
species,  such  as  Spirifer  glaber  (fig.  523),  with  its  numerous  varieties- 


Fig.  523. 


Spirifer  trigonalis,  Martin,  sp. 
Mountain  Limestone  :  Derbyshire,  &c. 


Spirifer  glaber,  Martin,  sp. 
Mountain  Limestone. 


Among  the  palliobranchiate  mollusks,  Terebratula  hastata  deserves 
mention,  not  only  for  its  wide  range,  but  because  it  often  retains  the  pat- 
tern of  the  original  colored  stripes  which  ornamented  the  living  shell. 
(See  fig.  524.)  These  colored  bands  are  also  preserved  in  several  lamel- 
libranchiate  bivalves,  as  in  Aviculopecten  (fig.  525),  in  which  dark  stripes 
alternate  with  a  light  ground.  In  some  also  of  the  spiral  univalves,  the 
pattern  of  the  original  painting  is  distinctly  retained,  as  in  the  Pleuroto- 
maria  (fig.  526),  which  displays  wavy  blotches,  resembling  the  coloring 
in  many  recent  Trochidse. 


Fig.  524. 


Fig.  525. 


Terebratula  hastata, 
Sow.,  with  radiating 
bands  of  color. 
Mountain  Lime- 
stone. Derbyshire : 
Ireland ;  Kussia,  &c. 


Aviculopecten  sublobatus, 
Phill.  Mountain  Lime- 
stone. Derbyshire ; 
Yorkshire. 


Pleurotomaria  carinata,  Sow, 

(P.jlammigera,  Phill.) 
Mountain  Limestone.  Derby- 
shire, &c. 


The  mere  fact  that  shells  of  such  high  antiquity  should  have  preserved 
the  patterns  of  their  coloring,  is  striking  and  unexpected  ;  but  Prof.  E. 
Forbes  has  deduced  from  it  an  important  geological  conclusion.  He 
infers  that  the  depth  of  the  primeval  seas  in  which  the  Mountain  Lime- 
stone was  formed,  did  not  exceed  50  fathoms.  To  this  opinion  he  is  led 
by  observing,  that  in  the  existing  seas  the  testacea  which  have  colors 
and  well-defined  patterns,  rarely  inhabit  greater  depths  than  50  fathoms ; 
and  the  greater  number  are  found  where  there  is  most  light  in  very 
shallow  water,  not  more  than  two  fathoms  deep.  There  are  even  exam- 
ples in  the  British  seas  of  testacea  which  are  always  white  or  colorless 
when  taken  from  below  100  fathoms ;  and  yet  individuals  of  the  same 
species,  if  taken  from  shallower  zones,  are  vividly  striped  or  banded. 


CH.  XXV.] 


MOUNTAIN  LIMESTONE. 


407 


This  information,  derived  from  the  color  of  the  shells,  is  the  more 
welcome,  because  the  Kadiata,  Articulata,  and  Mollusca  of  the  Carbo- 
niferous* period  belong  almost  entirely  to  genera  no  longer  found  in  the 
living  creation,  and  respecting  the  habits  of  which  we  can  only  hazard 
conjectures. 

Some  few  of  the  carboniferous  mollusca,  such  as  Avicula,  Nucula, 
Soiemya,  and  Lithodomus,  belong  no  doubt  to  existing  genera ;  but  the 
majority,  though  often  referred  to  living  types,  such  as  Isocardia,  Turri- 
tella,  and  Buccinum,  belong  really  to  forms  which  appear  to  have  become 
extinct  at  the  close  of  the  paleozoic  epoch.  Euomphalus  is  a  character- 
istic univalve  shell  of  this  period.  In  the  interior  it  is  often  divided  into 
chambers  (fig.  527  d),  the  septa  or  partitions  not  being  perforated  as  in 


Fig.  527. 


Euomphalus  pentagulattit,  Sowerby.    Mountain  Limestone. 
a,  Upper  side ;  &,  lower,  or  umbilical  side ;  c,  view  showing  mouth,  which 
is  less  pentagonal  in  older  individuals ;  d,  view  of  polished  section,  showing 
internal  chambers. 

foraminiferous  shells,  or  in    those  having  siphuncles,  like  the  Nautilus. 
The  animal  appears  to  have  retreated  at  different  periods  of  its  growth 
from  the   internal  cavity   previously  formed,   and  to   have   closed  all 
communication  with  it  by  a  septum.    The  number 
of  chambers  is  irregular,  and  they  are  generally 
wanting  in  the  innermost  whorl.    The  animal  of 
the  recent  Turritella  communis  partitions  off  in 
like  manner  as  it  advances  in  age  a  part  of  its 
spire,  forming  a  shelly  septum. 

Nearly  20    species  of  the   genus  Bellerophon 
(see  fig.  528),  a  shell  without  chambers  like  the 
living  Argonaut,  occur  in   the  Mountain  Lime-  £eiierophon<x>8tatus,Sow. 
stone.     The  genus  is  not  met  with  in  strata  of 


Mountain  Limestone. 


4u8  FOSSILS  OF  MOUNTAIN  LIMESTONE.  [On.  XXV. 

later  date.  It  is  most  generally  regarded  as  belonging  to  the  Heteropoda, 
and  allied  to  the  Glass-Shell,  Carinaria  •  but  by  some  few  it  is  thought 
to  be  a  simple  form  of  Cephalopod. 

The  carboniferous  Cephalopoda  do  not  depart  so  widely  from  the  living 
type  (the  Nautilus),  as  do  the  more  ancient  Silurian  representatives  of 
the  same  order ;  yet  they  offer  some  remarkable  forms  scarcely  known  in 
strata  newer  than  the  coal.  Among  these  is  Orthoceras,  a  siphuncled 
and  chambered  shell,  like  a  Nautilus  uncoiled  and  straightened  (fig.  529). 
Some  species  of  this  genus  are  several  feet  long.  The  Goniatite  is  another 

Fig.  529. 


Portion  of  Orthoceras  laterale,  Phillips.    Mountain  Limestone. 

genus,  nearly  allied  to  the  Ammonite,  from  which  it  differs  in  having  the 
lobes  of  the  septa  free  from  lateral  denticulations,  or  crenatures  ;  so  that 
the  outline  of  these  is  continuous  and  uninterrupted. 

The  species  represented  in  fig.  530  is  found  in  almost  all  localities,  and 
presents  the  zigzag  character  of  the  septal  lobes  in  perfection. 

In  another  species  (fig.  531),  the  septa  are  but  slightly  waved,  and  sc 
approach  nearer  to  the  form  of  those  of  the  Nautilus.  The  dorsal  position 

Fig.  530.  Fig.  531. 


Goniatites  crenistria,  Phill.    Mountain  Goniatites  cvolutus,  Phillips. 

Limestone.      N.  America ;    Britain  ;  Mountain  Limestone. 

Germany,  &c.  Yorkshire. 

a.  Lateral  view. 

&.  Front  view,  showing  the  mouth. 

of  the  siphuncle,  however,  clearly  distinguishes  the  Goniatite  from  the 
Nautilus,  and  proves  it  to  have  belonged  to  the  family  of  the  Ammonites, 
from  which,  indeed,  some  authors  do  not  believe  it  to  be  generically  distinct. 
Fossil  fish. — The  distribution  of  these  is  singularly  partial ;  so  much 
so,  that  M.  de  Koninck  of  Liege,  the  eminent  paleontologist,  once  stated 
to  me  that,  in  making  his  extensive  collection  of  the  fossils  of  the  Moun- 
tain Limestone  of  Belgium,  he  had  found  no  more  than  four  or  five  ex- 
amples of  the  bones  or  teeth  of  fishes.  Judging  from  Belgian  data,  he 
might  have  concluded  that  this  class  of  vertebrata  was  of  extreme  rarity 
in  the  carboniferous  seas  ;  whereas  the  investigation  of  other  coun- 
tries has  led  to  quite  a  different  result.  Thus,  near  Clifton,  on  the  Avon, 


OH.  XXV.] 


LOWER   CARBONIFEROUS  STRATA. 


409 


there  is  a  celebrated  "  bone  bed,"  almost  entirely  made  up  of  ichthyolites ; 
and  the  same  may  be  said  of  the  "  fish-beds"  of  Armagh,  in  Ireland.  They 
consist  chiefly  of  the  teeth  of  fishes  of  the  Placoid  order,  nearly  all  of 
them  rolled  as  if  drifted  from  a  distance.  Some  teeth  are  sharp  and 
pointed,  as  in  ordinary  sharks,  of  which  the  genus  Cladodus  affords  an 
illustration ;  but  the  majority,  as  in  Psammodus  and  Cochliodus,  are, 
like  the  teeth  of  the  Cestracion  of  Port  Jackson  (see  above,  fig.  288,  p. 
249),  massive  palatal  teeth  fitted  for  grinding.  (See  figs.  532,  533.) 


Fig.  582. 


Fig.  533. 


Psammodu*  porosus,  Agas.    Bone-bed,  Mountain 
Limestone.    Bristol;  Armagh. 


Cochliodits  contortus,  Agas.  Bone-bed, 
Mountain  Limestone.  Bristol;  Ar- 
magh. 


There  are  upwards  of  70  other  species  of  fish-remains  known  in  the 
Mountain  Limestone  of  the  British  Islands.  The  defensive  fin-bones  of 
these  creatures  are  not  unfrequent  at  Armagh  and  Bristol  ;  those  known 
as  Oracanthus  are  often  of  a  very  large  size.  Ganoid  fish,  such  as 
Holoptychius,  also  occur  ;  but  these  are  far  less  numerous.  The  great 
Meyalichthys  Hibberti  appears  to  range  from  the  Upper  Coal-measures 
to  the  lowest  Carboniferous  strata. 

Foraminifera.  —  This  somewhat  important  group  of  the  lower  animals, 
which  is  represented  so  fully  at  later  epochs  by  the  Nummulites  and 
their  numerous  minute  allies,  appears  in  the  Mountain  Limestone  to  be 
restricted  to  a  very  few  species,  the  individuals,  however,  of  which  are 
vastly  numerous.  Textularia,  Nodosaria,  Endothyra, 
and  Fusulina  (fig.  534),  have  been  recognized.  The 
first  two  genera  are  common  to  this  and  all  the  after 
periods  ;  the  third  has  already  appeared  in  the  Upper 
Silurian,  but  is  not  known  above  the  Carboniferous  ;  Magnified  3  diam. 
the  fourth  (fig.  534)  is  peculiar  to  the  Mountain  Lime-  MoQntain  Limestone. 
stone,  and  is  characteristic  of  the  formation  in  the  United  States,  Russia. 
and  Asia  Minor. 


Fie.  534 


STRATA  CONTEMPORANEOUS  WITH  THE  MOUNTAIN  LIMESTONE. 

In  countries  where  limestone  does  not  form  the  principal  part  of  the 
Lower  Carboniferous  series,  this  formation  assumes  a  very  different  char- 
acter, as  in  the  Rhenish  Provinces  of  Prussia,  and  in  the  Hartz.  The 
slates  and  sandstones  called  Kiesel-schiefer  and  Younger  Greywacke 
(Jungere  grauwacke)  by  the  Germans,  were  formerly  referred  to  the 
Devonian  group,  but  are  now  ascertained  to  belong  to  the  "  Lower  Car- 


410        CAKBONIFEROUS  LIMESTONE  OF  N.  AMEEICA.     [Cu.  XXV 

boniferous."  The  prevailing  shell  which  characterizes  the  carbonaceous 
schists  of  this  series,  both  on  the  Continent  and  in  England,  is  Posido- 
nomya  Becheri  (fig.  535).  Some  well- 
known  mountain-limestone  species,  such 
as  Goniatites  crenistria  (see  fig.  530) 
and  6r.  reticulatus,  also  occur  in  the 
Hartz.  In  the  associated  sandstones  of 
the  same  region,  fossil  plants,  such  as 
Lepidodendron  and  the  allied  genus 
Saginaria,  are  common;  also  Knorria, 
Calamites  Suclcovii,  and  C.  transi- 
tionis,  Gopp.,  some  peculiar,  others  spe- 
cifically identical  with  ordinary  coal-measure  fossils.  The  true  geological 
position  of  these  rocks  in  the  Hartz  was  first  determined  by  MM.  Murchi- 
son  and  Sedgvvick  in  1840.* 

CARBONIFEROUS  LIMESTONE  IN  NORTH  AMERICA. 

The  coal-measures  of  Nova  Scotia  have  been  described  (p.  377).  The 
lower  division  contains,  besides  large  stratified  masses  of  gypsum,  some 
bands  of  marine  limestone  almost  entirely  made  up  of  encrinites,  and,  in 
some  places,  containing  shells  of  genera  common  to  the  mountain  lime- 
stone of  Europe. 

In  the  United  States  the  carboniferous  limestone  underlies  the  pro- 
ductive coal-measures  ;  and,  although  very  inconspicuous  on  the  margin 
of  the  Alleghany  or  Great  Appalachian  coal-field  in  Pennsylvania,  it  ex- 
pands in  Virginia  and  Tennessee.  Its  still  greater  extent  and  importance 
in  the  Western  or  Mississippi  coal-fields,  in  Kentucky,  Indiana,  Iowa, 
Missouri,  and  other  western  states,  has  been  well  shown  by  Dr.  D.  D. 
Owen.  In  those  regionsf  it  is  about  400  feet  thick,  and  abounds,  as  in 
Europe,  in  shells  of  the  genera  Productus  and  Spirifer,  with  Pentremitcs 
and  other  crinoids  and  corals.  Among  the  latter,  Lithostrotion  basalti- 
forme  or  striatum  (fig.  516,  p.  404),  or  a  closely-allied  species,  is  common. 

*  Trans.  Geol.  Soc.  London,  2d  series,  vol.  yi.  p.  228. 
f  Owen's  Geol.  Survey  of  Wisconsin,  <fec,  1852. 


CH.  XXVL]  OLD  BED  SANDSTONE. 


CHAPTER  XXVL 

OLD  RED  SANDSTONE,  OR  DEVONIAN  GROUP. 

Old  Red  Sandstone  of  the  Borders  of  "Wales — Of  Scotland  and  the  Sonth  of 
Ireland — Foseil  reptile  and  foot-tracks  at  Elgin — Fossil  Devonian  plants  at 
Kilkenny — Ichthyolites  of  Clashbinnie — Fossil  fish,  crustaceans,  <fec.,  of  Caith- 
ness and  Forfarshire — Distinct  lithological  type  of  Old  Red  in  Devon  and 
Cornwall — Term  Devonian — Organic  remains  of  intermediate  character  be- 
tween those  of  the  Carboniferous  and  Silurian  systems — Devonian  series  of 
England  and  the  Continent — Upper  Devonian  rocks  and  fossils — Middle — 
Lower — Old  Red  Sandstone  of  Russia — Devonian  strata  of  the  United  States — 
Coral-reefs  at  the  Falls  of  the  Ohio. 

IT  has  been  already  shown  in  the  section  (p.  332),  that  the  carbonifer- 
ous strata  are  surmounted  by  a  system  called  "  The  New  Red,"  and  un- 
derlaid by  another  termed  the  "  Old  Red  Sandstone."  The  last-mentioned 
group  acquired  this  name  because  in  Herefordshire  and  Scotland,  where 
it  was  originally  studied,  it  consisted  chiefly  of  red  sandstone,  shale,  and 
conglomerate.  It  was  afterwards  termed  "  Devonian,"  for  reasons  which 
will  be  explained  in  the  sequel.  For  many  years  it  was  regarded  as  very 
barren  of  organic  remains ;  and  such  is  undoubtedly  its  character  over 
very  wide  areas  where  calcareous  matter  is  wanting,  and  where  its  color 
is  determined  by  the  red  oxide  of  iron. 

"  Old  Red "  in  Herefordshire,  &c. — In  Herefordshire,  Worcestershire, 
Shropshire,  and  South  Wales,  this  formation  attains  a  great  thickness, 
sometimes  between  8,000  and  10,000  feet.  In  these  regions,  it  has  been 
subdivided  into 

1st.  Conglomerate,  passing  downwards  into  chocolate-red  and  green 
sandstone  and  marl. 

2d.  Marl  and  cornstone, — red  and  green  argillaceous  spotted  marls, 
with  irregular  courses  of  impure  concretionary  limestone,  provincially 
called  Cornstone,  and  some  beds  of  white  sandstone.  In  the  cornstones, 
and  in  those  flagstones  and  marls  through  which  calcareous  matter  is 
most  diffused,  some  remains  of  fishes  of  the  genera  Onchus  and  Cepha- 
laspis  occur.  Several  specimens  of  the  latter  have  been  traced  to  the 
lowest  beds  of  the  "  Old  Red,"  in  May  Hill,  in  Gloucestershire,  by  Sir 
R.  Murchison  and  Mr.  Strickland.* 

Old  Red  Sandstone  of  Scotland  and  Ireland. — South  of  the  Gram- 
pians, in  Forfarshire,  Kincardineshire,  and  Fife,  the  Old  Red  Sandstone 
may  be  divided  into  three  groups. 

*  Murchison's  Siluria,  p.  245. 


412  FOSSIL  EEPTILE   OF   OLD  RED   SANDSTONE.       [Ca  XXVI. 


Fig.  536. 


A.  Yellow  sandstone,  with  some  bands  of  white  sandstone. 

B.  Red  shale,  sandstone  with  cornstone,  and  at  the  base  a  conglomer- 

ate (Nos.  1,  2,  &  3  Section,  p.  48). 

C.  Roofing  and  paving  stone,  highly  micaceous,  and  containing  a  slight 

admixture  of  carbonate  of  lime  (No.  4,  p.  48). 

The  upper  member,  or  yellow  sandstone,  A,  is  seen  at  Dura  Den,  near 
Cupar,  in  Fife,  immediately  underlying  the  coal.  It  consists  of  a  yellow 
sandstone  in  which  fish  of  the  genera  Pterichthys  (for  genus  see  fig.  550), 
Pamphractus,  Glyptopomus,  Holoptychius,  and  others  abound. 

On  the  south  side  of  the  Moray  Firth,  near  Elgin,  certain  yellow 
and  white  sandstones  were  classed  long  since  by  Professor  Sedgwick 
and  Sir  R.  Murchison  as  the  uppermost  beds  of  the  "  Old  Red ;"  and 
they  are  generally  regarded  as  the  equivalent  of  the  Yellow  Sandstone 
of  Fife  above  alluded  to.  They  contain  large  rhombcidal  scales  of  a 
fish  called  by  Agassiz  Stayonolepis  Robertsoni,  and  referred  by  him  to 
the  Dipterian  family.  This  family,  ob- 
serves Mr.  Hugh  Miller,  is  emphati- 
cally characteristic  of  the  Old  Red 
Sandstone.  The  scales  of  this  Sta- 
gonolepis,  the  only  parts  of  the  species 
yet  known,  are  so  like  those  of  Glyp- 
topomus in  form  and  pattern  that  they 
may  possibly  prove  to  be  referable  to 
the  same  genus.  The  Glyptopomus ',  as 
we  have  seen,  is  found  in  the  yellow 
sandstone  of  Dura  Den  in  Fife,  and  the 
genus  has  not  hitherto  been  met  with 
in  any  formation  except  the  Devonian. 

The  light-colored  sandstone  of 
Morayshire  passes  down  into  a  con- 
formable series  of  strata,  which  are 
full  of  undoubted  "  Old  Red"  fossils. 
I  have  dwelt  thus  particularly  on  the 
age  of  this  rock,  because  it  has  yielded 
recently  (1851)  the  bones  of  a  reptile, 
the  first  and  only  memorials  of  that 
class  yet  discovered  in  a  stratum  of 
such  high  antiquity.  This  fossil  was 
obtained  by  Mr.  Patrick  Duff,  author 
of  a  "  Sketch  of  the  Geology  of 
Morayshire,"  from  a  quarry  at  Cum- 
mingstone,  near  Elgin.  The  skeleton 
represented  in  the  annexed  figure 
(fig.  536),  is  41  inches  in  length,  but 
part  of  the  tail  is  concealed  in  the 
rock ;  and,  if  the  whole  were  visible, 
it  might  be  more  than  6  inches  long. 


Telerpeton  Elginetise.    (Mantell.) 
Natural  size. 


Eeptile  in  the  Old  Eed  Sandstone,  from 
near  Elgin,  Morayshire. 


Ca.  XXVL]         FOSSIL  FOOTPRINTS  OF   "  OLD  RED.' 


413 


The  matrix  is  a  fine-grained  whitish  sandstone,  with  a  cement  of  carbon- 
ate of  lime.  Although  almost  all  the  bones  except  those  of  the  skull 
have  decomposed,  their  natural  position  can  still  be  seen.  '  Nearly  perfect 
casts  of  their  form  were  taken  by  Dr.  Mantell  from  the  hollow  moulds 
which  they  have  left  in  the  rock. 

Slight  indications  are  visible  of  minute  conical  teeth.  Of  ribs  there 
are  twenty-four  pairs,  very  short  and  slender.  The  pelvis  is  placed  after 
the  twenty-fourth  vertebra,  precisely  as  in  the  living  Iguana.  On  the 
whole,  Dr.  Mantell  inferred  that  the  animal  possessed  many  Lacertian 
characters  blended  with  those  of  the  Batrachians.  He  was  unable  to 
decide  whether  it  was  a  small  terrestrial  lizard,  or  a  freshwater  Batrachian, 
resembling  the  Tritons  and  aquatic  Salamanders. 

Although  this  fossil  is  the  most  ancient  quadruped  of  which  any 
osseous  remains  have  yet  been  brought  to  light,  it  seems  not  to  have 
been  the  only  one  then  existing  in  that  region,  for  Captain  Brickenden 
observed,  in  1850,  on  a  slab  of  sandstone  from  the  same  quarry  at  Cum- 
mingstone,  a  continuous  series  of  no  less  than  thirty-four  footprints  of  a 
quadruped.  A  small  part  of  this  track,  the  course  of  which  is  supposed 
to  have  been  from  A  to  B,  is  represented  in  the  annexed  cut  (fig.  537). 
The  footprints  are  in  pairs,  forming  two  parallel  rows  ;  the  hind  foot  being 

Fig.  537. 


Scale  one-sixth  the  original  size. 

Part  of  the  trail  of  a  (Chelonian  ?)  quadruped  from  the  Old  Red  Sandstone  of  Cum- 
mingstone,  near  Elgin,  Morayshire.— Captain  Brickenden. 

one  inch  in  diameter,  and  larger  than  the  fore  foot  in  the  proportion  of  4 
to  3.  The  stride  must  have  been  about  4  inches.  The  impressions  re- 
semble those  left  by  a  tortoise  walking  on  sand  ;  and,  if  this  be  the  'true 
interpretation  of  the  trail,  they  are  the  only  indications  as  yet  known  of  a 
chelonian  more  ancient  than  the  trias. 

I  have  already  alluded  (p.  400)  to  trails  referred  by  American  geolo- 
gists to  several  species  of  air-breathing  reptiles,  and  discovered  on  the 
eastern  flank  of  the  Alleghany  range,  in  Pennsylvania,  in  a  red  shale,  so 
ancient  that  a  question  has  arisen  whether  the  rock  should  be  classed  as 
the  lowest  member  of  the  carboniferous,  as  Professor  H.  D.  Rogers  con- 
ceives, or  as  the  uppermost  Devonian,  as  some  have  contended  (see  p.  400). 
They  at  least  demonstrate  that  certain  quadrupeds,  of  larger  size  than 
any  of  the  bones  that  have  been  found  in  carboniferous  rocks,  existed  at 


4:14: 


FOSSILS  OF  THE 


[CH.  XXVI. 


the  time  when  the  ancient  Red  Shale,  usually  termed,  in  the  United 
States,  "  infra-carboniferous,"  was  in  the  course  of  deposition. 

In  Ireland,  the  upper  beds  of  the  Old  Red  or  yellow  sandstone  of 
Kilkenny  contain  fish  of  the  genera  Coccosteus  and  Dendrodus,  charac- 
teristic forms  of  this  period,  together  with  plants  specifically  distinct 
from  any  known  in  the  coal-measures,  but  referable  to  the  genera  found 
in  them ;  as,  for  example,  Lepidodendron  and  Cyclopteris  (see  figs.  538 
and  539).  The  sterns  of  the  latter  have,  in  some  specimens,  broad  bases 
of  attachment,  and  may  therefore  have  been  tree-ferns. 


Fig.  588. 


Fig.  539. 


Stem  of  Lepidodendron,  so  compressed  as 
to  destroy  the  quincunx  arrangement  of 
the  scars.  Upper  Devonian,  Kilkenny. 


Cyclopteris  Ifibernica,  Forbes. 
Upper  Devonian,  Kilkenny. 


In  the  same  strata  shells  having  the  form  of  the  genus  Anodon,  and 
which  probably  belonged  to  freshwater  testacea,  occur.  Some  geologists, 
it  is  true,  still  doubt  whether  these  beds  ought  not  rather  to  be  classed 
as  the  lowest  beds  of  the  carboniferous  series,  together  with  the  yellow 
sandstone  of  Mr.  Griffiths  (see  p.  359) ;  but  the  associated  ichthy elites 
and  the  distinct  specific  character  of  the  plants,  seem  to  favor  the  opinion 
above  expressed. 

B.  (Table,  p.  412.) — We  come  next  to  the  middle  division  of  the 
"  Old  Red,"  as  exhibited  south  of  the  Grampians,  and  consisting  of — 1st, 
red  shale  and  sandstone,  with  some  cornstone,  occupying  the  Valley  of 
Strathmore,  in  its  course  from  Stonehaven  to  the  Firth  of  Clyde ;  and, 
Fi    54Q  2dly,  of  a  conglomerate,  seen  both  at 

the  foot  of  the  Grampians,  a-nd  on  the 
flanks  of  the  Sidlaw  Hills,  as  shown  in 
the  section  at  p.  48,  Nos.  1,  2,  and  3. 
In  the  uppermost  part  of  the  divi- 
sion No.  1,  or  in  the  beds  which, 
in  Fife,  underlie  the  yellow  sand- 
stone, the  scales  of  a  large  ganoid 
fish,  of  the  genus  Holoptychius,  were 
first  observed  by  Dr.  Fleming,  at 
Clashbinnie,  near  Perth ;  and  an  en- 
tire specimen,  more  than  2  feet  in 
length,  was  afterwards  found  by  Mr. 

Scab  of  Holopiyehius  nobihwmus,  Agas.  ' 

Clashbinnie.    Nat.  size.  Noble.     Some  of  these  scales  (see  ng. 

540)  measured  3  inches  in  length,  and  2£  in  breadth. 


^mamy\i 


CH.  XXVI.] 


OLD   EED   SANDSTONE . 


415 


C.  (Table,  p.  412). — The  third  or  lowest  division  south  of  the  Gram- 
pians consists  of  gray  paving-stone  and  roofing-slate,  with  associated  red 
and  gray  shales  ;  these  strata  underlie  a  dense  mass  of  conglomerate.  In 
these  gray  beds  several  remarkable  fish  have  been  found  of  the  genus 
named  by  Agassiz  Cephalaspis,  or  "  buckler-headed,"  from  the  extraor- 
dinary shield  which  covers  the  head  (see  fig.  541),  and  which  has  often 
been  mistaken  for  that  of  a  trilobite,  such  as  Asaphus. 

Fig.  541. 


Cephala&pis  Lyettii,  Agass.    Length  6|  inches. 
From  a  specimen  in  my  collection  found  at  Glammiss,  in  Forfarshire ;  see  other  figures, 

Agassiz,  vol.  ii.  tab.  1  a,  and  1  6. 
a.  One  of  the  peculiar  scales  with  which  the  head  is  covered  when  perfect    These  scales 

are  generally  removed,  as  in  the  specimen  above  figured. 
6,  c.  Scales  from  different  parts  of  the  body  and  tail 

In  the  same  rock  at  Carmylie,  in  Forfarshire,  commonly  known  as  the 
Arbroath  paving-stone,  fragments  of  a  huge  crustacean  have  been  met 
with  from  time  to  time.  They  are  called  by  the  Scotch  quarrymen  the 
"  Seraphim,"  from  the  wing-like  form  and  feather-like  ornament  of  the 
hinder  part  of  the  head,  the  part  most  usually  met  with.  Agassiz,  having 


Fig.  542. 


Portions  of  the  Pterygotus  anglicus,  Agassiz. 

1.  Middle  portion  of  the  "  Seraphim"  or  back  of  the  head,  with  the  scale-like  sculpturing. 

2.  Portion  of  the  dilated  base  of  one  of  the  anterior  feet,  with  its  strong  spines  or  teeth, 

used  as  masticating  organs. 

8.  The  proximal  portion  of  one  of  the  great  anterior  clnws. 

4.  Termination  of  the  same,  with  the  serrated  pincers.   (See  Agass.  Poiss.  Foss.  du  Yienx 
Gres  Eouge,  plate  A.) 

1  and  2  are  of  the  natural  size ;  3  and  4  are  reduced  one  half. 


416 


FOSSILS  OF  THE 


[Cn.  XXVI. 


Fig.  548. 


previously  referred  some  of  these  fragments  to  the  class  of  fishes,  was  the 
first  to  recognize  their  true  nature,  and  in  the  first  plate  of  his  "  Poissons 
Fossiles  du  Vieux  Gres  Rouge,"  he  figured  the  portions  on  which  he 
founded  his  opinion. 

The  carapace  of  this  huge  crustacean,  which  must  have  rivalled,  if  not 
exceeded  in  size  the  largest  crabs,  is  furnished  at  its  hinder  part  with 
short  prongs,  and  has  two  large  eyes  near  the  middle,  much  like  those  of 
the  Eurypterus  found  in  the  coal  formation  of  Glasgow.  The  body  con- 
sists of  ten  or  eleven  movable  rings 
(the  exact  number  is  not  ascer- 
tained), and  was  terminated  by  an 
oval-pointed  tail.  The  whole  sur- 
face is  covered  by  the  scale-like 
markings  before  mentioned  as  or- 
namenting the  head.  Prof.  M'Coy, 
to  whom  I  owe  these  notes  on  the 
general  structure,  has  kindly  fur- 
nished me  with  a  restoration  of  the 
entire  animal  (fig.  543),  which  he 
believes  to  be  closely  allied  to  the 
great  Eurypterus  before  mentioned, 
if  not  of  the  very  same  genus,  and, 
moreover,  of  the  same  family  as  the 
living  King-crab  or  Limulus. 

Sir  R.  Murchison  has  expressed 
some  doubts*  whether  the  gray 
beds  of  Forfarshire,  containing  the 
Pterygotus,  may  not  be  referable  to  the  Upper  Silurian  or  Upper  Ludlow 
beds ;  but,  as  they  are  associated  at  Balrudderie  with  numerous  speci- 
mens of  Cephalaspis  (the  bony  bucklers  or  head-pieces  alone  being  pre- 
served), apparently  belonging  to  two  species,  I  think  it  far  more  probable 
that  they  constitute  a  division  of  the  "  Old  Red,"  and  perhaps  not  so  an- 
cient a  one  as  the  bituminous  schists  (6,  p.  418)  in  the  North  of  Scotland. 

In  the  same  gray  paving-stones  and  coarse  roofing-slates  in  which  the 
Cephalaspis  and  Pterygotus  occur,  in  Forfarshire  and  Kincardineshire,  the 
remains  of  grass-like  plants  abound  in  such  numbers  as  to  be  useful  to  the 
geologist  by  enabling  him  to  identify  corresponding  strata  at  distant  points. 
Whether  these  be  fucoids,  as  I  formerly  conjectured,  or  freshwater  plants 
of  the  family  Fluviales,  as  some  botanists  suggest,  cannot  yet  be  deter- 
mined. They  are  often  accompanied  by  fossils,  called  "  berries"  by  the 
quarrymen,  and  which  are  not  unlike  the  form  which  a  compressed 
blackberry  or  raspberry  might  assume  (see  figs.  544  and  545).  Some 
of  these  were  first  observed  in  the  year  1828,  in  gray  sandstone  of  the 
same  age  as  that  of  Forfarshire,  at  Parkhill  near  Newburgh,  in  the  north 
of  Fife,  by  Dr.  Fleming.  I  afterwards  found  them  on  the  north  side  of 
Strathmore,  in  the  vertical  shale  beneath  the  conglomerate,  and  in  the 
*  Siluria,  p.  247. 


Pterygotus  problematicus,  Agassiz. 
Kestoration  by  Professor  M'Coy. 


CH.  XXVL] 


OLD   EED  SANDSTONE. 


417 


same  beds  in  the  Sidlaw  Hills,  at  all  the  points  where  fig.  4  is  introduced 
in  the  section,  p.  48. 


Fig.  544. 


Fig.  545. 


Parka  decipiens,  Fleming. 

In  sandstone  of  lower  beds 
of  Old  Red,  Ley's  Mill, 
Forfarshire. 


Parka  decipiens,  Fleming. 
In  shale  of  lower  beds  of  Old  Eed,  Fife. 


Fig.  546. 


Dr.  Fleming  has  compared  these  fossils  to  the  panicles  of  a  Jurtcus,  or 
the  catkins  of  Sparganiurn,  or  some  allied  plant,  and  he  was  confirmed  in 
this  opinion  by  finding  a  specimen  at  Balrudderie,  showing  the  undei 
surface  smoother  than  the  upper,  and  displaying  what 
may  be  the  place  of  attachment  of  a  stalk.    I  have  met 
with  some  specimens  in  Forfarshire  imbedded  in  sand- 
stone, and  not  associated  with  the  leaves  of  plants  (see 
fig.  544),  which  bore  a  considerable  resesemblance  to 
the  spawn  of  a  recent  Natica  (fig.  546),  in  which  the 
eggs  are  arranged  in  a  thin  layer  of  sand,  and  seem  to 
have  acquired  a  polygonal  form  by  pressing  against 
each  other ;  but,  as  no  gasteropodous  shells  have  been 
detected  in  the  same  formation,  the  Parka  has  probably  no  connection 
with  this  class  of  organisms. 

The  late  Dr.  Mantell  was  so  much  struck  with  the  resemblance  of  one 


Fig.  547. 


Fig.  543. 


Fossil— Old  Eed. 

Fig.  549. 


Eecent 


Fig.  547.  Slab  of  Old  Eed  Sandstone,  -» 
Forfarshire,  with  bodies  like  the    _• 
ova  of  Batrachians.  J.  f 

a.  Ova  ?  in  a  carbonized  state.     I  & 
6.  Egg-cells  ?,  the  ova  shed.        J 
Fig.  548.  Eggs  of  the  common  frog, 
liana  temporaria,  in  a  carbon- 
ized state,  from  a  dried-up  pond  in 
Clapham  Common. 

a.  The  ova. 

b.  A  transverse  section  of  the    p 

mass  exhibiting  the  form  of 
the  egg-cells. 


Fig.  549.  Shale  of  Old  Eed  Sandstone,  or 
Devonian,  Forfarshire,  with  impression 
of  plants  and  eggs  of  Batrachians  ? 
a.  Two   pair   of  ova?    resembling 
those  of  large  Salamanders  01 
Tritons— on  the  same  leaf 
6,  5.  Detached  ova? 
c.  Egg-cells  (?)  of  frogs  or  Ranina. 


418  OLD  EED   OF  NOETH  OF  SCOTLAND.          [Cm  XXVI 

of  my  specimens  (see  fig.  547)  to  a  small  bundle  of  the  dried-up  eggs  of 
the  common  English  frog,  which  he  had  obtained  in  a  black  and  car- 
bonaceous state  (see  fig.  548)  from  the  mud  of  a  pond  near  London,  that 
he  suggested  a  batrachian  origin  for  the  fossil ;  and  Mr.  Newport  con- 
curred in  the  idea,  adding  that  other  larger  and  more  circular  fossils  (fig. 
549),  which  I  procured  from  shale  in  the  same  "  Old  Red,"  occurring 
singly  or  in  pairs,  and  attached  to  the  leaves  of  plants,  might  possibly  be 
the  ova  of  some  gigantic  triton  or  salamander. 

The  general  absence  of  reptilian  remains  from  strata  of  the  Devonian 
period  will  weigh  strongly  with  many  geologists  against  such  conjectures. 

"  Old  Red"  in  the  North  of  Scotland.— The  whole  of  the  northern  part 
of  Scotland,  from  Cape  Wrath  to  the  southern  flank  of  the  Grampians,  has 
been  well  described  by  Mr.  Hugh  Miller  as  consisting  of  a  nucleus  of 
granite,  gneiss,  and  other  hypogene  rocks,  which  seem  as  if  set  in  a  sand- 
stone frame.*  The  beds  of  the  Old  Red  Sandstone  constituting  this  frame 
may  once  perhaps  have  extended  continuously  over  the  entire  Grampians 
before  the  upheaval  of  that  mountain  range  ;  for  one  band  of  the  sand- 
stone follows  the  course  of  the  Moray  Frith  far  into  the  interior  of  the 
great  Caledonian  valley,  and  detached  hills  and  island-like  patches  occur 
in  several  parts  of  the  interior,  capping  some  of  the  higher  summits  in 
Sutherlandshire,  and  appearing  in  Morayshire  like  oases  among  the  granite 
rocks  of  Strathspey.  On  the  western  coast  of  Ross-shire,  the  Old  Red 
forms  those  three  immense  insulated  hills  before  described  (p.  67),  where 
beds  of  horizontal  sandstone,  3000  feet  high,  rest  unconformably  on  a  base 
of  gneiss,  attesting  the  vast  denudation  which  has  taken  place. 

As  the  mineral  character  of  the  "  Old  Red"  north  of  the  Grampians 
differs  considerably  from  that  of  the  south,  especially  in  the  middle  and 
lower  divisions,  I  shall  now  allude  to  it  separately.  The  upper  portion, 
consisting  of  light-colored  sandstones,  and  containing  the  Telerpeton  of 
Elgin,  has  been  already  classed,  A.,  p.  412,  as  the  equivalent  of  the  yel- 
low sandstone  of  Fife.  That  upper  member  passes  downwards  into  red 
and  variegated  sandstone  and  conglomerate,  which  may  correspond  with 
the  beds  called  B.,  in  the  same  section  at  p.  412.  To  the  above  succeeds, 
in  the  descending  order,  "  the  middle  formation"  of  Mr.  Hugh  Miller,  com- 
posed of  thin,  fissile,  gray  sandstone,  in  which,  in  Morayshire,  Dr.  Malcolm- 
son  found  a  species  of  Ccphalaspis  ;  but  whether  these  beds  are  of  the 
age  of  the  paving-stone  of  Arbroath  (C.  Table,  p.  412)  is  as  yet  uncertain. 

Next  below  is  the  "  inferior  division"  of  Hugh  Miller,  comprising — 

a.  Red  and  variegated  sandstones. 

b.  Bituminous  schists. 

c.  Coarse  sandstone. 

d.  Great  conglomerate. 

In  the  schists  5,  a  great  variety  of  fish  are  met  with  in  the  counties  01 
Banff,  Nairn,  Moray,  Cromarty,  and  Caithness,  and  also  in  Orkney,  be- 
longing to  the  genera  Pterichthys  (fig.  550),   Coccosteus,  Diplopterus, 
Dipterus,  Cheiracanthus,  Asterolepis,  and  others  described  by  Agassiz. 
*  "  Old  Red  Sandstone,"  1841. 


'OH.  XXVL] 


TERM   "  DEVONIAN." 


419 


Pterichthys,  Agassiz ;  upper  side,  showing 
mouth ;  as  restored  by  H.  Miller.* 


Five  species  of  Ptericlitliys  have  been  found  in  this  lowest  divi- 
sion of  the  Old  Red.  The  wing- 
like  appendages,  whence  the 
genus  is  named,  were  first  sup- 
posed by  Mr.  Miller  to  be  pad- 
dles, like  those  of  the  turtle ;  but 
Agassiz  regards  them  as  weapons 
of  defence,  like  the  occipital 
spines  of  the  River  Bull-head 
( Coitus  gobio,  Linn.) ;  and  con- 
siders the  tail  to  have  been  the 
only  organ  of  motion.  The  ge- 
nera Dipterus  and  Diplopterus 
are  so  named,  because  their  two 
dorsal  fins  are  so  placed  as  to 
front  the  anal  and  ventral  fins, 
so  as  to  appear  like  two  pair  of 
wings.  They  have  bony  enamelled  scales. 

The  Asterolepis  was  a  ganoid  fish  of  gigantic  dimensions.  A.  Asmusii, 
Eichwald,  the  species  characteristic  of  the  Old  Red  Sandstone  of  Russia 
as  well  as  that  of  Scotland,  attained  the  leDgth  of  between  20  and  30 
feet.  It  was  clothed  with  strong  bony  armor,  embossed  with  star-like 
tubercles,  but  it  had  only  a  cartilaginous  skeleton.  The  mouth  was 
furnished  with  two  rows  of  teeth,  the  outer  ones  small  and  fish-like,  the 
inner  larger  and  with  a  reptilian  character.f  The  Asterolepis  oocurs  also 
in  the  Devonian  rocks  of  North  America,  in  the  lower  division  of  the 
Old  Red.  Coniferous  wood,  with  structure  showing  medullary  rays,  has 
likewise  been  detected  in  the  lower  division  by  Hugh  Miller,|  who  has 
pointedly  dwelt  on  the  importance  of  the  fact,  as  the  oldest  example  yet 
known  of  so  higily  organized  a  plant  occurring  in  a  rock  of  such  antiquity. 
South  Devon  and  Cornwall. — Term  Devonian. — A  great  step  was 
made  in  the  classification  of  the  slaty  and  calciferous  strata  of  South 
Devon  and  Cornwall  in  1837,  when  a  large  portion  of  the  beds,  pre- 
viously referred  to  the  "  transition"  or  Silurian  series,  were  found  to  be- 
long in  reality  to  the  period  of  the  Old  Red  Sandstone.  For  this  reform 
we  are  indebted  to  the  labors  of  Professor  Sedgwick  and  Sir  R.  Murchison, 
assisted  by  a  suggestion  of  Mr.  Lonsdale,  who,  in  1837,  after  examining 
the  South  Devonshire  fossils,  perceived  that  some  of  them  agreed  with 
those  of  the  Carboniferous  group,  others  with  those  of  the  Silurian,  while 
many  could  not  be  assigned  to  either  system,  the  whole  taken  together 
exhibiting  a  peculiar  and  intermediate  character.  But  these  paleonto- 
logical  observations  alone  would  not  have  enabled  us  to  assign,  with  accu- 

*  Old  Red  Sandstone.    Plate  1,  fig.  1.    Mr.  Miller's  description  of  the  fish  is 
most  graphic  and  correct. 

f  Footprints  of  the  Creator,  by  Hugh  Miller, 
j  Footprints,  p.  199. 


420  DEVONIAN"  SERIES.  FCn,  XXVI 

racy,  the  true  place  in  the  geological  series  of  these  slate-rocks  and 
limestones  of  South  Devon,  had  not  Messrs.  Sedgwick  and  Murchison, 
in  1836  and  183 7,  discovered  that  the  culmiferous  or  anthracitic  shales 
of  North  Devon  belonged  to  the  Coal,  and  not,  as  preceding  observers 
had  imagined,  to  the  "  transition  "  period. 

As  the  strata  of  South  Devon  here  alluded  to  are  far  richer  in  organic 
remains  than  the  red  sandstones  of  contemporaneous  date  in  Herefordshire 
and  Scotland,  the  new  name  of  the  "  Devonian  system  "  was  proposed  as 
a  substitute  for  that  of  Old  Red  Sandstone. 

The  link  supplied  by  the  whole  assemblage  of  imbedded  fossils,  con- 
necting as  it  does  the  paleontology  of  the  Silurian  and  Carboniferous 
groups,  is  one  of  the  highest  interest,  and  equally  striking  whether  we 
regard  the  genera  of  the  corals  or  of  the  shells.  The  species  are  mostly 
distinct,  except  in  the  upper  group. 

The  rocks  of  this  group  in  South  Devon  consist,  in  great  part,  of  green 
chloritic  slates,  alternating  with  hard  quartzose  slates  and  sandstones. 
Here  and  there  calcareous  slates  are  interstratified  with  blue  crystalline 
limestone,  and  in  some  divisions  conglomerates,  passing  into  red  sand- 
stone. But  the  whole  series  is  much  altered  and  disturbed  by  the  intru- 
sion of  the  granite  of  Dartmoor  and  other  igneous  rocks. 

In  North  Devon,  on  the  contrary,  the  Devonian  group  has  been  less 
changed,  and  its  relations  to  the  overlying  carboniferous  rocks  or  "  Culm 
Measures"  are  clearly  seen.  The  following  sequence  is  exhibited  in  the 
coast  section  on  the  Bristol  Channel  between  Barnstaple  and  the  North 
Foreland.* 


Upper  - 


Middle^ 


Lower  • 


'T 
u 


Devonian  Series  in  North  Devon, 
a.  Calcareous  brown  slates  ;  with  fossils,  many  of  them  common  to 


1.  •{          the  Carboniferous  grotip.     (Barnstaple,  Pilton,  <fcc.) 

Brown  and  yellow  sandstone,  with  shells  and  land-plants — Stig- 
maria,  Knorria,  and  others.     (Baggy  Point,  Marwood,  &c.) 

2.  Hard  gray  and  reddish  sandstones  and   micaceous  flags,   without 

fossils,  resting  on  soft  greenish  schists  of  considerable  thickness. 
(Morte  Bay,  Bull  Point,  <fcc.) 

3.  Calcareous  slates,  with  eight  or  nine  courses  of  limestone,   full  of 

corals  and  shells  like  those  of  the  Plymouth  limestone.     (Combe 
Martin,  Ilfracombe  Harbor,  &c.) 

4.  Hard,  greenish,  red,  and  purple  sandstones  ;  with  occasional  fossils, 

Spirifers,  <fec.     (Linton,  North  Foreland,  tfcc.) 


5.  Soft  chloritous  slates,  with  some  sandstones ;  Orthis,  Spirifer,   and 
some  Corals.     (Valley  of  Rocks,  Lynmouth,  <fcc.) 

The  successive  beds  of  this  section  have  been  compared  with  those 
of  South  Devon  and  Cornwall,  both  by  the  authors  of  the  "  Devonian  " 
system  and  by  other  observers.  And  Prof.  Sedgwick  has  again  lately 
brought  them  into  closer  comparison.f  Other  geologists,  at  home  and 
abroad,  have  successively  identified  them  with  the  Devonian  series  in 
France,  Belgium,  the  Rhenish  Provincesj  Central  Germany,  and  Amer- 

*  Sedgwick  and  Murchison,  Trans.  Geol.  Soc.,  New  Series,  vol.  v.  p.  644.    De 
la  Bechc,  Geol.  Report,  Devon  and  Cornwall,  pi.  3.     Murchison's  Siluria,  p.  256. 
f  Quart.  Journ.  Geol.  Soc.  vol.  viii.  p.  1,  et  seg. 


CH.  XXVI.] 


UPPER  AND   MIDDLE   DEVONIAN. 


421 


Fig.551. 


ica.*     I  shall  proceed  first  to  treat  of  the  main  divisions  which  have  been 
established  in  Europe. 

Upper  Devonian  Rocks. 

The  slates  and  sandstones  of  Barnstaple  (No.  1,  a,  6  of  the  preceding 
section)  are  represented  in  Cornwall  by  the  limestones  and  slates  of  Pether- 
wyn,  which  rise  in  like  manner  from  under  the  Culm  Measures,  consti- 
tuting the  Petherwyn  group  of  Prof. 
Sedgwick.  These  beds  contain  the 
very  common  Spirifer  disjunctus, 
Sow.  (S.  Verneuilii,  Murch.),  (see 
fig.  551),  a  species  distributed  over 
the  whole  of  Europe,  and  found  even 
in  Asia  Minor  and  China.  Among 
many  other  fossils  the  Clymenia 
linearis  (fig.  552)  and  the  minute 
crustacean  Cypridina  serrato-striata  (fig.  553)  are  so  characteristic  of 
these  upper  beds  in  Belgium,  the  Rhenish  Provinces,  the  Hartz,  Saxony, 

Fig.  552. 


Fig.55a 


Spirifer  di&junctus.  Bow.     8711.  Sp.  Ver- 

neuilii.  March. 
Upper  Devonian,  Boulogne. 


Cypridina  serrato-striata.  Sandberger. 
Weilburg,  &c. ;  Nassau;  Saxony;  Bel- 
gium. 


Clymenia  linearis,  Miinster. 
Petherrpn,  Cornwall ;  Elbersreuth,  Bavaria. 

and  Silesia,  that  strata  of  this  division  in  Germany  are  distinguished  by 
the  names  of  "  Clymenien-Kalk,"  and  "  Cypridinen-schiefer."f 

With  these  are  many  Goniatites  (G.  subsulcatus,  Miinster,  and  other 
species)  both  in  England  and  on  the  continent.  In  Germany  they  are 
usually  confined  to  distinct  beds,  as  at  Oberscheld,  also  at  Couvin  in 
Belgium,  &c.  Trilobites  are  not  unfrequent  in  Cornwall  and  North 
Devon ;  they  are  chiefly  restricted  to  species  of  Phacops  (for  genus,  see 
fig.  585)  ;  but  in  the  upper  Devonian  limestones  of  the  Fichtelgebirge,  as 
at  Elbersreuth  in  Bavaria,  there  are  numerous  genera  and  species  which 
never  rise  higher  in  the  series  or  appear  in  any  portion  of  the  carbonifer- 
ous limestone. 

Middle  Devonian 

The  unfossiliferous  series  (No.  2,  p.  420)  of  North  Devon,  and  the  calca- 
reous beds  of  Ilfracombe  (3),  correspond  to  the  Dartmouth  and  Plymouth 

*  See  Dr.  Fridolin  Sandberger  on  the  Devonian  rocks  of  Nassau  (GeoL  Verhalt. 
Nassau) ;  Fried.  A.  Roemer,  on  the  Hartz  Devonian  Rocks,  in  Dunker  and  Von 
Meyer's  Palaeontographica,  3d  voL  pt  1. 

f  See  Murchison's  Siluria,  chapters  x.  xiv.  and  xv. 


422 


FOSSILS  OF  THE 


[Ca  XXVI 


groups  of  Prof.  Sedgwick's  South  Devon  series,  and  are  the  most  typical 
portion  of  the  Devonian  system.  They  include  the  great  limestones  01 
Plymouth  and  Torbay,  replete  with  shells,  trilobites,  and  corals.  A  thick 
accumulation  of  slate  and  schist,  full  of  the  same  fossils,  occupies  nearly 
all  the  southern  portion  of  Devonshire  and  a  large  part  of  Cornwall. 
Among  the  corals  we  find  the  genera  Favosites,  Heliolites,  and  Cyatho- 
phyllum,  the  last  genus  equally  abundant  in  the  Silurian  and  Carbonifer- 
ous systems,  the  two  former  so  frequent  in  Silurian  rocks.  Some  few 
even  of  the  species  are  common  to  the  Devonian  and  Silurian  groups,  as, 
for  example,  Favosites  polymorpha  (fig.  554),  one  of  the  commonest  of  all 
the  Devonshire  fossils.  The  Cyathophyllum  ccespitosum  (fig.  555)  and 

Fig.  555. 


Fig.  554. 


favoeites  polymorpha,  Goldf.    8.  Devon,  from  a  polished 
specimen. 

a.  Portion  of  the  same  magnified,  to  show  the  pores. 


a.  CyatliophyUum  ccvspitosum, 

Goldf.,  Plymouth. 
&.  A  terminal  star. 
c.  Vertical    section,    exhibiting 

transverse  plates,  and  part  of 

another  hranch. 


Heliolites  pyriformis  (fig.  556)  are  peculiarly  characteristic ;  as  is  another 
very  common  species,  the  Aulopora  serpens  (fig.  557),  which  creeps  over 
corals  and  shells  in  its  young  state,  as  here  figured,  but  afterwards  grows 

Fig.  55T. 


Heliolites  porosa,  Goldf.,  sp.  Porites  pyriformis, 
Lonsd. 

a.  Portion  of  the  same  magnified.    Middle  De- 
vonian, Torquay ;  Plymouth ;  Eifel. 


Aulopora  serpens,  Goldf. 

(The  young  basal  portion  of  a  Syringopora, 

Milne  Edw.  and  Haime.) 


upwards  and  becomes  a  cluster  of  tubes  connected  by  minute  processes: 
In  this  state  it  has  been  supposed  to  be  a  distinct  coral,  and  has  been 
called  Syringopora. 


CH.  XXVI] 


MIDDLE   DEVONIAN. 


423 


With  the  above  are  found  many  stone-lilies  or  crinoids,  some  of  them, 
such  as  Cupressocrinites,  of  forms  generically  distinct  from  those  of  the 
Carboniferous  Limestone.  The  mollusks  also  are  no  less  characteristic, 
among  which  the  genus  Stringocephalus  (fig.  558)  may  be  mentioned  as 

Fig.  558. 


Stringocephalus  Burtini,  Defr.   (Terebratula  porrecta,  Sow.)  Elfel;  also  South  Devon. 
a.  Valves  united.  Z>.  Side  view  of  same. 

c.  Interior  of  larger  valve,  showing  thick  partition,  and  part  of  a  large  process  which 
projects  from  its  upper  end  quite  across  the  shell 

exclusively  Devonian.  Many  other  Brachiopod  shells,  of  the  genus  Spir- 
ifer,  &c.,  abounded,  and  among  them  the  Atrypa  reticularis,  Linn.  sp. 
(fig.  575,  p.  434),  which  seems  to  have  been  a  cosmopolite  species  oc- 
curring in  Devonian  strata  from  America  to  Asia  Minor,  and  which,  as 
we  shall  hereafter  see  (p.  433),  lived  also  in  the  Silurian  seas.  Among 
the  peculiar  lamellibranchiate  bivalves  common  to  the  Plymouth  lime- 
stone of  Devonshire  and  the  Continent,  we  find  the  Megalodon  (fig.  559), 
together  with  many  spiral  univalves,  such  as  Murchisonia,  .Euomphalus, 
and  Macrocheilus ;  and  Pteropods  such  as  Conularia  (fig.  560).  The 

Fig.  560. 


Fig.  559. 


Megalodon  cticuttatus,  Sow.    Eifel ;  also  Bradley,  S.  Devon.         Conularia  ornata,  D'Arch.  et 
a.  The  valves  united.  Dc  Vern- 

&.  Interior  of  valve,  showing  the  large  cardinal  tooth.  (Geol.  Trans.  2d  s.  vol.  vi.  pi.  29.) 

Eefrath,  near  Cologne. 

cephalopoda,  such  as  Cyrtoceras,  Gyroceras,  and  others,  are  nearly  all  of 
genera  distinct  from  those  prevailing  in  the  Upper  Devonian  Limestone, 
or  Clymenien-kalk  of  the  Germans  already  mentioned  (p.  421).  Although 
but  few  species  of  Trilobites  occur,  the  characteristic  Brontes  flabellifer 
(fig.  561  p.  424)  is  far  more  rare,  and  all  collectors  are  familiar  with  its 
fan-like  tail.  The  head  is  seldom  found  perfect ;  a  restoration  of  it  has 
been  attempted  by  Mr.  Salter  (fig.  562). 

In  this  same  formation,  comprising  in  it  the  "  Stringocephalus  Lime- 


£24 


LOWER  DEVONIAN. 


[On.  XXVI 


Fig.  561. 


Fig.  562 


Restored  outline  of  head  of  Brontes 
Jlabellifet' 


Brontes  flalellifer>  Goldf.    Eifel ;  also  S.  Devon. 

stone,"  or  "  Eifel  Limestone"  of  Germany,  several  remains  c  Coccosteus 
and  other  ichthyolites  have  been  detected,  and  they  serve,  as  Sir  R.  Mur- 
chison  observes  (Siluria,  p. 
371),  to  identify  the  rock 
with  the  Old  Red  Sandstone 
of  Britain  and  Russia. 

Beneath   the   great  Eifel 
Limestone     (the     principal 


Fig.  563. 


Caleeola  sandalina,  Lam.    Eifel ;  also  South  Devon, 
a.  Ventral  valve.        &.  Inner  side  of  dorsal  valve. 


type  of  "  the  Devonian"  on 

the  Continent),   lie   certain 

schists    called   by   German 

writers  "  Calceola-schiefer,"  because  they  contain  in  abundance  a  fossil 

brachiopod  of  very  curious  structure,  Caleeola  sandalina  (fig.  563). 

Lower  Devonian. 

Beneath  the  Middle  Devonian  limestones  and  schists  already  enumera- 
ted, a  series  of  slaty  beds  and  quartzose  sandstones,  the  latter  constituting 
the  "  Older  Rhenish  Greywacke"  of  Roemer,  and  the  "  Spirifer  sandstone" 
of  Sandberger,  are  exhibited  between  Coblentz  and  Caub.*  A  portion  ot 
these  rocks  on  the  Rhine  and  in  some  of  the  adjacent  countries  were  re- 
garded as  '  Upper  Silurian"  by  Prof.  Sedgwick  and  Sir  R.  Murchison  in 
1839,  but  tneir  true  age  has  since  been  determined.  Their  equivalents 
are  found  in  England  in  the  sandstones  and  slates  of  the  North  Foreland 
and  Linton  in  Devon  (No.  4  and  5  of  the  section,  p.  420),  and,  ac- 
cording to  Mr.  Salter,  in  the  sandstone  of  Torbay  in  South  Devon, 
where  many  of  the  characteristic  Rhenish  fossils  are  met  with.  The 
broad-winged  Spirifers 

which    distinguish    the  Fig'564- 

"  Spirifer-sandstein"  of 
Germany  have  their  rep- 
resentatives in  the  De- 
vonian strata  of  North 

America  (see  fig.  564).  Spirifer  mucronatus,  Hall.    Devonian  of  Pennsylvania 

*  Murchison's  Siluria,  p.  368. 


CH.  XXVL] 


DEVONIAN  OF  EUSSIA. 


425 


Among  the  Trilobites  of  this  era  a  large  species  of  Homalonotus  (fig. 
565)  is  conspicuous.  The  genus  is  still  better  known  as  a  Silurian  form, 
but  the  spinose  species  appear  to  belong  exclusively  to  the  "  Lower  De- 
vonian." 

With  the  above  are  associated  many  species  of  Brachiopods,  such  as 
Orthis,  Leptama,  and  Chonetes,  and  some  Lamellibranchiata,  such  as 
Pterinea ;  also  the  very  remarkable  fossil  coral,  called  Pleurodictyum 
problematicum  (fig.  566). 


Fig.  565. 


Fig.  566. 


Pleurodictyum  problematicum,  Goldfass.  Lower 
Devonian ;  Dietz,  Nassau,  &c. 

Ola.  Attached  to  a  worm-like  body  (Serpula). 
The  specimen  is  a  cast  in  sandstone,  the  thin  ex- 
panded base  of  the  coral  being  removed,  and  ex- 
posing  the  large  polygonal  cells ;  the  walls  of  these 
cells  are  perforated,  and  the  casts  of  these  perfora- 
tions produce  the  chain-like  rows  of  dots  between 
the  cells. 


ffomalonotus  armatus,  Burmoister.    Lower 

Devonian ;  Daun,  in  the  Eifcl. 
01)8.  The  two  rows  of  spines  down  the  body 

give  an  appearance  of  more  distinct  triloba- 

tion  than  really  occurs  in  this  or  most  other 

species  of  the  genus. 

Devonian  of  Russia. — The  Devonian  strata  of  Russia  extend,  according 
to  Sir  R.  Murchison,  over  a  region  more  spacious  than  the  British  Isles ; 
and  it  is  remarkable  that,  where  they  consist  of  sandstone  like  the  "  Old 
Red"  of  Scotland  and  Central  England,  they  are  tenanted  by  fossil  fishes 
often  of  the  same  species  and  still  oftener  of  the  same  genera  as  the  Brit- 
ish, whereas  when  they  consist  of  limestone  they  contain  shells  similar  to 
those  of  Devonshire,  thus  confirming,  as  Sir  Roderick  observes,  the  con- 
temporaneous origin  previously  assigned  to  formations  exhibiting  two  very 
distinct  mineral  types  in  different  parts  of  Britain.*  The  calcareous  and 
the  arenaceous  rocks  of  Russia  above  alluded  to  alternate  in  such  a  man- 
ner as  to  leave  no  doubt  of  their  having  been  deposited  at  the  same 
period.  Among  the  fish  common  to  the  Russian  and  the  British  strata 
are  Asterolepis  Asmusii  before  mentioned ;  a  smaller  species,  A.  minor, 
Ag. ;  Holoptychius  nobilissimus  (p.  414);  Dendrodus  strigatus,  Owen ; 
Pterichthys  major,  Ag. ;  and  many  others.  But  some  of  the  most 
marked  of  the  Scottish  genera,  such  as  Cephalaspis,  Coccosteus,  Diplacan- 
thus,  Cheiracanthus,  &c.,  have  not  yet  been  found  in  Russia,  owing 
perhaps  to  the  present  imperfect  state  of  our  researches,  or  possibly  to 
geographical  causes  limiting  the  range  of  the  extinct  species.  On  the 
*  Siluria,  p.  329. 


4:26  DEVONIAN  STRATA  [On.  XX VL 

whole,  no  less  than  forty  species  of  placoid  and  ganoid  fish  have  been 
already  collected  in  Russia,  some  of  the  placoids  being  of  enormous  size, 
as  before  stated,  p.  419. 

Devonian  Strata  in  the  United  States. 

In  no  country  hitherto  explored  is  there  so  complete  a  series  of  strata 
intervening  between  the  Carboniferous  and  Silurian  as  in  the  United 
States.  This  intermediate  or  Devonian  group  was  first  studied  in  all  its 
details,  and  with  due  attention  to  its  fossil  remains,  by  the  Government 
Surveyors  of  New  York.  In  its  geographical  extent,  that  State,  taken 
singly,  is  about  equal  in  size  to  Great  Britain  ;  and  the  geologist  has  the 
advantage  of  finding  the  Devonian  rocks  there  in  a  nearly  horizontal  and 
undisturbed  condition,  so  that  the  relative  position  of  each  formation  can 
be  ascertained  with  certainty. 

Subdivisions  of  the  New  York  Devonian  Strata,  in  the  Reports  of  the 
Government  Surveyors. 

Names  of  Groups.  Thickness  in  Feet 

1.  Catskill  group  or  Old  Red  Sandstone       ....  2000 

2.  Chemung  group 1500 

3.  Portage  )  1000 

4.  Genesee  f 

5.  Tully -    -                '-    "  -         -  15 

6.  Hamilton ...  1000 

7.  Marcellus 50 

8.  Corniferous  )  ^ 

9.  Onondaga     J 

10.  Schoharie  ) 

11.  Cauda-Galli  grit  \ 

12.  Oriskany  sandstone       '  -        -        -        "-••"""  -'       -          6  to  30 

These  subdivisions  are  of  very  unequal  value,  whether  we  regard  the 
thickness  of  the  beds  or  the  distinctness  of  their  fossils ;  but  they  have 
each  some  mineral  or  organic  character  to  distinguish  them  from  the 
rest.  Moreover,  it  has  been  found,  on  comparing  the  geology  of  other 
North  American  States  with  the  New  York  standard,  that  some  of  the 
above-mentioned  groups,  such  as  Nos.  2  and  3,  which  are  respectively 
1500  and  1000  feet  thick  in  New  York,  are  very  local  and  thin  out  when 
followed  into  adjoining  States ;  whereas  others,  such  as  Nos.  8  and  9,  the 
total  thickness  of  which  is  scarcely  50  feet  in  New  York,  can  be  traced 
over  an  area  nearly  as  large  as  Europe. 

Respecting  the  upper  limit  of  the  above  system,  there  has  been  very 
little  difference  of  opinion,  since  the  Red  Sandstone  No.  1  contains 
Holoptychius  nobilissimus  and  other  fish  characteristic  generically  or 
specifically  of  the  European  Old  Red.  More  doubt  has  been  entertained 
in  regard  to  the  classification  of  Nos.  10,  11,  and  12.  M.  de  Yerneuil 
proposed  in  1847,  after  visiting  the  United  States,  to  include  the  Oriskany 
sandstone  in  the  Devonian  ;  and  Mr.  D.  Sharpe,  after  examining  the  fossils 
which  I  had  collected  in  America  in  1842,  arrived  independently  at  the 


CH.  XXVL]  IN  THE  UNITED  STATES.  4:27 

same  conclusion.*  The  resemblance  of  the  Spirifers  of  this  Oriskany 
sandstone  to  those  of  the  Lower  Devonian  of  the  Eifel  was  the  chief  mo- 
tive assigned  by  M.  de  Verneuil  for  his  view  ;  and  the  overlying  Schoharie 
grit,  No.  10,  was  classed  as  Devonian  because  it  contained  a  species  of 
Asterolepis.  On  the  other  hand,  Prof.  Hall  adduces  many  fossils  from 
Nos.  10  and  12  which  resemble  more  nearly  the  Ludlow  group  of  Mur- 
chison  than  any  other  European  type  ;  and  he  thinks,  therefore,  that  those 
groups  may  be  "  Upper  Silurian."  Although  the  Oriskany  sandstone  is 
no  more  than  30  feet  thick  in  New  York,  it  is  sometimes  300  feet  thick  in 
Pennsylvania  and  Virginia,  where,  together  with  other  primary  or  paleo- 
zoic strata,  it  has  been  well  studied  by  Professors  W.  B.  and  H.  D.  Rogers. 
The  upper  divisions  (from  the  Catskill  to  the  Genesee  groups,  inclu- 
sive, Nos.  1  to  4)  consist  of  arenaceous  and  shaly  beds,  and  may  have 
been  of  littoral  origin.  They  vary  greatly  in  thickness,  and  few  of  them 
can  be  traced  into  the  "  far  west ;"  whereas  the  calcareous  groups,  Nos. 
8  and  9,  although  in  New  York  they  have  seldom  a  united  thickness  of 
more  than  50  feet,  are  observed  to  constitute  an  almost  continuous  coral- 
reef  over  an  area  of  not  less  than  500,000  square  miles,  from  the  State  of 
New  York  to  the  Mississippi,  and  between  Lakes  Huron  and  Michigan,  in 
the  north,  and  the  Ohio  River  and  Tennessee  in  the  south.  In  the 
Western  States  they  are  represented  by  the  upper  part  of  what  is  termed 
"  the  Cliff  Limestone."  There  is  a  grand  display  of  this  calcareous  for- 
mation at  the  falls  or  rapids  of  the  Ohio  River  at  Louisville  in  Kentucky, 
where  it  much  resembles  a  modern  coral-reef.  A  wide  extent  of  surface 
is  exposed  in  a  series  of  horizontal  ledges,  at  all  seasons  when  the  water 
is  not  high ;  and,  the  softer  parts  of  the  stone  having  decomposed  and 
wasted  away,  the  harder  calcareous  corals  stand  out  in  relief,  their  erect 
stems  sending  out  branches  precisely  as  when  they  were  living.  Among 
other  species  I  observed  large  masses,  not  less  than  5  feet  in  diameter,  of 
Favosites  gothlandica,  with  its  beautiful  honeycomb  structure  well  dis- 
played, and,  by  the  side  of  it,  the  Favistella,  combining  a  similar  honey- 
combed form  with  the  star  of  the  Astrcea.  There  was  also  the  cup- 
shaped  Cyathophyllum,  and  the  delicate  network  of  the  Fenestella,  and 
that  elegant  and  well-known  European  species  of  fossil,  called  "  the  chain 
coral,"  Catenipora  escharoides  (see  fig.  579,  p.  435),  with  a  profusion  of 
others.  These  coralline  forms  were  mingled  with  the  joints,  stems,  and 
occasionally  the  heads  of  lily  encrinites.  Although  hundreds  of  fine 
specimens  have  been  detached  from  these  rocks  to  enrich  the  museums 
of  Europe  and  America,  another  crop  is  constantly  working  its  way  out, 
under  the  action  of  the  stream,  and  of  the  sun  and  rain  in  the  warm  sea- 
son when  the  channel  is  laid  dry.  The  waters  of  the  Ohio,  when  I  visited 
the  spot  in  April,  1846,  were  more  than  40  feet  below  their  highest  level, 
and  20  feet  above  their  lowest,  so  that  large  spaces  of  bare  rock  were  ex- 
posed to  view.f 

*  De  Verneuil,  Bulletin,  4,  678,  1847.   D.  Sharpe,  Quart.  Journ.  Geol.  Soc.  vol 
iv.  pp.  145,  1847. 

f  Ly ell's  Second  Visit  to  the  Ucited  States,  vol  li.  p.  277. 


428  DEVONIAN  STKATA.  [On.  XXVI. 

No  less  than  46  species  of  British  Devonian  corals  are  described  in  the 
Monograph  published  in  1853  by  Messrs.  M.  Edwards  and  Jules  Haime 
(Paleontographical  Society),  and  only  six  of  these  occur  in  America ;  a 
fact,  observes  Prof.  E.  Forbes,  which,  when  we  call  to  mind  the  wide  lati- 
tudinal range  of  the  Anthozoa,  has  an  important  bearing  on  the  deter- 
mination of  the  geography  of  the  northern  hemisphere  during  the  Devo- 
nian epoch.  We  must  also  remember  that  the  corals  of  these  ancient 
reefs,  whether.  American  or  European,  however  recent  maybe  their  aspect, 
all  belong  to  the  Zoantharia  rugosa,  a  suborder  which,  as  before  stated 
(p.  403,  et  seq.),  has  no  living  representative.  Hence  great  caution  must 
be  used  in  admitting  all  inductions  drawn  from  the  presence  and  forms  of 
these  zoophytes,  respecting  the  prevalence  of  a  warm  or  tropical  climate 
in  high  latitudes  at  the  time  when  they  flourished, — for  such  inductions, 
says  Prof.  E.  Forbes,  have  been  founded  "  on  the  mistaking  of  analogies 
for  affinities."* 

This  calcareous  division  also  contains  Goniatites,  Spirifers,  Pentre- 
mites,  and  many  other  genera  of  Mollusca  and  Crinoidea,  corresponding 
to  those  which  abound  in  the  Devonian  of  Europe,  and  some  few  of  the 
forms  are  the  same.  But  the  difficulty  of  deciding  on  the  exact  parallelism 
of  the  New  York  subdivisions,  as  above  enumerated,  with  the  members 
of  the  European  Devonian,  is  very  great,  so  few  are  the  species  in  com- 
mon. This  difficulty  will  best  be  appreciated  by  consulting  the  critical 
essay  published  by  Mr.  Hall  in  1851,  on  the  writings  of  European  authors 
on  this  interesting  question. f  Indeed  we  are  scarcely  as  yet  able  to  de- 
cide on  the  parallelism  of  the  principal  groups  even  of  the  north  and 
south  of  Scotland,  or  on  the  agreement  of  these  again  with  the  Devonian 
and  Rhenish  subdivisions. 

*  Geol.  Quart.  Journ.  vol.  x.  pi.  Ix.  1854. 

f  Report  of  Foster  and  Whitney  on  Geol.  of  Lake  Superior,  p.  802,  Washing- 
ton, 1851. 


CH.  XXVIL]  SILURIAN  STRATA.  429 


CHAPTER  XXVIL 

SILURIAN    AND    CAMBRIAN    GROUPS. 

Silurian  strata  formerly  called  Transition — Term  Grauwacke — Subdivisions  of 
Upper,  Middle,  and  Lower  Silurians — Ludlow  formation  and  fossils — Ludlow 
bone-bed,  and  oldest  known  remains  of  fossil  fish — Wenlock  formation,  corals, 
cystideans,  trilobites — Middle  Silurian  or  Caradoc  sandstone — Its  tmconforma- 
bility — Pentameri  and  Tentaculites — Lower  Silurian  rocks — Llandeilo  flags — 
Cystideae — Trilobites — Graptolites — Vast  thickness  of  Lower  Silurian  strata  in 
Wales — Foreign  Silurian  equivalents  in  Europe — Ungulite  grit  of  Eussia — 
Silurian  strata  of  the  United  States — Amount  of  specific  agreement  of  fossils 
with  those  of  Europe — Canadian  equivalents — Deep-sea  origin  of  Silurian 
strata — Fossiliferous  rocks  below  the  Llandeilo  beds — Cambrian  group — Lin- 
gula  flags  of  North  Wales — Lower  Cambrian — Oldest  known  fossil  remains — 
"  Primordial  group"  of  Bohemia — Characteristic  trilobites — Metamorphosis  of 
trilobites — Alum  schists  of  Sweden  and  Norway — Potsdam  sandstone  of  United 
States  and  Canada — Footprints  near  Montreal — Trilobites  on  the  Upper  Mis- 
sissippi— Supposed  period  of  invertebrate  animals — Upper  Silurian  bone-bed 
— Absence  of  fish  in  Lower  Silurian — Progressive  discovery  of  vertebrata  in 
older  rocks — Inference  to  be  drawn  from  the  greater  success  of  British  Pa- 
leontologists— Doctrine  of  the  non-existence  of  vertebrata  in  the  older  fossilif- 
erous  periods  premature. 

WE  come  next  in  the  descending  order  to  the  most  ancient  of  the 
primary  fossiliferous  rocks,  that  series  which  comprises  the  greater  part  of 
the  strata  formerly  called  *'  transition"  by  Werner,  for  reasons  explained 
in  chap,  viii.,  pp.  91  and  93.  Geologists  were  also  in  the  habit  of  ap- 
plying to  these  older  strata  the  general  name  of  "  grauwacke,"  by  which 
the  German  miners  designate  a  particular  variety  of  sandstone,  usually  an 
aggregate  of  small  fragments  of  quartz,  flinty  slate  (or  Lydian  stone),  and 
clay-slate  cemented  together  by  argillaceous  matter.  Far  too  much  im- 
portance has  been  attached  to  this  kind  of  rock,  as  if  it  belonged  to  a 
certain  epoch  in  the  earth's  history,  whereas  a  similar  sandstone  or 
grit  is  found  in  the  Old  Red,  and  in  the  Millstone  Grit  of  the  Coal, 
and  sometimes  in  certain  Cretaceous  and  even  Eocene  formations  in  the 
Alps. 

The  name  of  Silurian  was  first  proposed  by  Sir  Roderick  Murchison 
for  a  series  of  fossiliferous  strata  lying  below  the  Old  Red  Sandstone,  and 
occupying  that  part  of  Wales  and  some  contiguous  counties  of  England 
which  once  constituted  the  kingdom  of  the  Silures,  a  tribe  of  ancient 
Britons.  The  following  table  will  explain  the  various  formations  into 
which  this  group  of  ancient  strata  may  be  subdivided. 


430 


SUBDIVISIONS  OF  SILURIAN  ROCKS.         [Ca  XXVIL 


UPPER  SILURIAN  ROCKS. 


Prevailing  Lithological        ™ck- 

/»Viaro/»tora                     iioeo  in                v^rgdiiio  rtuiuiiio. 

Feet. 

r 

r  a.  Tilestones.  —  "|                "] 

Finely      lamina-  1 

Marine  mollusca  of 

ted  reddish  and  I  800  ? 

almost  every  or- 

T 

green  micaceous 

der,  the  Brachio- 

Upper 
Ludlow. 

sandstones. 

poda  most  abun- 

dant. Serpulites, 

b.  Micaceous  gray  " 

Crustaceans      of 

1.  Ludlow 

sandstone      and 

the  Trilobite  fa- 

formation. " 

mudstone. 

mily.         Placoid 

fish    (oldest    re- 

Aymestry 
limestone. 

Argillaceous  lime- 
stone. 

-  2000 

mains  of  fish  yet 
known).         Sea- 

weeds ;     and    in 

Lower 
Ludlow. 

!  Shale,  with  concre- 
tions   of    lime- 

the     uppermost 
strata  land  plants. 

stone. 

!    Wenlock 
limestone. 
1 

1  Concretionary  and  " 
thick-bedded 
limestone. 

1  Marine  Mollusca  of 
various  orders  as 
^.UVYC    ,      before.  Crinoidea 

. 

Wenlock     ' 
shale.       " 

Argillaceous  shale, 
frequently  flag- 
stone. 

*    2000     [      and  corals  plenti- 
ful.      Trilobites, 
Graptolites. 

MIDDLE  SILURIAN  ROCKS. 


Caradoc    j 
formation.  ( 


Llandeilo   j 
formation.     ( 


Caradoc 
sandstones. 


Shale,  shelly  lime-  "| 


Cr°idea' 


,  -  11 

stone,  sandstone,  I     onnn  Mollusca,  chiefly 

and     conglome'-        «>00    j  gj-Jj^ 

[  merus  abundant.) 


LOWER  SILURIAN  ROCKS. 


Llandeilo     I 


C  Dark  colored  cal-  ~) 
careous      flags  ;   ^ 


slates  and  sand- 
stones. 


20,000  J 


f  Mollusca,  Trilo- 
bites, Cystideae, 
Crinoids,  Corals, 

[_     Graptolites. 


'UPPER    SILURIAN    ROCKS. 


Ludlow  formation.  —  This  member  of  the  Upper  Silurian  group,  as 
will  be  seen  by  the  above  table,  is  of  great  thickness,  and  subdivided 
into  three  parts,  —  the  Uppe  :  and  the  Lower  Ludlow,  and  the  intervening 
Aymestry  limestone.  Each  of  these  may  be  distinguished  near  the  town 
of  Ludlow,  and  at  other  places  in  Shropshire  and  Herefordshire  by  pe- 
culiar organic  remains. 

1.  Upper  Ludlow,  a.  Tilestones.  —  This  uppermost  subdivision,  called 
the  Tilestones,  was  originally  classed  by  Sir  R.  Murchison  with  the  Old 
Red  Sandstone,  because  they  decompose  into  a  red  soil  throughout  the 
Siluiian  region.  They  were  regarded  as  a  transition  group  forming  a 
passage  from  Silurian  to  Old  Red  ;  but  it  is  now  ascertained  that  the 
fossils  agree  in  great  part  specifically,  and  in  general  character  entirely, 
with  those  of  the  underlying  Silurian  strata.  Among  these  are  Ortho- 


CH.  XXVIL]  UPPER  SILURIAN   BONE-BED.  431 

ceras  bullatum,  Trochus  ?  helicites,  Bellerophon  trilobatus,  Ckonetes  lata, 
<fec.,  with  numerous  defences  of  fishes.  These  beds  are  well  seen  at  King- 
ton  in  Herefordshire,  and  at  Downton  Castle  near  Ludlow,  where  they 
are  quarried  for  building. 

b.  Gray  Sandstone,  &c. — The  next  subdivision  of  the  Upper  Ludlow 
consists  of  gray  calcareous  sandstone,  or  very  commonly  a  micaceous 
stone,  decomposing  into  soft  mud,  and  contains,  besides  the  shells  just 
quoted,  the  Lingula  cornea,  which  is  common  to  it  and  the  Tilestone  beds. 
The  Orthis  orbicularis,  a  round  variety  of  0.  elegantula,  is  characteristic 
of  the  Upper  Ludlow  ;  and  the  lowest  or  mudstone  beds  are  loaded  for  a 
thickness  of  30  feet  with  Athyris  navicula  (fig.  568).  As  usual  in  strata 
of  the  Primary  periods,  the  brachiopodous  mollusca  predominate  over  the 

Fig.  567.  Fig.  568. 


Orthts  elegantula,  Dalm.    Var.  orbicularis,       Athyris  (Terebratulcf)  navicttla,  J.  Sow. 
J.  Sow.    Delbury.  Aymestry  limestone ;  also  in 

Upper  Ludlow.  Upper  and  Lower  Ludlow. 

lamellibranchiate ;  but  the  latter  are  by  no  means  unrepresented.  Among 
other  genera,  for  example,  we  observe  Avicula  (or  Pterinea),  Cardiola, 
Nucula,  Sanguinolites,  and  Modiola. 

Some  of  the  Upper  Ludlow  sandstones  are  ripple-marked,  thus  afford- 
ing evidence  of  gradual  deposition ;  and  the  same  may  be  said  of  the  ac- 
companying fine  argillaceous  shales  which  are  of  great  thickness,  and  have 
been  provincially  named  "  mudstones."  In  some  of  these  shales  stems  of 
crinoidea  are  found  in  an  erect  position,  having  evidently  become  fossil  on 
the  spots  where  they  grew  at  the  bottom  of  the  sea.  The  facility  with 
which  these  rocks,  when  exposed  to  the  weather,  are  resolved  into  mud, 
proves  that,  notwithstanding  their  antiquity,  they  are  nearly  in  the  state 
in  which  they  were  first  thrown  down. 

The  bone-bed  of  the  Upper  Ludlow  deserves  especial  notice  as  affording 
the  oldest  well-authenticated  example  of  the  fossil  remains  of  fish.  It 
usually  consists  of  a  single  thin  layer  of  brown  bony  fragments  near  the 
junction  of  the  Old  Red  Sandstone  and  the  Ludlow  rocks,  and  was  first 
observed  by  Sir  R.  Murchison,  near  the  town  of  Ludlow,  where  it  is  three 
or  four  inches  thick.  It  has  since  been  traced  to  a  distance  of  45  miles 
from  that  point  into  Gloucestershire  and  other  counties,  and  is  commonly 
not  more  than  an  inch  thick.  At  May  Hill  two  bone-beds  were  observed, 
with  14  feet  of  intervening  strata  full  of  Upper  Ludlow  fossils.*  At  that 
point  immediately  above  the  upper  fish-bed  numerous  globular  bodies 
were  found,  which  were  determined  by  Dr.  Hooker  to  be  the  spores  of  a 
cryptogamic  land-plant,  probably  Lycopodiaceous.  These  beds  occur  just 

*  Murchison's  Siluria,  pp.  137-237. 


4:32  FOSSILS  OF   UPPER  LUDLOW.  [On.  XXVII. 

beneath  the  lowest  strata  of  the  "  Old  Red."  Some  of  the  fish  are  of  the 
shark  family,  and  their  defences  are  referred  to  the  genus  Onchus  (fig. 
569).  There  are  also  numerous  minute  shagreen  scales  (fig.  570),  which 

Fig.  569.  Fig.  570. 


.  Onchus  tenuistriatus,  Agass.  Shagreen  scales  of  a  placoid  fish 

Bone-bed.    Upper  Silurian ;  Ludlow.  (Thelodus). 

Bone-bed.    Upper  Ludlow. 

may  possibly  belong  to  the  same  placoid  fish.     The  jaw  and  teeth  of 
another  predaceous  genus  (fig.  571)  have  also  Fig.  571. 

been  detected.  As  usual  in  bone-beds,  the 
teeth  and  bones  are,  for  the  most  part,  frag- 
mentary and  rolled.  Many  statements  have  piectrodusmiraUUs, Agass. 
been  published  of  fish  remains  obtained  from  Bone-bed.  Upper  Ludlow. 
older  members  of  the  silurian  series ;  but  Mr.  Salter  has  shown  all 
these  to  be  spurious.*  Professor  Phillips  has,  however,  discovered  fish- 
bones at  the  bottom  of  the  "  Upper  Ludlow,"  at  its  junction  with  the 
Aymestry  Rock  ;f  and  lower  than  this  no  one  seems  as  yet  to  have  suc- 
ceeded in  tracing  them  downwards,  whether  in  Europe  or  North  America, 
for  M.  Barrande's  most  ancient  ichthyolites  (bony  fragments,  8  inches 
long)  occur  in  the  Upper  Silurian  of  Bohemia ;  and  those  of  the  American 
Geologists  are  from  the  Oriskany  Sandstone,  a  formation  which  is  still 
considered  as  debatable  ground  between  the  Devonian  and  Silurian  sys- 
tems (see  p.  426,  above). 

In  England  it  is  true,  as  in  the  United  States  and  Canada,  globular, 
cylindrical,  or  flattened  masses  have  been  detected,  composed  principally 
of  phosphate  of  lime,  in  the  Lowest  Silurian  rocks,  and  they  have  been 
suspected  to  be  coprolitic.  Messrs.  Logan  and  Hunt  have  recently  shown 
that  shells  of  the  genera  Lingula  and  Orbicula,  which  occur  abundantly 
in  the  same  formations,  are  also  made  up  of  phosphate  and  carbonate  of 
lime,  mixed  in  the  like  proportions  ;  and  it  has  been  suggested  that  the 
decomposition  of  such  shells  might  give  rise  to  the  nodules  alluded  to, 
which  may  owe  their  form  to  concretionary  action.J  Even  if  the  zoologist 
should  think  it  more  likely  that  the  phosphatic  matter  was  rejected  in 
fcecal  lumps,  by  creatures  feeding  on  Lingulse  a,nd  Orbiculse,  we  cannot 
decide  that  such  feeders  were  of  the  vertebrate  class,  rather  than.  Cepha- 
lopods,  Crustaceans,  or  some  other  of  the  Invertebrata.  In  regard  to  the 
doctrine  of  the  supposed  non-existence  of  fish  in  the  Silurian  seas  before 
the  time  of  the  Ludlow  bone-bed,  I  shall  consider  that  question  fully  in 
the  concluding  pages  of  this  chapter,  p.  453,  et  seq. 

*  Geol.  Quart.  Journ.  vol.  vii.  p.  263. 

f  Memoirs  Geol.  Surv.  vol.  ii. 

\.  Logan  and  Hunt ;  Silliman's  Journ.  No.  50,  2d  series,  March,  1854. 


OH.  XXVII.  j 


AYMESTEY  LIMESTONE. 


433 


2.  Aymestry  limestone. — The  next  group  is  a  subcrystalline  and 
argillaceous  limestone,  which  is  in  some  places  50  feet  thick,  and  dis- 
tinguished around  Aymestry  by  the  abundance  of  Pentamerus  Knightly 
Sow.  (fig.  572),  also  found  in  the  Lower  Ludlow.  This  genus  of  brachi- 


Fig.  572. 


Pentamerus  Knightii,  Sow.    Aymestry.    Half  nat  size. 
a.  View  of  both  valves  united. 
&.  Longitudinal  section  through  both  valves,  showing  the  central  plates  :'  septa. 

opoda  was  first  found  in  Silurian  strata,  and  is  exclusively  a  paleozoic 
form.  The  name  was  derived  from  rtsvrs,  pente,  five,  and  ju.££o£,  meros, 
a  part,  because  both  valves  are  divided  by  a  central  septum,  making  four 
chambers,  and  in  one  valve  the  septum  itself  contains  a  small  chamber, 
making  five.  The  size  of  these  septa  is  enormous  compared  with  those 
of  any  other  brachiopod  shell ;  and  they  must  nearly  have  divided  the 
animal  into  two  equal  halves ;  but  they  are,  nevertheless,  of  the  same 
nature  as  the  septa  or  plates  which  are  found  in  the  interior  of  Spirifer, 
Tcrebratula,  and  many  other  shells  of  this  order.  Messrs.  Murchison 
and  De  Verneuil  discovered  this  species  dispersed  in 
myriads  through  a  white  limestone  of  Upper  Silurian 
age,  on  the  banks  of  the  Is,  on  the  eastern  flank  of 
the  Urals  in  Russia,  and  a  similar  species  is  frequent 
in  Sweden. 

Three  other  abundant  shells  in  the  Aymestry  lime- 
stone are,  1st,  Lingula  Lewisii  (fig.  573)  ;  2d, 
Rhynchonella  Wilsoni,  Sow.  (fig.  574),  which  is  also 
common  to  the  Lower  Ludlow  and  Wenlock  lime- 
stone ;  3d,  Atrypa  reticularis,  Lin.  (fig.  575),  which 
has  a  very  wide  range,  being  found  in  every  part  ol 
the  Silurian  system,  even  in  the  upper  portion  of  the 


Fig.  5 


Lingula  Lewisii, 

J.  Sow. 
Abberley  Hills, 


Llandeilo  flags. 


Fig.  574. 


Rhynchonella  (Terebratuld)  Wilsoni,  Sovr.    Aymeetry. 
28 


434 


FOSSILS  OF  LOWER  LUDLOW.  [Cn.  XXVII 

Fig.  575. 


Fig.  5T6. 


Atrypa  reticularis,  Linn.    (Terebratula  affinis,  Min.  Con.)    Aymestry. 
a.  Upper  valve.  &.  Lower  valve. 

c.  Anterior  margin  of  the  valves. 

The  Aymestry  Limestone  contains  so  many  shells,  corals,  and  trilobites 
agreeing  specifically  with  those  of  the  subjacent  Wenlock  limestone,  that 
it  is  scarcely  distinguishable  from  it  by  its  fossils  alone.  Nevertheless, 
many  of  the  organic  remains  are  common  to 
the  Aymestry  limestone  and  the  Upper  Lud- 
low, and  several  of  these  are  not  found  in  the 
Wenlock* 

3.  Lower  Ludlow  shale. — This  mass  is  a 
dark  gray  argillaceous  deposit,  containing, 
among  other  fossils,  many  large  chambered 
shells  of  genera  scarcely  known  in  newer 
rocks,  as  the  Phragmoceras  of  Broderip,  and 
the  Lituites  of  Breyn  (see  figs.  576,  577). 
The  latter  is  partly  straight  and  partly  con- 
voluted, nearly  as  in  Spirula, 
Phragmoceras  ventricosum,  j.  Sow.  The  Orthoceras  Ludense  (fig.  578),  as 

(Orthoceras  ventricosum,  St«in.)  ,,  ,,  ,     ,         11,  ,•         j 

Aymestry ;  £  nat.  size.  well  as  the  cephalopod  last  mentioned,  is 

peculiar  to  this  member  of  the  series. 

Fig.  577.  Fig.  578. 


Lituites  giganteus,  J.  Sow. 
Near  Ludlow ;  also  in  the  Aymestry 
and  Wenlock  limestones;  \  nat  size. 


Fragment  of  Orthoceras  Ludense,  J.  Sow. 
Lcintwardine,  Shropshire. 


A  species  of  Graptolite,  G.  Ludensis,  Murch.  (fig.  588,  p.  437),  a  form 
of  zoophyte  which  has  not  yet  been  met  with  in  strata  above  the  Silurian, 
Dccurs  plentifully  in  the  Lower  Ludlow. 

*  Murchison's  Siluria,  p.  133. 


Cn.  XXVIL] 


WEXLOCK   FORMATION. 


435 


Fig.  5T9. 


Wenlock  formation. — We  next  come  to  the  Wenlock  formation,  which 
has  been  divided  (see  Table,  p.  430)  into  the  Wenlock  limestone  and  the 
Wenlock  shale. 

1.  The  Wenlock  limestone,  formerly  well  known  to  collectors  by  the 
name  of  the  Dudley  limestone,  forms  a  continuous  ridge  in  Shropshire, 
ranging  for  about  20  miles  from  S.  W.  to  N.E.,  about  a  mile  distant  from 
the  nearly  parallel  escarpment  of  the  Aymestry  limestone.  This  ridgy 
prominence  is  due  to  the  solidity  of  the  rock,  and  to  the  softness  of  the 
shales  above  and  below  it.  Near  Wenlock  it  consists  of  thick  masses  of 
gray  subcrystalline  limestone,  replete  with  corals  and  encrinites.  It  is 
essentially  of  a  concretionary  nature,  and  the  concretions,  termed  "  ball- 
stones"  in  Shropshire,  are  often  enormous,  even 
80  feet  in  diameter.  They  are  of  pure  carbo- 
nate of  lime,  the  surrounding  rock  being  more 
or  less  argillaceous.*  Sometimes  in  the  Mal- 
vern  Hills  this  limestone,  according  to  Professor 
Phillips,  is  oolitic. 

Among  the  corals  in  which  this  formation  is 
so  rich,  the  "  chain-coral,"  Halysites  catenula- 
tus,  or  Catenipora  escharoides  (fig.  579),  may 
be  pointed  out  as  one  very  easily  recognized, 
and  widely  spread  in  Europe,  ranging  through 
all  parts  of  the  Silurian  group,  from  the 
Aymestry  limestone  to  near  the  bottom  of  the 
series.  Another  coral,  the  Favorites  Goth- 
landica  (fte.  580),  is  also  met  with  in  profusion  Syo.  Cateni 

v  °  ''  .     .  Gold.  Upper  and  Lower  Silurian. 

in  large  hemispherical  masses,  which  break  up 

into  prismatic  fragments,  like  that  here  figured  (fig.  580).  Another 
common  form  in  the  Wenlock  limestone  is  the  Omphyma  (fig.  581), 
which,  like  many  of  its  companions,  reminds  us  of  some  modern  cup- 
corals,  but  all  the  Silurian  genera  belong  to  the  paleozoic  type  before  men- 


Fig.  5SO. 


Fig.  581. 


Fdtositfs  Gothlandica.  Lam.    Dudley. 

a.  Portion  of  a  large  mass;  less  than  the 

natural  size. 

b.  Magnified  portion  to  show  the  pores 

and  the  partitions  in  the  tubes. 


Omphyma  turbinatum,  Linn.  sp. 

(Cyathophyllum,  Gold£) 
Wenlock  Limestone,  Shropshire. 


*  Murcbison's  Siluria,  p.  115. 


436 


FOSSILS   OF  THE  WENLOCK  LIMESTONE.     [Cn.  XXVII 


tioned  (p.  403),  exhibiting  the  quadripartite  arrangement  of  the  lamellae 
within  the  cup. 

Among  the  numerous  Crinoids,  several  peculiar  species  of  Cyathocrinus 
(for  genus,  see  figs.  p.  405)  contribute  their  calcareous  stems,  arms,  and 
cups  towards  the  composition  of  the  Wenlock  limestone.  Of  Cystideans 
there  are  a  few  very  remarkable  forms,  some  of  them  peculiar  to  the 
Upper  Silurian  formation,  as  for  example  the  Pseudocrinites,  which  was 
furnished  with  pinnated  fixed  arms,*  as  represented  in  the  annexed  fig- 
ure (fig.  582). 

The  Brachiopoda  are  for  the  most  part  of  the  same  species  as  those  of 
the  Aymestry  limestone ;  as,  for  example,  Atrypa  reticularis  (fig.  575, 
p.  434),  and  Strophomena  depressa,  Sow.  sp.  (fig.  583)  ;  but  these  species 
range  also  through  the  Ludlow  rocks,  Wenlock  shale,  and  Caradoc 
Sandstone. 

Fig.  582. 


Fig.  583. 


Strophomena  (Leptcena)  depretsa,  Sow. 
Wenlock  and  Ludlow  Eocks. 

Pseudocrinites  Mfasciatus,  Pearce. 
Wenlock  limestone,  Dudley. 

The  Crustaceans  are  represented  almost  exclusively  by  Trilobites,  which 
are  very  conspicuous.  The  Calymene  Blumenbachii,  called  the  "  Dudley 
Trilobite,"  was  known  to  collectors  long  before  its  true  place  in  the  animal 
kingdom  was  ascertained.  It  is  often  found  coiled  up  like  the  common 
Oniscus  or  wood-louse,  .and  this  is  so  common  a  circumstance  among  the 
trilobites  as  to  lead  us  to  conclude  that  they  must  have  habitually  resorted 
to  this  mode  of  protecting  themselves  when  alarmed.  Sphcerexochus 

Fig.  595. 


Fig.  584 


Calymene  Blwnenbaehii, 

Brong. 

Wenlock,  Ludlow,  and 
Aymestry  limestones. 


Fig.  586. 


Sphcerexochus  minis,  Bey- 
rich.    Coiled  up. 
Dudley;  also  in  Ohio, 
N,  America. 


Phacops  caudatu*,  Brong. 
Wenlock,  Aymestry,  and  Ludlow  Eocks. 

*  E.  Forbes,  Mem.  Geol.  Survey,  vol.  ii.  p.  496. 


CH.  XXVIL] 


MIDDLE  SILURIAN  ROCKS. 


437 


mirus  (fig.  586)  is  almost  a  globe  when  rolled  up,  the  forehead  of  this 
species  being  extremely  inflated.  The  Homalonotus,  a  form  of  Trilobite 
in  which  the  tripartite  division  of  the  dorsal  crust  is  j-ig>  587. 

almost  lost  (see  fig.  587),  is  very  characteristic  of 
this  division  of  the  Silurian  series. 

2.  The  Wenlock  Shale.  —  This,  observes  Sir  R. 
Murchison,*  is  infinitely  the  largest  and  most  per- 
sistent member  of  the  Wenlock  formation,  for  the 
limestone  often  thins  out  and  disappears.  The  shale, 
like  the  Lower  Ludlow,  often  contains  elliptical  con- 
cretions of  impure  earthy  limestone.  In  the  Malvern 
district  it  is  a  mass  of  finely  levigated  argillaceous 
matter,  attaining,  according  to  Prof.  Phillips,  a  thick- 
ness of  640  feet,  but  it  is  sometimes  more  than  1000 
feet  thick  in  Wales.  The  prevailing  fossils,  besides 
corals  and  trilobites,  and  some  crinoids,  are  several 
small  species  of  Or  this,  with  other  brachiopods  and 
certain  thin-shelled  species  of  Orthoceratites.  One 
species  of  G-raptolite,  a  group  of  zoophytes  before 
alluded  to  as  being  confined  to  Silurian 
rocks,  is  very  abundant  in  this  shale,  and 

occurs  more  sparingly  in  "  the  Ludlow."       araptoiithm  Ludenti*,  Murchison. 
Of  these  fossils,  which  are  more  charac-  Ludlow  and  Wenlock  Shales. 

teristic  of  the  Lower  Silurian,  I  shall  again  speak  in  the  sequel  (p.  442). 


-v»a^ssSSS$!^ 


MIDDLE    SILURIAN    ROCKS. 

Caradoc  Sandstone.  —  This  sandstone,  so  named  from  a  mountain  called 
Caer  Caradoc,  in  Shropshire,  was  originally  considered  by  Sir  Roderick 
Murchison  as  the  sandy  and  upper  portion  of  the  Lower  Silurian  strata. 
Subsequent  investigations  have  led  to  the  conclusion  that  the  original  c^ 
typical  Caradoc  is  divisible  into  two  formations,  —  the  lower,  an  arenaceous 
form  of  Llandeilo  flags,  and  containing  identical  species  of  fossils  ;  the 
other  or  superior  sandstone,  a  series  of  strata  resting  unconformably  on  the 
Llandeilo  beds,  and  chiefly,  characterized  by  Upper  Silurian  fossils,  yet 
having  some  intermixture  of  species  common  to  the  "  Lower  Silurian." 
Hence  the  Caradoc,  as  distinct  from  the  Llandeilo,  must  either  be  classed 
as  the  base  of  the  Wenlock  Shale,  an  opinion  to  which  some  authorities 
incline,—  or  it  may  be  regarded  as  a  Middle  Silurian  group,  an  alternative 
which  I  have  embraced  provisionally  in  common  with  many  officers  ot 
our  Government  Survey.  The  larger  part,  therefore,  of  what  was  once 
termed  "  the  Caradoc"  has  merged  into  the  Llandeilo,  and  is  the  equiva- 
lent of  the  upper  and  middle  portions  of  that  division. 

The  first  step  towards  placing  in  a  clearer  light  the  relations  of  "  the 
Caradoc"  to  the  strata  above  and  below  it,  was  made  in  1848  by  Professor 


*  Siluria,  p.  111. 


438  CARADOC  SANDSTONE.  [Cn.  XXVII. 

Ramsay  and  Mr.  Aveline,  who  observed  that  in  the  Longmynd  Hills  the 
Caradoc  sandstone  rested  unconformably  on  the  Lower  Silurian,  and  that 
the  latter  or  "  Llandeilo  flags,"  together  with  some  still  older  rocks,  must 
have  constituted  an  island  in  the  Caradoc  sea.  Professor  E.  Forbes  at  the 
same  time  observed  that  the  island  was  probably  high  and  steep  land 
rising  from  a  deep  sea,  and  that  the  Caradoc  fossils,  some  of  them  of  lit- 
toral aspect,  as  Littorina  and  Turritella,  were  deposited  round  the  mar- 
gin of  that  ancient  land.  It  was  also  remarked  that  while  the  sandstone 
and  conglomerate  of  this  upper  Caradoc*  reposed  unconformably  on  the 
Llandeilo  beds,  it  at  the  same  time  graduated  upwards,  as  Sir  K.  Murchi- 
son  had  stated,  into  the  Wenlock  Shale. 

Subsequently  Professor  Sedgwick  and  Mr.  M'Coy,  pursuing  their  inves- 
tigations independently  of  the  Survey  in  North  Wales,  became  convincedf 
that  the  Caradoc  beds  of  May  Hill  and  the  Malverns,  constituting  the 
Upper  Caradoc,  already  mentioned,  were  full  of  Upper  Silur  an  fossils ; 
and  that  the  strata  of  Caradoc  sandstone  at  Horderly  and  other  places 
east  of  Caer  Caradoc  belonged  to  the  Bala  group  (or  equivalent  of  the 
Llandeilo),  being  distinguished  by  Lower  Silurian  species.  This  opinion 
was  finally  substantiated  by  Mr.  Salter  and  Mr.  Aveline,  in  1853,  by  an 
appeal  to  parts  of  Shropshire  where  "  the  Caradoc"  had  been  originally 
studied  by  Sir  E.  Murchison,  and  where  they  found  the  Upper  Caradoc 
unconformable  on  the  lower,  and  filled  with  a  series  of  very  distinct 
fossils.^ 

In  the  restricted  sense,  therefore,  in  which  it  is  now  understood,  the 
Caradoc  Sandstone  comprises  a  series  of  beds  of  passage  from  the  Lower 
to  the  Upper  Silurian  group.  It  is  everywhere  characterized  by  species 
of  Pentamerus  and  Atrypa  unknown  in  the  overlying  Wenlock  or  Lud- 
low  beds,  but  which  descend  into  the  strata  of  the  Llandeilo  group.  Pen- 
tamerus Icevis  (fig.  589),  and  P.  ollongus  may  be  particularly  mentioned 

Fig.  589. 


Pentamerus  Icevis,  Sow.    Caradoc  Sandstone. 
Perhaps  the  young  of  Pentamerus  oblongus. 
«,  I.  Views  of  the  shell  itself,  from  figures  in  Murchison's  Sil.  Syst 

c.  Cast  with  portion  of  shell  remaining,  and  with  the  hollow  of  the  central  septum  filled  with  spar. 

d.  Internal  cast  of  a  valve,  the  space  onco  occupied  by  the  septum  being  represented  by  a  hol- 

low in  which  is  seen  a  cast  of  the  chamber  within  the  septum. 

*  Quart.  Geol.  Journ.  vol.  iv.  p.  29 7.  f  Geol.  Quart.  Journ.  1852. 

i  Geol.  Quart.  Journ.  vol.  x.  p.  62. 


CH.  XXVIL]  LOWER  SILURIAN  ROCKS.  439 

as  brachiopods  which  abounded  in  Siluria,  and  had  a  very  wide  geo- 
graphical range,  being  met  with  in  the  same  place  in  the  Silurian  series 
of  Russia  and  the  United  States.  Among 
its  fossils,  too,  Tentaculites  annulatus  (fig.  ^f^^^^Bf^ ' 
590),  an  annelid  probably  allied  to  Ser- 
pula,  is  exceedingly  common.  This  also 
is  a  link  to  connect  it  with  the  Lower 
rather  than  the  Upper  Silurian.  All  the 
shelly  sandstone  of  the  Malvern  and  Ab- 
berly  Hills,  of  Tortworth  in  Gloucester- 

shire,  and   of  the   centre   of  the   May  Hill  Eastnor  Park ;  nat.  size  and  mag- 

and   Woolhope   districts  belong   to    this 

Middle  Silurian,  which  in  the  Malvern  range  attains  a  thickness  of  600 
feet.  Of  the  same  age  are  dense  masses  of  sandstone  with  stale,  2000 
feet  in  thickness,  in  the  higher  and  disturbed  regions  of  North  Wales,  as 
in  the  Berwyn  Mountains  for  example.  According  to  Professor  Sedg- 
wick  the  hard  quartzose  Coniston  Grits  of  Westmoreland  may  also  he 
referred  to  the  same  period. 

LOWER    SILURIAN    ROCKS. 

Llandeilo  Flags. — The  Lower  Silurian  strata  were  originally  divided 
oy  Sir  R.  Murchison  into  an  upper  group,  already  described,  and  termed 
the  Caradoc  Sandstone,  and  a  lower  one,  called,  from  a  town  in  Caer- 
marthenshire,  the  Llandeilo  Flags.  The  strata  last  mentioned  consist  of 
dark-colored  micaceous  flags,  frequently  calcareous,  with  a  great  thickness 
of  shales,  generally  black,  below  them.  The  same  beds  are  also  seen  a 
Builth  in  Radnorshire,  and  here  they  are  interstratified  with  rolcanic 
matter.  Above  these  typical  Llandeilo  beds,  however,  the  Lower  Silurian 
contains,  both  in  North  and  South  Wales,  some  strata  in  which  the 
Pentameri  of  the  Middle  Silurian,  already  alluded  to  (p.  438),  are  asso- 
ciated with  species  of  fossils  identical  with  those  in  the  Llandeilo  flags. 
The  corals  of  the  calcareous  zone  of  the  Llandeilo  belong  to  the  genera 
Holy 'sites  (see  fig.  579),  Helioliles,  Petraia,  Stenopora,  Favosites  (fig. 
580),  and  others  ;*  and  there  are  peculiar  Crinoids  and  Cystideans  in  the 
same  rocks.  These  last  are  amongst  the  most  recent  additions  made  by 
paleontologists  to  the  Radiata.  Their  structure  and  relations  were  first 
elucidated  in  an  essay  published  by  Von  Buch  at  Berlin  in  1845.  They 
are  the  Sphceronites  of  old  authors,  and  are  usually  met  with  as  spheroidal 
bodies  covered  with  polygonal  plates,  with  a  mouth  on  the  upper  side, 
and  a  point  of  attachment  for  a  stem  (which  is  almost  always  broken  off) 
on  the  lower  (fig.  591,  6).  They  are  considered  by  Professor  E.  Forbes 
as  intermediate  between  the  crinoids  and  echinoderms.  The  Spha3ronite 
here  represented  (fig.  591)  occurs  in  the  Llandeilo  beds  in  Wales,f  as 
also  in  Sweden  and  Russia. 

Examples  are  not  wanting,  though  very  rare,  of  star-fish  in  the  same 

*  Murchison's  Siluria,  p.  178. 

f  Quart.  Geol.  Journ.  vol.  vii.  p.  11 ;  and  Mem.  Geol.  Surv.  vol.  ii.  p.  518. 


140 


LOWER  SILURIAN  ROCKS. 


[On.  XXVII. 


beds.  Brachiopod  shells  are  in  the  greatest 
abundance,  chiefly  of  the  genera  Orthis, 
Leptcena,  and  Strophomena  (fig.  591).  Of 
the  Orthides,  those  species  with  broad  simple 
ribs  (fig.  592)  are  particularly  characteristic. 
Such  shells  as  Atrypa  and  Spirifer,  so  fre- 
quent in  the  Upper  and  Middle  Silurian,  are 
rare  or  confined  to  the  superior  part  of  the 
Lower  Silurian,  while  Chonetes  and  Produc- 
tus  are  wholly  absent.  It  is  remarkable, 
however,  that  Rhynchonella  and  Lingula, 
genera  of  which  there  are  living  representa- 
tives in  the  present  seas,  were  common  in 
the  Silurian  ocean. 


EcMnospTicerites  baltieus,  Eich- 
wald,  sp.    (Of  the  family  Cys- 
tidece.) 
a.  Mouth. 
&.  Point  of  attachment  of  stem. 

Lower  Silurian,  S.  and  N.  Wales. 


Fig.  592. 


"Tig.  598. 


Fig.  594. 


Ortliis  tricenaria, 

Hall. 

New  York.    Canada. 
£  nat.  size. 


Orthis  vespertilio,  Sow. 
Shropshire  ;  N.  and  S. 

Wales. 
%  nat.  size. 


Strophomena  (Orthis)  grandis,  Sowerby. 

§  nat.  size. 

Horderly,  Shropshire ;  also  Coniston, 
Lancashire. 


Among  the  Cephalopoda  are  Orthoceratites,  with  the  siphuncle  of 
large  dimensions  and  placed  on  one  side;  also  Lituites  (see  fig.  577), 
Bellerophon  (see  p.  407),  and  some  of  the  floating  tribes  of  mollusca 
(Pteropods).  The  Crustaceans  were  plentifully  represented  by  the  Trilo- 
bites,  which  appear  to  have  swarmed  in  the  Silurian  seas  just  as  crabs 
and  shrimps  do  in  our  own.  The  genera  Asaphus  (fig.  595),  Ogygia 
(fig.  596),  and  Trinucleus  (figs.  597  and  598)  are  especially  characteristic 


Fig.  595. 


Fig.  596. 


Asaphus  tyrannus,  Murch. 
Llandeilo ;  Bishop's  Castle,  &c. 


Ogygia  Buchii,  Burm.  (Asaphus 
JBuchii,  Brongn.) 

Builth,  Radnorshire ;  Llandeilo,  Caermarthenshire. 


CH.  XXVIL] 


LLANDEILO  FLAGS. 


of  strata  of  this  age,  if  not  entirely  confined  to  them  ;  but  very  numerous 
other  genera  accompany  these.  Burmeister,  in  his  work  on  the  organi- 
zation of  trilobites,  supposes  them  to  have  swum  at  the  surface  of  the 
water  in  the  open  sea  and  near  coasts,  feeding  on  smaller  marine  animals, 
and  to  have  had  the  power  of  rolling  themselves  into  a  ball  as  a  defence 
against  injury.  He  was  also  of  opinion  that  they  underwent  various 
transformations  analogous  to  those  of  living  crustaceans.  M.  Barrande, 
author  of  an  admirable  work  on  the  Silurian  rocks  of  Bohemia,  confirms 
the  doctrine  of  their  metamorphosis,  having  traced  more  than  twenty 
species  through  different  stages  of  growth  from  the  young  state  just  after 
its  escape  from  the  egg  to  the  adult  form.  He  has  followed  some  of  them 
from  a  point  in  which  they  show  no  eyes,  no  joints  to  the  body,  and  no 
distinct  tail,  up  to  the  complete  form  with  the  full  number  of  segments. 
This  change  is  brought  about  before  the  animal  has  attained  a  tenth  part 
of  its  full  dimensions,  and  hence  such  minute  and  delicate  specimens  arc 
rarely  met  with.  Some  of  his  figures  of  the  metamorphoses  of  the  com- 
mon Trinucleus  are  copied  in  the  annexed  wood-cuts  (figs.  ,597,  598). 

Fig.  593. 


Young  individuals  of  Trinucleus  con- 
centricu*  (T.  ornatus,  Barr.) 

a.  Youngest    state.     Natural    size   and 

magnified ;  the  body  rings  not  at  all 
developed. 

b.  A  little  older.    One  thorax  joint. 

c.  Still  more  advanced.    Three  thorax 

joints.  The  fourth,  fifth,  and  sixth 
segments  are  successively  produced, 
probably  each  time  the  animal  moult- 
ed its  crust 


Trinucleus  concentricus,  Eaton. 
Syn.  T.  caractaci,  Murch. 

N.  Ireland;  "Wales;  Shropshire;  N.  America; 
Bohemia. 


A  still  lower  part  of  the  Llandeilo  or  Bala  rocks  consists  of  a  black 
carbonaceous  slate  of  great  thickness,  frequently  containing  sulphate  of 
alumina  and  sometimes,  as  in  Dumfriesshire,  beds  of  anthracite.  It  has 
been  conjectured  that  this  carbonaceous  matter  may  be  due  in  great 
measure  to  large  quantities  of  imbedded  animal  remains,  for  the  number 
of  Graptolites  included  in  these  slates  was  certainly  very  great.  I  col- 
lected these  same  bodies  in  great  numbers  in  Sweden  and  Norway  in 
1835-6,  both  in  the  higher  and  lower  graptolitic  shales  of  the  Silurian 
system ;  and  was  informed  by  Dr.  Beck  of  Copenhagen,  that  they  were 
fossil  zoophytes  related  to  theVirgularia  and  Pennatula,  genera  of  which 
the  living  species  now  inhabit  mud  and  slimy  sediment.  The  most  emi- 
nent naturalists  still  hold  to  this  opinion. 


44:2 


THICKNESS  OF  SILUKIAN   STRATA.          [CH.  XXV1L 


Fig.  599. 


Fig.  600. 


Didymograpsus  geminus,  Hisinger,  sp. 
Sweden. 


a,  Z>.  Didymoffrapsus  (Graptolited)  Hur- 
chisoiiii,  Beck. 

Llandeilo  Flags.    "Wales. 

Fig.  601. 


Fig.  602. 


Diplogr 


rapsus  folium, 
isinger. 


Scotland;  Sweden. 


Fig.  603. 


Diplo(jrapsus  pristis, 
Hisinger,  sp. 

Shropshire;  Wales;  Sweden, 
&c. 


Rastrites  peregrinus,  Barrande. 
Scotland;  Bohemia;  Saxony. 


Beneath  the  black  slates  above  described  no  graptolites  appear  as  yet 
to  have  been  found,  but  the  characteristic  shells  and  trilobites  of  the 
Lower  Silurian  rocks  are  still  traceable  downwards,  in  North  and  South 
Wales,  through  a  vast  depth  of  shaly  beds,  interstratified  with  trappean 
formations,  sometimes  not  less  in  their  aggregate  thickness  than  11,000 
feet.  Hence  the  total  thickness  of  the  beds  assigned  to  the  Lower  Si- 
lurian, or  the  Llandeilo  group  of  Murchison,  is  not  less  than  20,000  feet, 
and  the  Upper  Silurian  rocks  are  above  5000  feet  in  addition.  If  these 
beds  were  all  exclusively  of  sedimentary  origin  we  might  well  expect, 
from  the  analogy  of  other  parts  of  the  earth's  crust,  to  find  that  they 
must  be  referred  paleontologically  to  more  than  one  era ;  in  other  words, 
that  changes  in  animal  and  vegetable  life,  as  great  as  those  which  oc- 
curred in  the  course  of  several  such  periods  as  the  Devonian,  Carbonifer- 
ous, and  Permian,  would  be  found  to  have  taken  place  while  the  accumu- 
lation of  so  enormous  a  pile  of  rocks  was  effected.  But  in  volcanic  archi- 
pelagoes, as  in  the  Canaries  for  example,  we  see  the  most  active  of  all 
known  causes,  aqueous  and  igneous,  simultaneously  at  work  to  produce 
great  results  in  a  comparatively  moderate  lapse  of  time.  The  outpour- 
ing of  repeated  streams  of  lava, — the  showering  down  upon  land  and 
sea  of  volcanic  ashes, — the  sweeping  seaward  of  loose  sand  and  cinders, 
or  of  rocks  ground  down  to  pebbles  and  sand,  by  torrents  descending 
steeply  inclined  channels, — the  undermining  and  eating  away  of  long 
lines  of  sea-cliff  exposed  to  the  swell  of  a  deep  and  open  ocean, — above 
all,  the  injection,  both  above  and  below  the  sea-level,  of  sheets  of  melted 
matter  between  the  lavas  previously  formed  at  the  surface, — these  op- 
erations may  combine  to  produce  a  considerable  volume  of  superimposed 
matter,  without  there  being  time  for  any  extensive  change  of  species. 


CH.  XXVII]         SILURIAN  EQUIVALENTS  IN  EUROPE.  443 

Nevertheless,  there  would  seem  to  be  a  limit  to  the  thickness  of  stony 
masses  formed  even  under  such  favorable  circumstances,  for  the  analogy 
of  tertiary  volcanic  regions  lends  no  countenance  to  the  notion  that  sed-- 
imentary  and  igneous  rocks  25,000,  much  less  45,000  feet  thick,  like 
those  of  Wales,  could  originate, while  one  and  the  same  fauna  should 
continue  to  people  the  earth.  If,  then,  we  allow  that  25,000  feet  of 
matter  may  be  ascribed  to  one  system,  such  as  the  Silurian,  from  the  top 
of  "  the  Ludlow  "  to  the  base  of  "  the  Llandeilo  "  inclusive,  we  may  be 
prepared  to  find  in  the  next  series  of  subjacent  rocks,  the  commencement 
of  another  assemblage  of  species,  or  even  in  part  of  genera,  of  organic 
remains.  Such  appears  to  be  the  fact,  and  I  shall  therefore  conclude 
with  the  Llandeilo  beds,  the  original  base-line  of  Sir  R.  Murchison,  my 
account  of  the  Silurian  formations  in  Great  Britain,  and  proceed  to  say 
something  of  their  foreign  equivalents,  before  treating  of  rocks  older  than 
the  Silurian. 

It  would  lead  me  into  too  long  a  digression  to  attempt  to  follow  the 
Upper,  Middle,  and  Lower  Silurian  into  Scotland,  the  lake  country, 
Cornwall,  and  other  parts  of  the  British  Isles.  For  an  account  of  these 
rocks  in  Ireland,  the  reader  is  referred  to  Col.  Portlock's  Report  on  Ty- 
rone, to  the  writings  of  Mr.  Griffith  and  Prof.  M'Coy,  and  those  of  the 
officers  of  the  Government  Survey,  as  well  as  to  the  sketch  recently  given 
by  Sir  R.  I.  Murchison. 

When  we  turn  to  the  Continent  of  Europe,  we  discover  the  same 
ancient  series  occupying  a  wide  area,  but  in  no  region  as  yet  has  it  been 
observed  to  attain  great  thickness.  Thus,  in  Norway  and  Sweden,  the 
total  thickness  of  strata  of  Silurian  age,  is  scarcely  equal  to  1000  feet,* 
although  the  representatives  both  of  the  Upper  and  Lower  Silurian  of 
England  are  not  wanting  there,  and  even  some  beds  of  schist  have  been 
comprehended  which,  as  we  shall  hereafter  see,  lie  below  the  Llandeilo 
group.  In  Russia  the  Silurian  strata,  so  far  as  they  are  yet  known,  seem 
to  be  even  of  smaller  vertical  dimensions  than  in  Scandinavia,  and  they 
appear  to  consist  chiefly  of  Middle  and  Lower  Silurian,  or  of  a  lime- 
stone containing  Pentamerus  ollongus,  below  which  are  strata  with  fossils 
corresponding  to  those  of  the  Llandeilo  beds  of  England.  The  lowest 
rock  with  organic  remains  yet  discovered,  is  "  the  Ungulite,  or  Obolus 
grit "  of  St.  Petersburg,  probably  coeval  with  the  Llandeilo,  and  not  ex- 
hibiting any  of  those  peculiar  forms  which  distinguish  "  the  Lingula  flags  " 
of  Wales,  or  the  Bohemian  "primordial  fauna"  of  Barrande. 

The  shales  and  grits  near  St.  Petersburg,  above  alluded  to,  contain 
green  grains  in  their  sandy  layers,  and  are  in  a  singularly  unaltered  state, 
taking  into  account  their  high  antiquity.  The  prevailing  brachiopods 
consist  of  the  Obolus  or  Ungulite  of  Pander,  and  a  Siphonotetra  (see 
figs.  604,  605).  As  bearing  on  the  antiquity  of  this  formation,  it  is  in- 
teresting to  notice  that  both  genera  have  recently  been  found  in  our  own 
Dudley  limestone. 

*  Murchison's  Siluria,  p.  321. 


44A 


SILURIAN   STRATA   OF   UNITED   STATES.      [On.  XXVIL 


Shells  erf  the  lowest  known  Fossiliferous  Beds  in  Russia. 

Fig.  605. 

a 


Obolus 


Siphonotreta 

From  the  lowest  Silurian  Sandstone, 
grits,"  of  Petersburg. 

a.  Outside  of  perforated  valve. 

b.  Interior  of  same,  showing  the  termination  of 

the  foramen  within. 


Obolus  Apollinis,  Eichwald. 

From  the  same  locality, 
a.  Interior  of  the  larger  or  ventral  valve. 
&.  Exterior  of  the  upper  (dorsal)  valve. 
(Davidson.) 


Among  the  green  grains  of  the  sandy  strata  above  mentioned,  Pro- 
fessor Ehrenberg  has  recently  (1854)  announced  his  discovery  of  remains 
of  foraminifera.  These  are  casts  of  the  cells ;  and  amongst  five  or  six 
forms,  three  are  considered  by  him  as  referable  to  existing  genera  (e.  g., 
Textularia,  Rotalia,  and  Gruttulina). 

SILURIAN   STRATA    OF   THE   UNITED    STATES. 

The  position  of  some  of  these  strata,  where  they  are  bent  and  highly 
inclined  in  the  Appalachian  chain,  or  where  they  are  nearly  horizontal  to 
the  west  of  that  chain,  is  shown  in  the  section,  fig.  505,  p.  388.  But  these 
formations  can  be  studied  still  more  advantageously  north  of  the  same 
line  of  section,  in  the  States  of  New  York,  Ohio,  and  other  regions  north 
and  south  of  the  great  Canadian  lakes.  Here  they  are  found,  as  in  Russia, 
nearly  in  horizontal  position,  and  are  more  rich  in  well-preserved  fossils 
than  in  almost  any  spot  in  Europe.  In  the  State  of  New  York,  where  the 
succession  of  the  beds  and  their  fossils  have  been  most  carefully  worked 
out  by  the  Government  Surveyors,  the  subdivisions  given  in  the  first 
column  of  the  annexed  list  have  been  adopted. 

Subdivisions  of  the  Silurian  Strata  of  New  York.     (Strata  below  the 
Oriskany  Sandstone,  see  Table,  p.  426.) 

British  Equivalents. 


New  York  Names. 

1.  Upper  Pentamerus  Limestone 

2.  Encrinal  Limestone 

3.  Delthyris  Shaly  Limestone 

4.  Pentamerus  Limestone 

5.  Tentaculite  Limestone 

6.  Onondaga  Salt-group 

7.  Niagara  Group 

8.  Clinton  Group 

9.  Medina  Sandstone 

10.  Oneida  Conglomerate 

11.  Gray  Sandstone 

12.  Hudson  River  Group 

13.  Utica  Slate 

14.  Trenton  Limestone 

15.  Black- River  Limestone 

16.  Bird's-Eye  Limestone 

17.  Chazy  Limestone. 

18.  Calciferous  Sandstone 

19.  Potsdam  Sandstone 


Upper  Silurian    (or    Ludlow  and 
Wenlock  formations). 


I  Middle  Silurian  (or  Caradoc  Sand- 
j      stone). 

j-  Lower  Silurian  (or  Llandeilo  beds). 


j  Cambrian  ?  (or  Lingula   flags    and 
(      beds,  older  than  "  the  Llandeilo.") 

In  the  second  column  of  the  same  table  I  have  added  the  supposed 
British  equivalents.     All  paleontologists,  European  and  American,  such 


Cm  XXVII.]          SPECIFIC  AGKEEMEXT  OF  FOSSILS.  445 

as  MM.  de  Verneuil,  D.  Sharp,  Prof.  Hall,  and  others,  \vho  have  entered 
upon  this  comparison,  admit  that  there  is  a  marked  general  correspond- 
ence in  the  succession  of  fossil  forms,  and  even  species,  as  we  trace  the 
organic  remains  downwards  from  the  highest  to  the  lowest  beds  :  but  it  is 
impossible  to  parallel  each  minor  subdivision.  In  regard  to  the  three  fol- 
lowing points  there  is  little  difference  of  opinion. 

1st.  That  the  Niagara  Limestone,  No.  7,  over  which  the  river  of  that 
name  is  precipitated  at  the  great  cataract,  together  with  its  underlying 
shales,  corresponds  to  the  Wenlock  limestone  and .  shale  of  England. 
Among  the  species  common  to  this  formation  in  America  and  Europe  are 
Calymene,  JBlumenbachii,  Homalonotus  delphinocephalus  (fig.  587),  with 
several  other  trilobites  ;  Rhynchonella  Wilsoni,  and  It.  cuneata  ;  Orthis 
elegantula,  Pentamerus  galeatus,  with  many  more  brachiopods ;  Qrtho- 
ceras  annulatum,  among  the  cephalopodous  shells ;  and  Favosites  goth- 
landica,  with  other  large  corals. 

2d.  That  the  Clinton  Group,  No.  8,  containing  Pentamerus  oblongus 
and  P.  Icevis,  and  related  more  nearly  by  its  fossil  species  with  the  beds 
above  than  with  those  below,  is  the  equivalent  of  the  Middle  Silurian  as 
above  defined,  p.  437. 

3d.  That  the  Hudson  River  Group,  No.  12,  and  the  Trenton  Lime- 
stone, No.  14,  agree  paleontologically  with  the  Llandeilo  flags,  containing 
in  common  with  them  several  species  of  trilobites,  such  as  Asaphus  (Iso- 
telus)  gigas,  Trinucleus  concentricus  (fig.  598,  p.  441) ;  and  various 
shells,  such  as  Orthis  striatula,  Orthis  biforata  (or  0.  lynx),  0.  porcata 
( 0.  occidentals  of  Hall),  Bellerophon  bilobatus,  &c.* 

Mr.  D.  Sharpe,  in  his  report  on  the  inollusca  collected  by  me  from 
these  strata  in  North  America,f  has  concluded  that  the  number  of  species 
common  to  the  Silurian  rocks  on  both  sides  of  the  Atlantic  is  between  30 
and  40  per  cent. ;  a  result  which,  although  no  doubt  liable  to  future 
modification,  when  a  larger  comparison  shall  have  been  made,  proves 
nevertheless  that  many  of  the  species  had  a  wide  geographical  range. 
It  seems  that  comparatively  few  of  the  gasteropods  and  lamellibranchiate 
bivalves  of  North  America  can  be  identified  specifically  with  European 
fossils,  while  no  less  than  two-fifths  of  the  brachiopoda,  of  which  my  col- 
lection chiefly  consisted,  are  the  same.  In  explanation  of  these  facts,  it  is 
suggested  that  most  of  the  recent  brachiopoda  (especially  the  orthidiform 
ones)  are  inhabitants  of  deep  water,  and  that  they  may  have  had  a  wider 
geographical  range  than  shells  living  near  shore.  The  predominance  of 
bivalve  mollusca  of  this  peculiar  class  has  caused  the  Silurian  period  to  be 
sometimes  styled  "  the  age  of  brachiopods." 

The  calcareous  beds,  Nos.  15,  16,  17,  and  18,  below  the  Trenton  Lime- 
stone, have  been  considered  by  M.  de  Verneuil  as  Lower  Silurian,  because 
they  contain  certain  species,  such  as  Asaphus  (Isotelus)  gigas,  TUcenus 
crassicauda,  and  Orthoceras  bilineatum,  in  common  with  the  overlying 
Trenton  Limestone.];  But,  according  to  Professor  Hall,  the  Illcenus  was 

*  See  Murchison's  Siluria,  p.  414.  f  Quart.  Geol.  Journ.  voL  iv. 

\  Soc.  Geol.  France,  Bulletin,  vol.  iv.  p.  651,  1847. 


446  CANADIAN  EQUIVALENTS.  [Ca.  XXVII, 

erroneously  identified,  an  error  to  which  he  confesses  that  he  himself  con- 
tributed ;  and  on  the  whole  these  lower  beds  contain,  he  thinks,  a  very 
distinct  set  of  species,  only  three  or  four  of  them  out  of  eighty-three 
passing  upwards  into  the  incumbent  formations.* 

Be  this  as  it  may,  the  Black  River  Limestone,  No.  15,  contains  certain 
forms  of  Orthoceras  of  enormous  size  (some  of  them  8  or  9  feet  long !), 
of  the  subgenera  Ormoceras  and  Endoceras,  seeming  to  represent  the 
Lower  Silurian  or  Orthoceras  limestone  of  Sweden.  Moreover,  the  gen- 
eral facies  of  the  fauna  of  all  these  beds  is  essentially  similar.  Another 
ground  for  extending  our  comparison  of  the  Llandeilo  beds  of  Europe  as 
far  down  as  the  calciferous  sandstone  is  derived  from  the  researches  of 
Mr.  Logan  in  Canada,  and  the  study  by  Mr.  Salter  of  the  fossils  collected 
by  the  Canadian  Surveyor  near  the  S.  E.  end  of  the  Ottawa  River,  where 
one  mass  of  limestone  incloses  species  common  to  all  the  beds  from  the 
Calciferous  Sandstone  (No.  18)  up  to  the  Trenton  Limestone  (No.  14). 
In  this  rock,  the  Asaphus  gigas  and  other  well-known  Trenton  species  are 
blended  with  the  Maclurea  (a  left-handed  Euomphalus,  fig.  606),  a  genus 

Fossils  from  Allumette  Kapids,  River  Ottawa,  Canada, 
a  Fig.  606. 


Maclurea  Logani,  Salter. 
a.  View  of  the  shell.  &.  Its  curious  operculnm. 

characteristic  of  the  Chazy  Limestone,  or  No.  17  ;  Fis- 607- 

and  Murchisonia  gracilis  (fig.  607)  is  another 
Trenton  Limestone  species  found  in  the  same  Silu- 
rian limestone  of  Canada  ;j  while  one  of  the  most 
common  shells  in  it  is  the  Raphistoma  ?  (Euom- 
phalus)  uniangulatum,  Hall,  a  species  character- 
istic in  New  York  of  the  Calciferous  Sandstone 

itself.  Murchisonia  gracilis,  Hall. 

In  Canada,  as  in  the  State  of  New  York,  the  4ft 
Potsdam  Sandstone  underlies  the  above-mentioned  f  ?£*  roS! 
calcareous  rocks,  but  contains  a  different  suite  of 
fossils,  as  will  be  hereafter  explained.  In  parts  of  the  globe  still  more 
remote  from  Europe  the  Silurian  strata  have  also  been  recognized,  as  in 
South  America,  Australia,  and  recently  by  Captain  Strachey  in  India. 
In  all  these  regions  the  facies  of  the  fauna,  or  the  types  of  organic  life, 
enable  us  to  recognize  the  contemporaneous  origin  of  the  rocks  ;  but  the 
fossil  species  are  distinct,  showing  that  the  old  notion  of  a  universal  dif- 
fusion throughout  the  "  primaeval  seas"  of  one'  uniform  specific  fauna  was 

*  Hall ;  Forster  and  Whitney's  Report  on  Lake  Superior,  Pt.  II.  1851. 
\  Logan,  Report  Brit.  Assoc.  Ipswich,  pp.  59,  63. 


Cn.  XXVIL]  CAMBRIAN   GROUP.  447 

quite  unfounded,  geographical  provinces  having  evidently  existed  in  the 
oldest  as  in  the  most  modern  times.* 

Whether  the  Silurian  rocks  are  of  deep-water  origin. — The  grounds 
relied  upon  by  Professor  E.  Forbes  for  inferring  that  the  larger  part  of  the 
Silurian  Fauna  is  indicative  of  a  sea  more  than  70  fathoms  deep,  are  the 
following :  first,  the  small  size  of  the  greater  number  of  conchifera ; 
secondly,  the  paucity  of  pectinibranchiata  (or  spiral  univalves)  ;  thirdly, 
the  great  number  of  floaters,  such  as  Bellerophon,  Orthoceras,  &c. ; 
fourthly,  the  abundance  of  orthidifonn  brachiopoda ;  fifthly,  the  absence 
or  great  rarity  of  fossil  fish. 

It  is  doubtless  true  that  some  living  Terebratulae,  on  the  coast  of  Aus- 
tralia, inhabit  shallow  water ;  but  all  the  known  species,  allied  in  form  to 
the  extinct  Orthis,  inhabit  the  depths  of  the  sea.  It  should  also  be  re- 
marked that  Mr.  Forbes,  in  advocating  these  views,  was  well  aware  of  the 
existence  of  shores,  bounding  the  Silurian  sea  in  Shropshire,  and  of  the 
occurrence  of  littoral  species  of  this  early  date  in  the  northern  hemisphere. 
Such  facts  .are  not  inconsistent  with  his  theory ;  for  he  has  shown,  in 
another  work,  how,  on  the  coast  of  Lycia,  deep-sea  strata  are  at  present 
forming  in  the  Mediterranean,  in  the  vicinity  of  high  and  steep  land. 

Had  we  discovered  the  ancient  delta  of  some  large  Silurian  river,  we 
should  doubtless  have  known  more  of  the  shallow-water,  brackish-water, 
and  fluviatile  animals,  and  of  the  terrestrial  flora  of  the  period  under  con- 
sideration. To  assume  that  there  were  no  such  deltas  in  the  Silurian 
world,  would  be  almost  as  gratuitous  an  hypothesis,  as  for  the  inhabitants 
of  the  coral  islands  of  the  Pacific  to  indulge  in  a  similar  generalization 
respecting  the  actual  condition  of  the  globe. 

CAMBRIAN    GROUP. 

Upper  Cambrian. — We  have  next  to  consider  the  fossiliferous  strata 
that  occupy  a  lower  position  than  the  "  Llandeilo  beds,"  which  last  form, 
as  we  have  seen,  the  Lower  division  of  the  great  Silurian  series,  as  origi- 
nally defined  by  Sir  R.  Murchison.  In  the  Appendix  to  his  important 
work  before  cited,f  Sir  Roderick  has  given,  on  the  authority  of  Mr.  Salter, 
a  list  of  no  less  than  96  species  of  fossils  (of  which  specimens  have  been 
examined  either  by  himself  or  Professor  McCoy),  all  common  to  the 
Upper  and  Lower  Silurian  strata,  or,  in  other  words,  which,  being  found 
either  in  the  Ludlow  or  Wenlock  beds,  are  also  met  with  in  the  Llandeilo 
formation.  The  range  upwards  of  so  many  species  from  the  inferior  to 
the  superior  group  shows  that,  independently  of  the  link  supplied  by  the 
Caradoc  or  Middle  Silurian,  there  is  such  a  connection  between  the  two 
principal  divisions,  as  makes  it  natural  to  assign  the  whole  to  one  great 
period.  To  attempt,  therefore,  to  give  a  new  name  to  the  Llandeilo  beds, 
or  to  call  them  Cambrian,  as  has  been  recently  proposed  by  some  geol- 
ogists, would  be  to  act  in  violation  of  the  ordinary  rules  of  classifica- 

*  E.  Forbes,  Anniv.  Address,  1854,  Quart.  Journ.  GeoL  Soc.  voLx.  p.  88. 
f  Siluria,  p.  485. 


448 


LINGULA  FLAGS  OF  NORTH  WALES.        [On.  XXVII. 


tion,  and  would  create  much  confusion,  by  disturbing  a  nomenclature 
long  received  and  originally  established  on  well-defined  paleontological 
data. 

In  Shropshire,  the  classical  region,  where  the  type  of  the  Silurian 
group  was  first  made  out  by  Murchison,  the  formations  subjacent  to 
the  Llandeilo  consisted  of  quartzose  rocks,  sterile  of  fossils,  or  yielding 
little  more  than  some  obscure  fucoids.  In  North  Wales,  Professor  Sedg- 
wick  found  below  the  Bala  Limestone,  long  since  recognized  as  the 
equivalent  of  the  Llandeilo  flags,  a  vast  thickness  of  sedimentary  and 
volcanic  rocks,  the  lithological  characters  and  physical  features  of  which 
he  studied  assiduously  for  years,  dividing  them  into  well-marked  forma- 
tions, to  which  he  affixed  names.  Collectively  they  constituted  the  chief 
part  of  the  rocks  called  by  him  "  Cambrian."  They  were  devoid  of  lime- 
stone ;  but  in  a  group  of  micaceous  sandstones  Mr.  E.  Davis  discovered 
in  1846  the  Lingula  named  after  him,  and  from  which  the  name  of 
"Lingula  flags"  has  since  been  denved.  In  these  flags,  about  1500  or 
2000  feet  in  thickness,  several  other  fossils  were  afterwards  found,  of  dif- 
ferent species  from  those  in  the  Llandeilo  beds.  Amongst  them,  trilo- 
bites,  Agnostus  and  Conocephalus  (for  genus,  see  fig.  614),  and  some  rare 
Brachiopoda  and  Bryozoa,  still  unpublished  by  our  Government  survey- 
ors, have  been  detected,  and  in  the  inferior  black  slates  of  North  Wales  a 
trilobite  called  Paradoxides  (for  genus,  see  fig.  613),  a  form  still  more 
characteristic  of  this  era,  together  with  another  of  the  genus  Olenus  (fig. 
610),  and  a  phyllopod  crustacean  (fig.  608). 

Fossils  of  the  "  Lingula  Flags"  or  lowest  Fossiliferous  Hocks  of  Britain, 

Fig.  609.  Fig.  610. 


Hymenocaris  vermicauda, 

Salter. 

A  Phyllopod  Crustacean. 
|  nat.  size. 

"Lingula  Flags"  of  Dolgelly,  and  Ffestiniog;  N.  Wales. 


Lingula  Davisii,  M'Coy. 

a.  £  natural  size. 

&.  Distorted  by  cleavage. 


Olenus  mierurus, 

Salter- 
i  nat.  size. 


I  have  before  observed,  that  between  the  Bala  Limestone  and  the 
Lingula  Flags  there  is  a  thickness  of  11,000  feet  of  strata,  in  which 
Graptolites  and  certain  species  of  Asaphus,  Calymene,  and  Oyygia 
occur.  These  may  be  referred  at  present  to  the  Silurian  series,  but 
the  exact  limits  between  them  and  the  Lingula  Flags  cannot  yet  be 
assigned. 

We  might  have  anticipated,  as  already  remarked,  p.  442,  that,  when- 
ever a  fossil  Fauna  was  discovered  in  the  Cambrian  strata,  it  would  be 
found  to  consist  of  distinct  species,  and  even,  to  a  large  extent,  of  distinct 
genera  ;  for,  although  geological  periods  are  of  very  unequal  value  in 
regard  to  the  lapse  of  time  (see  p.  103),  and  our  lines  of  separation  may 


CH.  XXVII. ]  LOWER   CAMBRIAN.  449 

often  be  somewhat  arbitrary,  yet  in  no  part  of  the  world  have  we 
hitherto  examined  a  succession  of  rocks  having  so  great  a  thickness  as 
45,000  feet,  even  where  they  are  made  up  in  part  of  volcanic  materials, 
which  have  been  referred  to  one  period  as  being  characterized  by  one  and 
the  same  fauna. 

The  first  formation  mentioned  by  Prof.  Sedgwick,  beneath  the  Bala 
Limestone  (and  its  associated  beds  of  sandstone)  in  N.  Wales,  are  certain 
beds,  7000  feet  thick,  called  the  Arenig  slates  and  porphyry.  Under 
them  he  finds  theTremadoc  Slates,  1000  feet  thick,  and  next  theLingula 
Flags,  already  described,  1500  feet  or  more,  which,  in  accordance  with 
views  first  put  forward  by  Mr.  Salter,  I  have  referred  provisionally  to  an 
Upper  Cambrian  group. 

Lower  Cambrian. — To  the  Lingula  Flags  last  enumerated,  another 
series,  called  by  Prof.  Sedgwick  the  Bangor  Group,  succeeds  in  the  de- 
scending order,  comprising,  first,  the  Harlech  Grits,  500  feet  thick,  and 
next  the  Llanberis  Slates,  1000  feet.  These  formations  have  as  yet  proved 
barren  of  organic  remains  in  N.  Wales ;  but  in  Ireland,  immediately 
opposite  Anglesea  and  Caernarvon,  rocks  of  the  same  mineral  character 
as  the  Bangor  Group,  and  occupying  precisely  the  same  place  in  the 
geological  series,  have  afforded  two  species  of  zoophytes,  to  which  Pro- 
fessor Forbes  has  given  the  name  of  Oldhamia  (figs.  611  and  612).  The 
position  of  these  rocks  has  been  decided  by  the  Government  Surveyors, 

The  most  Ancient  Fossils  yet  known  (1854). 
Fig.  (511. 


Oldhamia  radiata,  Forbes. 
Wicklow,  Ireland. 


Oldhamia  antiqua,  Forbes. 
Wicklow,  Ireland. 

and  confirmed  by  Sir  R.  Murchison,  so  that  here  we  behold  the  relics  of 
the  most  ancient  organic  bodies  yet  known.  We  are  of  course  unable  at 
present  to  determine  whether  they  belong  to  the  same  fauna  as  the  fossils 
of  the  "  Lingula  Flags,"  or  to  an  older  one.  The  beds  containing  them 
may  provisionally  be  called  Lower  Cambrian,  for  it  will  always  happen 
that  our  inquiries  will  terminate  downwards  in  rocks  affording  very  im- 
perfect materials  for  classification.  This  will  continue  to  be  the  case, 
however  many  steps  we  may  make  in  future  in  penetrating  into  the  re- 
moter annals  of  the  past. 

29 


450 


PKIMOEDIAL   GKOUP   OF  BOHEMIA.          [Cn.  XXVII 


Bohemia. — M.  Barrande,  in  his  admirable  monograph  on  the  Paleozoic 
rocks  of  Bohemia,  has  laid  much  stress  on  the  distinctness  and  isolation 
of  what  he  calls  the  "Protozoic  schists,"  which  attain  a  thickness  of  120C 
feet,  and  lie  at  the  base  of  the  whole  Silurian  group,  as  defined  by  him, 
These  schists  have  no  limestone  associated  with  them,  and  are  regarded 
by  M.  Barrande  as  contemporaneous  with  the  "  Lingula  Flags"  of  N. 
Wales.  So  far  as  he  has  yet  carried  his  researches,  this  "  primordial 
fauna,"  as  he  designates  it,  has  yielded  scarcely  any  other  fossils  than 
Trilobites,  the  other  animal  remains  consisting  of  a  Pteropod,  some  Cys- 
tideee,  and  an  Orthis,  all  of  new  and  peculiar  species.  Of  the  Trilobites, 
even  the  genera,  with  the  exception  of  one  (Agnostus,  figs.  615  and  616), 
are  peculiar.  These  genera  are  Paradoxides  (see  fig.  613),  of  which 
there  are  no  less  than  twelve  species,  Oonocephalus  (fig.  614),  Ellipso 

Fossils  of  the  lowest  Fossiliferous  Beds  in  Bohemia^  or  "  Primordial  Zone  "  of  Barrande. 
Fig.  613.  Fie.  614. 


Conocfphtdux  fitriatux,  Emmrieh. 

£  nat.  size. 
Ginetz  and  Skrey. 


Paradoxides  Bohemicus,  Barr. 

About  one-third  natural  size. 
"Lowest    Silurian  Beds"    of 

Ginetz,  Bohemia. 
(Etage  C.  of  Barrande.) 

Fig.  617. 


Fig.  615. 


Aflnostus  integer,  Beyrich. 
Nat.  size  and  magnified. 


Fig.  616. 


Agnostus  Rem,  Barr. 

Nat.  size,  Skrey. 


cephalus,  Sao  (fig.  617),  Arionellus,  and 
Hydrocephalus.    They  have  all  a  facies  of 
their  own,  dependent  on  the  multiplication 
of  their  thoracic  segments,  and  the  dimi- 
nution of  their  caudal  shield  or  pygidium. 
All  the  Bohemian  species  differ  as  yet 
,     ,,        a  from  any  found  in  England,'  which  may 

Sao  nirmtta,  Barrande,  in    its  various  *  * 

stages  of  growth.   Skrey.  be  owing  chiefly  to  the  very  small  num- 

The  small  lines   beneath    indicate   the    ,  ,  ,  •      /-<        ,  -r>  •     • 

true  size,   in  the  youngest  state,  a,   ber  as  yet  known  in  brreat  13ntam  ;  or  it 

may  be  due  entirely  to  the  influence  of 
geographical  causes.  It  seems,  neverthe- 
]ess  to  confirm  the  view  here  taken  of  the 

'. 

"primordial  zone"  being  characterized 
by  fossils  distinguishable  from  the  Llandeilo,  or  Lower  Silurian  group  ; 
because  the  other  and  higher  Silurian  formations  of  Barrande  have  each 
of  them  many  species  in  common  with  the  successive  subdivisions  of  the 
British  series. 


5&  ^ 

but  the  facial  sutures  are  not  com- 

pleted  ;  at  e  the  full-grown  animal,  half 

its  true  size,  is  shown. 


C.T.  XXVII.]        POTSDAM   SAXDSTOXE    OF   X.   AMERICA.  451 

One  of  the  so-called  "  primordial"  Trilobites  of  the  genus  Sao,  a  form 
not  found  as  yet  elsewhere  in  the  world,  has  afforded  M.  Barrande  a  fine 
illustration  of  the  metamorphosis  of  these  creatures ;  for  he  has  traced 
them  through  no  less  than  twenty  stages  of  their  development.  A  few 
of  these  changes  have  been  selected  for  representation  in  the  accompany- 
ing figures,  that  the  reader  may  learn  the  gradual  manner  in  which  differ- 
ent segments  of  the  body  and  the  eyes  make  their  appearance.  When 
we  reflect  on  the  altered  and  crystalline  condition  usually  belonging  to 
rocks  of  this  age,  and  how  devoid  of  life  they  are  for  the  most  part  in 
North  Wales,  Ireland,  and  Shropshire,  the  information  respecting  such 
minute  details  of  the  Natural  History  of  these  crustaceans,  as  is  supplied 
by  the  Bohemian  strata,  may  well  excite  our  astonishment,  and  may  rea- 
sonably lead  us  to  indulge  a  hope  that  geologists  may  one  day  gain  an 
insight  into  the  condition  of  the  planet  and  its  inhabitants  at  eras  long 
antecedent  to  the  Cambrian ;  for  those  parts  of  the  globe  which  have 
been  subjected  to  a  scrutiny  as  rigorous  as  North  Wales  and  Bohemia 
are  insignificant  spots,  and  we  are  every  day  discovering  new  areas,  es- 
pecially in  the  United  States  and  Canada,  where  beds  as  old  as  the 
"  primordial  schists,"  or  older,  may  be  studied. 

Sweden  and  Norway. — The  Lingula  Flags  of  North  Wales,  and  the 
"  primordial  schists"  of  Bohemia,  are  represented  in  Sweden  by  strata, 
the  fossils  of  which  have  been  described  by  an  able  naturalist,  M.  An- 
gelin,  in  his  "  Pateontologica  Suecica  (1852-4)."  The  "alum  schists," 
as  they  are  called  in  Sweden,  resting  on  a  fucoid-sandstone,  contain 
trilobites  belonging  to  the  genera  Paradoxides,  Olenus,  Agnostus,  and 
others,  some  of  which  present  rudimentary  forms,  like  the  genus  last 
mentioned,  without  eyes,  and  with  the  body  segments  scarcely  de- 
veloped, and  others  again  have  the  number  of  segments  excessively  mul- 
tiplied, as  in  Paradoxides.  These  peculiarities  agree  with  the  characters 
of  the  crustaceans  met  with  in  the  Upper  Cambrian  strata,  before  men- 
tioned. 

United  States  and  Canada. — In  the  table,  at  p.  444, 1  have  already 
pointed  out  the  relative  position  of  the  Potsdam  Sandstone,  which  has 
long  been  known  as  the  lowest  fossil iferous  formation  in  the  United  States 
and  Canada.  I  have  seen  it  on  the  banks  of  the  St.  Lawrence  in  Canada, 
and  on  the  borders  of  Lake  Champlain,  where,  as  at  Keesville,  it  is  a  white 
quartzose  fine-grained  grit,  almost  passing  into  quartzite.  It  is  divided 
into  horizontal  ripple-marked  beds,  very  like  those  of  the  Lingula  flags  of 
Britain,  and  replete  with  a  small  round-shaped  Lingula  in  such  numbers 
as  to  divide  the  rock  into  parallel  planes,  in  the  same  manner  as  do  the 
scales  of  mica  in  some  micaceous  sandstones.  This  formation,  as  we  learn 
from  Mr.  Logan,  is  TOO  feet  thick  in  Canada ;  the  lower  portion  consisting 
of  a  conglomerate  with  quartz  pebbles ;  the  upper  part  of  sandstone  con- 
taining fucoids,  and  perforated  by  small  vertical  holes,  which  are  very 
characteristic  of  the  rock,  and  appear  to  have  been  made  by  annelids 
(Scolitkus  linearis). 

On  the  banks  of  the  St.  Lawrence,  near  Beauharnois  and  elsewhere, 


452  FOOTPRINTS  NEAR  MONTREAL.  [Cn.  XXVII 

many  fossil  footprints  have  been  observed  on  the  surface  of  its  rippled 
layers.  These  impressions  were  first  noticed  by  Mr.  Abraham,  of  Mon- 
treal, in  1847,  and  were  supposed  to  be  tracks  of  a  tortoise;  but 
Mr.  Logan  has  since  brought  some  of  the  slabs  to  London,  together 
with  numerous  casts  of  other  slabs,  enabling  Professor  Owen  to  cor- 
rect the  idea  first  entertained,  and  to  decide  that  they  were  not  due 
to  a  chelonian,  nor,  as  he  imagines,  to  any  vertebrate  creature.  The 
Hunterian  Professor  inclines  to  the  belief  that  they  are  the  trails  of 
more  than  one  species  of  articulate  animal,  probably  allied  to  the  King 
Crab,  or  Limulus.  Between  the  two  rows  of  foot-tracks  runs  an  im- 
pressed median  line  or  channel,  supposed  by  the  professor  to  have 
been  made  by  a  caudal  appendage  rather  than  by  a  prominent  part 
of  the  trunk.  Some  individuals  appear  to  have  had  three,  and  others 
five  pairs,  of  limbs  'used  for  locomotion.  The  width  of  the  tracks  be- 
tween the  outermost  impressions  varies  from  3j  to  5^  inches,  which 
would  imply  a  creature  of  much  larger  dimensions  than  any  organic  body 
yet  obtained  from  strata  of  such  antiquity.  Their  size  alone  is  therefore 
important,  as  warning  us  of  the  danger  of  drawing  any  inference,  from 
mere  negative  evidence,  as  to  the  extreme  poverty  of  the  fauna  of  the 
earlier  seas. 

Mr  ."Logan  informs  us,*  that  the  Lower  Silurian  strata  and  the  Potsdam 
Sandstone  in  Canada  rest  unconformably  on  a  still  older  series  of  aqueous 
rocks,  which,  as  he  says,  may  be  Cambrian  (Lower  Cambrian,  or,  perhaps, 
still  older  ?),  and  which  include  conglomerates  and  beds  of  limestone.  In 
both  of  these,  nodules  of  phosphate  of  lime  are  frequently  observed.  That 
these  contorted  rocks  are  of  aqueous  origin,  he  infers  from  the  presence  of 
quartz  pebbles  in  the  conglomerates.  Together  with  the  associated  igne- 
ous masses,  this  ancient  series  attains  a  thickness  of  at  least  10,000  feet, 
in  the  Lake  Huron  district,  and  includes  the  copper-bearing  rocks  of  that 
part  of  Canada.  Below  these  again  lies  gneiss,  with  interstratified  marble, 
in  which  crystals  of  phosphate  of  lime  both  large  and  small  are  not  un- 
common. This  phosphate,  as  Mr.  Logan  suggests,  may  have  "  a  possible 
connection  with  life  in  those  ancient  rocks." 

In  the  frontispiece  to  this  volume,  and  in  fig.  83,  p.  59,  the  reader  may 
refer  to  a  section  on  the  coast  of  Scotland  where  the  Devonian  strata  lie 
unconformably  on  the  highly  inclined  Silurian  schists,  and  I  have  cited 
the  eloquent  reflections  of  Playfair  when  he  looked,  with  his  teacher 
Hutton,  "  so  far  into  the  abyss  of  time."  But  in  the  lake  district  of  N. 
America,  the  Potsdam  Sandstone,  forming  the  upper  or  horizontal  series, 
is  older  than  even  the  inclined  strata  of  St.  Abb's  Head  in  Scotland.  In 
Canada  again,  we  behold  the  monuments  of  still  another  period  in  the 
remote  distance,  attesting,  as  Playfair  exclaimed,  "  how  much  farther  the 
reason  may  go  than  the  imagination  can  venture  to  follow." 

Valley  of  the  Upper  Mississippi.  Mr.  Dale  Owen  has  recently  pub- 
lished a  graphic  sketch,  in  his  survey  of  Wisconsin  (1852),  of  the  lowest 

*  Quart.  Geol.  Journ.  vol.  viii.  p.  210. 


CH.  XXVIL]         PERIOD   OF   INVERTEBRATE   ANIMALS. 


453 


Fig.  618. 


sedimentaiy  rocks  near  the  head-waters  of  the 
Mississippi,  lying  at  the  base  of  the  whole 
Silurian  series.  They  are  many  hundred  feet 
thick,  and  for  the  most  part  similar  in  char- 
acter to  the  Potsdam  Sandstone  above  de- 
scribed, but  including  in  their  upper  portions 
intercalated  bands  of  magnesian  limestone,  and 
in  their  lower  some  argillaceous  beds.  Among 
the  shells  of  these  strata  are  species  of  Lingula 
ind  Orthis,  and  several  trilobites  of  the  new 
genus  Dikelocephalus  (fig.  618).  These  rocks, 
occurring  in  Iowa,  Wisconsin,  and  Minnesota,  Dikdocephai 

,       .       ,    ,  ,    T    i  Dale  Owen,    i  diameter. 

seem  destined  hereafter  to  throw  great  light    A  large  crustacean  of  the  oienoid 


on  the  state  of  organic  We  in  the  Cambrian 

period.     Six  beds  containing  trilobites,  sepa-       Mississippi. 

rated  by  strata  from  10  to  150  feet  thick,  are  already  enumerated. 

Relation  of  Silurian  and  Cambrian  Faunas.  —  That  there  is  a  con- 
siderable connection  between  the  Cambrian  and  lower  Silurian  faunas, 
notwithstanding  that  nearly  every  species  may  be  distinct,  seems  evident  ; 
but  it  may  not  be  a  closer  one  than  that  existing  between  the  Upper 
Silurian  and  Devonian.  This  I  infer  from  the  following  facts,  —  that  in 
Bohemia,  where  the  Cambrian  or  primordial  fauna  of  Barrande  is  best 
developed,  it  consists  mainly  of  Trilobites  ;  and  of  this  order  more  than 
two-thirds  of  the  genera  and  all  the  species,  more  than  twenty  in  number, 
are,  with  one  exception  (Agnostus  pisiformis),  distinct  from  the  Silurian. 
But  M.  Barrande  observes  that  out  of  thirty-nine  Silurian  genera  of 
Trilobites,  no  less  than  eleven  pass  upwards  into  the  Devonian.  If,  there- 
fore, we  had  only  trilobites  in  the  latter,  its  generic  relationship  to  the 
Silurian  fauna  would  appear  greater  than  that  of  the  Silurian  to  the  Cam- 
brian. And,  though  the  details  of  the  English  rocks  of  this  age  are  not 
yet  fully  known,  the  species  at  least  appear  all  to  be  distinct.  The  same 
holds  good  with  regard  to  the  fossils  of  the  Swedish  strata,  and,  as  we 
have  seen,  to  those  of  America. 

A  distinctive  character,  therefore,  is  given  to  the  fauna  of  this  period, 
by  which  we  seem  to  be  carried  one  step  farther  back  into  the  history  of 
organic  life. 

Supposed  Period  of  Invertebrate  Animals. 

We  have  seen  that  in  the  upper  part  of  the  Silurian  system  a  bone-bed 
occurs  near  Ludlow,  in  which  the  remains  of  fish  are  abundant,  and 
amongst  them  some  of  a  highly  organized  structure,  referred  to  the  genus 
Onchus.  We  are  indebted  to  Sir  R.  Murchison  for  having  first  an- 
nounced, in  1840,  the  discovery  of  these  ichthyolites,  and  he  then  spoke 
of  them  as  "  the  most  ancient  beings  of  their  class."  In  his  new  and 
excellent  work,  entitled  "  Siluria"  (p.  239),  he  reverts  to  the  opinion 
formerly  expressed  by  him,  and  observes  that  the  active  researches  of  the 
last  fourteen  years  in  Europe  and  America  "  have  failed  to  modify  that 


454  UPPER   SILURIAN   BONE-BED.  [Cn.  XXVII. 

generalization,"  adding,  "  the  Silurian  system,  therefore,  may  be  regarded 
as  representing  a  long  early  period,  in  which  no  vertebrated  animals  had 
been  called  into  existence." 

It  is  certainly  a  fact  well  worthy  of  our  attention,  that  as  yet  no  re- 
mains of  fish  are  on  record  as  coming  from  any  stratum  older  than  the 
base  of  the  "  Upper  Ludlow."  (See  above,  p.  432.)  When  we  reflect  on 
the  number  of  Mollusks,  Echinoderrns,  Corals,  Trilobites,  and  other  fossils 
already  obtained  from  Silurian  strata  below  "  the  Ludlow,"  we  may  well 
ask,  whether  any  other  set  of  fossiliferous  formations  were  ever  studied 
with  equal  diligence  and  over  so  vast  an  area  without  yielding  some 
ichthyolites. 

Nevertheless,  we  must  be  permitted  to  hesitate  before  we  accept,  even 
on  such  evidence,  so  sweeping  a  conclusion,  as  that  the  globe,  for  ages 
after  it  was  habitable  by  all  the  great  classes  of  invertebrate,  "emained 
wholly  untenanted  by  vertebrate  animals.  In  the  first  place,  we  must 
remember  that  we  have  detected  no  insects,  or  land-shells,  or  freshwater 
pulmoniferous  mollusks,  or  terrestrial  crustaceans,  or  plants  (except  fu- 
coids),  in  rocks  below  the  Upper  Silurian.  Their  absence  may  admit  of 
explanation,  by  supposing  all  the(deposits  of  that  era  hitherto  examined  to 
have  been  formed  in  seas  far  from  land  or  beyond  the  influence  of  rivers. 
Here  and  there  indeed  a  shallow- water,  or  even  a  littoral  deposit  may 
have  been  met  with,  as  in  North  Wales,  for  example,  and  North  America ; 
but,  speaking  generally,  the  Silurian  deposits,  as  at  present  known,  have 
certainly  a  more  pelagic  character  than  any  other  equally  important  for- 
mations. 

It  is  a  curious  fact,  and  not  perhaps  a  mere  fortuitous  coincidence,  that 
the  only  stratum  which  has  yielded  the  remains  of  land-plants  is  also  the 
only  one  which  has  afforded  the  bones  of  fish.  Bone-beds  in  general, 
such  as  that  of  the  Lias  near  Bristol,  those  of  the  Trias  near  Stuttgardt,  of 
the  Carboniferous  Limestone  near  Bristol  and  Armagh,  and  lastly  that  of 
the  "  Upper  Ludlow,"  are  remarkable  for  containing  teeth  and  bones, 
much,  rolled  and  implying  transportation  from  a  distance.  The  associa- 
tion of  the  spores  of  Lycopodiacese  (see  p.  432)  with  the  Ludlow  fish- 
bones shows  that  plants  had  been  washed  from  some  dry  land,  then 
existing,  and  had  been  drifted  into  a  common  submarine  receptacle 
with  the  bones.  More  usually,  however,  the  "  Upper  Ludlow,"  like 
the  "  Lower  Silurian,"  is  devoid  of  plants  and  equally  destitute  of  ich- 
thyolites. 

It  has  been  suggested  that  Cephalopoda  were  so  abundant  in  the  Si- 
lurian period  that  they  may  have  discharged  the  functions  of  fish ;  to 
which  we  may  reply  that  both  classes  coexisted  in  the  Upper  Silurian 
period,  and  both  of  them  swarmed  together  in  the  Carboniferous  and 
Liassic  Seas,  as  they  do  now  in  certain  parts  of  the  ocean.  We  may  also 
suggest  that  we  are  too  imperfectly  acquainted  with  the  distribution  of 
scattered  bones  and  teeth,  or  the  skeletons  of  dead  fish  on  the  floor  of  the 
existing  ocean,  to  have  a  right  to  theorize  with  confidence  on  the  absence 
of  such  relics  over  wide  spaces  at  former  eras. 


CH.  XXVIL]     ABSENCE   OF  FISH  IX  LOWER   SILURIAN.  455 

They  who  in  our  own  times  have  explored  the  bed  of  the  sea  inform 
us  that  it  is  in  general  as  barren  of  vertebrate  remains  as  the  soil  of  ? 
forest  on  which  thousands  of  mammalia  and  reptiles  may  have  flourished 
for  centuries.  In  the  summer  of  1850,  Professor  E.  Forbes  and  Mr. 
McAndrew  dredged  the  bed  of  the  British  seas  from  the  Isle  of  Portland 
to  the  Land's  End  in  Cornwall,  and  thence  again  to  Shetland,  recording 
and  tabulating  the  numbers  of  the  various  organic  bodies  brought  up  by 
them  in  the  course  of  140  distinct  dredgings,  made  at  different  distances 
from  the  shore,  some  a  quarter  of  a  mile,  others  forty  miles  distant.  The 
list  of  species  of  marine  invertebrate  animals,  whether  Radiata,  Mollusca, 
or  Articulata,  was  very  great,  and  the  number  of  individuals  enormous  ; 
but  the  only  instances  of  vertebrate  animals  consisted  of  a  few  ear-bones 
and  two  or  three  vertebrae  of  fish,  in  all  not  above  six  relics. 

It  is  still  more  extraordinary  that  Mr.  McAndrew  should  have  dredged 
the  great  "  Ling  Banks"  or  cod-fishery  grov-nds  off  the  Shetland 
Islands  for  shells  without  obtaining  the  bones  <r  teeth  of  any  dead 
fish,  although  he  sometimes  drew  up  live  fish  from  the  mud.  This 
is  the  more  singular,  because  there  are  some  areas  where  recent  fish- 
bones occur  in  the  same  northern  seas  in  profusion,  as  I  have  shown 
in  the  "  Principles  of  Geology"  (see  Index,  "  Vidal")  ;  two  bone-beds 
having  been  discovered  by  British  hydrographers,  one  in  the  Irish  sea, 
and  the  other  in  the  sea  near  the  Faroe  Isles,  the  first  of  them  two,  and 
the  other  three  and  a  half  miles  in  length,  where  the  lead  brings  up 
everywhere  the  vertebrae  of  fish  from  various  depths  between  45  to 
235  fathoms.  These  may  be  compared  to  the  Upper  Ludlow  bone- 
bed  ;  and  on  the  floor  of  the  ocean  of  our  times,  as  on  that  of  the 
Silurian  epoch,  there  are  other  wide  spaces  where  no  bones  are  imbedded 
in  mud  or  sand. 

It  may  be  true,  though  it  sounds  somewhat  like  a  paradox,  that  fish 
leave  behind  them  no  memorials  of  their  presence  in  places  where  they 
swarm  and  multiply  freely ;  whereas  currents  may  drift  their  bones  in 
great  numbers  to  regions  wholly  destitute  of  living  fish.  Such  a  state  of 
things  would  be  quite  analogous  to  what  takes  place  on  the  habitable 
land,  where,  instead  of  the  surface  becoming  encumbered  with  heaps 
of  skeletons  of  quadrupeds,  birds,  and  land-reptiles,  all  solid  bony  sub- 
stances are  removed  after  death  by  chemical  processes,  or  by  the 
digestive  powers  of  predaceous  beasts ;  so  that,  if  at  some  future  period 
a  geologist  should  seek  for  monuments  of  the  former  existence  ot 
such  creatures,  he  must  look  anywhere  rather  than  in  the  area  where 
they  flourished.  He  must  search  for  them  in  spots  which  were  cov- 
ered at  the  time  with  water,  and  to  which  somes  bones  or  carcases 
may  have  been  occasionally  carried  by  floods  and  permanently  buried  in 
sediment. 

In  the  annexed  Table,  a  few  dates  are  set  before  the  reader  of  the 
discovery  of  different  classes  of  animals  in  ancient  rocks,  to  enable  him 
to  perceive  at  a  glance  how  gradual  has  been  our  progress  in  tracing 
back  the  signs  of  Vertebrata  to  formations  of  high  antiquity.  Such  facts 


456 


PROGEESSIVE  DISCOVERY  OF  VERTEBRATA     [Cn.  XXVII 


may  be  useful  in  warning  us  not  to  assume  too  hastily  that  the  point 
which  our  retrospect  may  have  reached  at  the  present  moment  can  be 
regarded  as  fixing  the  date  of  the  first  introduction  of  any  one  class  of 
beings  upon  the  earth. 


Dates  of  the  Discovery  of  different  Classes  of  Fossil  Vertebrata  ;  show- 
ing the  gradual  Progress  made  in  tracing  them  to  Rocks  of  higher 
Antiquity. 


Year. 
f  1798. 

Mammalia,  -I  ,g,g 
[  184-7.' 
(  1782. 

Aves. 

(  1839. 

51710. 
1844. 
1852. 
1709. 
1793. 


Pisces. 


1828. 
1840. 


Formations. 
Middle  Eocene  (or  B.  i.  p.  222). 

Lower  Oolite. 
Upper  Trias. 

Middle  Eocene  (orB.  i.  p.  222). 

Lower  Eocene. 
Permian  (or  Zechstein). 
Carboniferous. 
Upper  Devonian. 

Permian  (or  Ivupfer-schiefer). 
Carboniferous  (Mountain  Lime- 
stone). 
Devonian. 
Upper  Silurian. 


Geographical  Localities. 
Paris  (Gypsum  of  Mont- 

martre).1 
Stonesfield.2 
Stuttgardt.3 
Paris  (Gypsum  ..    Mont- 

martre).4 
London  (Sheppey  Clay).6 

Thuringia.6 

Saarbruck,  near  Treves.7 

Elgin.8 

Thuringia.9 

Glasgow.10 

Caithness." 
Ludlow." 


I  Cuvier  (George).     Bulletin  Soc.  Philom.  xx.     Scattered  bones  were  found  in 
the  gypsum  some  years  before ;  but  they  were  determined  osteologically,  and 
their  true  geological  position  was  assigned  to  them  in  this  memoir. 

3  In  1818,  Cuvier,  visiting  the  Museum  of  Oxford,  decided  on  the  mammalian 
character  of  a  jaw  from  Stonesfield.  See  also  above,  p.  311. 

3  Plieninger,  Prof.     See  above,  p.  340. 

4  M.  Darcet  discovered,  and  Lamanon  figured,  as  a  fossil  bird,  some  remains 
from  Montmartre,  afterwards  recognized  as  such  by  Cuvier  (Ossemens  Foss.,  Art. 
"  Oiseaux"). 

8  Owen,  Prof.,  Geol.  Trans.  2d  Ser.  vol.  vi.  p.  203,  1839.  The  fossil  bird  dis- 
covered in  the  same  year  in  the  slates  of  Glaris  in  the  Alps,  and  at  first  referred 
to  the  chalk,  is  now  supposed  to  belong  to  the  Nummulitic  beds,  and  may  there- 
fore be  of  newer  date  than  the  Sheppey  Clay. 

6  The  fossil  monitor  of  Thuringia  (P rotor osaurus  Speneri,  V.  Meyer)  was  figured 
by  Spener,  of  Berlin,  in  1810.    (Miscel.  Berlin.) 

7  See  above,  p.  397. 

8  See  above,  p.  412.  _ 

8  Memorabilia  Saxonise  Subterr.,  Leipsic,  1709. 

10  History  of  Rutherglen,  by  Rev.  David  Ure,  1793. 

II  Sedgwick  and  Murchison,  Geol.  Trans.  2d  Ser.  vol.  iii.  p.  141,  1828. 
12  Sir  R.  Murchison.     See  above,  p.  431. 

06s.  The  evidence  derived  from  footprints,  though  often  to  be  relied  on,  is 
omitted  in  the  above  table,  as  being  less  exact  than  that  founded  on  bones  and 
teeth. 

How  many  living  writers  are  there  who,  before  the  year  1844,  gener- 
alized fearlessly  on  the  non-existence  of  reptiles  before  the  Permian  era  ! 
Yet,  in  the  course  of  ten  years,  they  have  lived  to  see  the  earliest  known 
date  of  the  creation  of  reptiles  carried  back  successively,  first  to  the  Car- 
boniferous, and  then  to  the  Upper  Devonian  periods.  Before  the  year 
1818,  it  was  the  popular  belief  that  the  Palseotherium  of  the  Paris  gyp- 
sum and  its  associates  were  the  first  warm-blooded  quadrupeds  that  ever 


CE.  XXVIL]  IN  OLDER  ROCKS.  457 

trod  the  surface  of  this  planet.  So  fixed  was  this  idea  in  the  minds  of  the 
majority  of  naturalists,  that,  when  at  length  the  Stonesfield  Mammalia 
awoke  from  a  slumber  of  three  or  four  great  periods,  the  apparition  failed 
to  make  them  renounce  their  creed. 

"  Unwilling  I  my  lips  unclose — 
Leave,  oh,  leave  me  to  repose." 

First,  the  antiquity  of  the  rock  was  called  in  question  ;  and  then  the  mam- 
malian character  of  the  relics.  Even  long  after  all  controversy  was  set  at 
rect  on  these  points,  the  real  import  of  the  new  revelation,  as  bearing  on 
the  doctrine  of  progressive  development,  was  far  from  being  duly  appre- 
ciated. 

It  is  clear  that  the  first  two  or  three  species,  encountered  in  any  country 
or  in  the  rocks  of  any  epoch,  cannot  be  taken  as  a  type  or  standard  for 
measuring  the  grade  of  organization  of  any  terrestrial  fauna,  ancient  or 
modern.  Suppose  that  the  two  or  three  oolitic  species  first  brought  to 
light  had  really  been  all  marsupial,  as  was  for  a  time  erroneously  im- 
agined, this  would  not  have  borne  out  the  inference  which  some  attempted 
to  deduce  from  it,  namely,  that  the  time  had  not  yet  come  for  the  crea- 
tion of  the  placental  tribes.  Or,  if  when  some  monodelph  were  at  last 
actually  recognized  (at  Stonesfield),  they  happened  to  be  of  diminutive 
size,  and  to  belong  to  the  insectivora,  we  are  not  entitled  to  deduce  from 
such  data  that  the  oolitic  fauna  ranked  low  in  the  general  scale,  as  the 
insectivora  may  do  in  an  existing  fauna.  The  real  significance  of  the  dis- 
coveries alluded  to  arises  from  the  aid  they  afford  us  in  estimating  the  true 
value  of  negative  evidence,  when  brought  to  bear  on  certain  speculative 
questions.  Every  zoologist  will  admit  that  between  the  first  creation  and 
the  final  extinction  of  any  one  of  the  five*  oolitic  mammalia  now  known 
there  were  many  successive  generations ;  and,  if  the  geographical  range 
of  each  species  was  limited  (which  we  have  no  right  to  assume),  still 
there  must  have  been  several  hundred  individuals  in  each  generation, 
and  probably,  when  the  species  reached  its  maximum,  several  thousands. 
When,  therefore,  we  encounter  for  the  first  time  in  1854  two  or  three 
jaws  of  a  Spalacotherium  in  the  Purbeck  limestone,  after  countless  speci- 
mens of  Mollusca  and  Crustacea,  and  hundreds  of  insects,  fish,  and  rep- 
tiles had  been  previously  collected  from  the  same  beds,  we  are  not  simply 
taught  that  these  individual  quadrupeds  flourished  at  the  era  in  question, 
but  that  thousands,  perhaps  hundreds  of  thousands,  of  the  same  species 
peopled  the  land  without  leaving  behind  them  any  trace  of  their  exist- 
ence, whether  in  the  shape  of  fossil  bones  or  footprints  ;  or,  if  they  left 
any  traces,  these  have  eluded  a  long  and  most  persevering  search. 

Moreover,  we  must  never  forget  how  many  of  the  dates  given  in  the 

*  I  had  written  four,  but  while  this  sheet  was  passing  through  the  press 
(Sept.  26,  1854)  the  discovery  of  another  species  of  insectivorous  mammal  from 
Stonesfield  was  announced  to  the  British  Association  at  Liverpool  by  Mr.  Charles- 
worth,  who  has  given  to  it  the  name  of  Stereognathus  ooliticus.  It  is  more  than 
twice  the  size  of  any  of  the  species  previously  obtained  from  the  same  formation, 
"We  have  now,  therefore,  including  the  recently  found  Spalacotherium  of  Pur- 
beck  (see  p.  295),  five  British  mammalia  from  the  oolite. 


458  VERTEBRATA  IN  THE  [Cn.  XXVII, 

above  table  (p.  456),  are  due  to  British  skill  and  energy,  Great  Britain 
being  still  the  only  country  in  which  mammalia  have  been  found  in 
Oolitic  rocks ;  the  only  region  where  any  reptiles  have  been  detected  in 
strata  as  old  as  the  Devonian  ;  the  only  one  wherein  the  bones  of  birds 
have  been  traced  back  as  far  as  the  London  Clay.  And,  if  geology  had 
been  cultivated  with  less  zeal  in  our  island,  we  should  know  nothing  as 
yet  of  two  extensive  assemblages  of  tertiary  mammalia  of  higher  antiquity 
than  the  fauna  of  the  Paris  gypsum  (already  cited  as  having  once  laid 
claim  to  be  the  earliest  that  ever  flourished  on  the  earth) — namely,  first, 
that  of  the  Headon  series  (see  above,  p.  212) ;  and,  secondly,  one  long 
prior  to  it  in  date,  and  antecedent  to  the  London  Clay.*  This  last  has 
already  afforded  us  indications  of  Quadrumana,  Cheiroptera,  Pachyder- 
mata,  and  Marsupialia  (see  p.  217).  How  then  can  we  doubt,  if  every 
area  on  the  globe  were  to  be  studied  with  the  same  diligence, — if  all 
Europe,  Asia,  Africa,  America,  and  Australia  were  equally  well  known, 
that  every  date  assigned  by  us  in  the  above  Table  for  the  earliest  recorded 
appearance  of  fish,  reptiles,  birds,  and  mammals  would  have  to  be  altered  ? 
Nay,  if  one  other  area,  such  as  part  of  Spain,  of  the  size  of  England  and 
Scotland,  were  subjected  to  the  same  scrutiny  (and  we  are  still  very  im- 
perfectly acquainted  even  with  Great  Britain),  each  class  of  Vertebrata 
would  probably  recede  one  or  more  steps  farther  back  into  the  abyss  ot 
time :  fish  might  penetrate  into  the  Lower  Silurian, — reptiles  into  the 
Lower  Devonian, — mammalia  into  the  Lower  Trias, — birds  into  the 
Chalk  or  Oolite, — and,  if  we  turn  to  the  Invertebrata,  Trilobites  and 
Cephalopods  might  descend  into  the  Lower  Cambrian, — and  some  stray 
zoophyte,  like  the  Oldhamia,  into  rocks  now  styled  "  azoic." 

Yet,  after  these  and  many  more  analogous  revisions  of  the  Table,  it 
might  still  be  just  as  easy  as  now  to  found  a  theory  of  progressive  devel- 
opment on  the  new  set  of  positive  and  negative  facts  thus  established ; 
for  the  order  of  chronological  succession  in  the  different  classes  of  fossil 
animals  would  probably  continue  the  same  as  now  ; — in  other  words,  our 
success  in  tracing  back  the  remains  of  each  class  to  remote  eras  would  be 
greatest  in  fishes,  next  in  reptiles,  next  in  mammalia,  and  least  in  birds. 
That  we  should  meet  with  ichthyolites  more  universally  at  each  era,  and 
at  greater  depths  in  the  series,  than  any  other  class  of  fossil  vertebrata, 
would  follow  partly  from  our  having  as  paleontologists  to  do  chiefly  with 
strata  of  marine  origin,  and  partly,  because  bones  of  fish,  however  partial 
and  capricious  their  distribution  on  the  bed  of  the  sea,  are  nevertheless 
more  easily  met  with  than  those  of  reptiles  or  mammalia.  In  like  man- 
ner, the  extreme  rarity  of  birds  in  recent  and  Pliocene  strata,  even  in  those 
of  freshwater  origin,  might  lead  us  to  anticipate  that  their  remains  would 
be  obtained  with  the  greatest  difficulty  in  the  older  rocks,  as  the  Table 
proves  to  be  the  case, — even  in  tertiary  strata,  wherein  we  can  more 
readily  find  deposits  formed  in  lakes  and  estuaries. 

*  A  bird's  bone  is  recorded  as  having  been  lately  found  in  the  "Woolwich 
beds  (beneath  the  London  clay),  by  Mr.  Prestwich ;  Geol.  Quart.  Journ.  vol.  x. 
p.  157. 


CH.  XXVII.J  OLD    FOSSILIFEROUS   PERIODS.  459 

The  only  incongruity  between  the  geological  results,  and  those  which 
our  dredging  experiences  might  have  led  us  to  anticipate  a  priori,  con- 
sists in  the  frequency  of  fossil  reptiles,  and  the  comparative  scarcity  of 
mammalia.  It  would  appear  that  during  all  the  secondary  periods,  not 
even  excepting  the  newest  part  of  the  cretaceous,  there  was  a  greater 
development  of  reptile  life  than  is  now  witnessed  in  any  part  of  the  globe. 
The  preponderance  of  this  class  over  the  mammalia  depended  probably 
on  climatal  and  geographical  conditions,  for  we  can  scarcely  refer  it  to 
"  progressive  development,"  by  which  the  vertebrate  type  was  steadily 
improving,  or  becoming  more  perfect,  as  Time  rolled  on.  We  cannot 
shut  our  eyes  to  the  positive  proofs  now  obtained  of  the  creation  of  mam- 
malia before  the  excess  of  reptiles  had  ceased, — nay,  apparently  before  it 
had  even  reached  its  maximum. 

In  conclusion,  I  shall  simply  express  my  own  conviction  that  we  are 
still  on  the  mere  threshold  of  our  inquiries ;  and  that,  as  in  the  last  fifty 
years,  so  in  the  next  half  century,  we  shall  be  called  upon  repeatedly  to 
modify  our  first  opinions  respecting  the  range  in  time  of  the  various  classes 
of  fossil  Vertebrata.  It  would  therefore  be  premature  to  generalize  at 
present  on  the  non-existence,  or  even  on  the  scarcity  of  Vertebrata, 
whether  terrestrial  or  aquatic,  at  periods  of  high  antiquity,  such  as  the 
Silurian  and  Cambrian.* 

*  For  observations  on  the  rarity  of  air-breathers  in  the  coal,  see  above,  p.  401. 


4-60  TRAP  EOCKS.  rCH.XX.VUl 


CHAPTER  XXVIII. 

VOLCANIC    ROCKS. 

Trap  rocks — K"ame,  whence  derived — Their  igneous  origin  at  first  doubted — 
Their  general  appearance  and  character — Volcanic  cones  and  craters,  how 
formed — Mineral  composition  and  texture  of  volcanic  rocks — Varieties  of 
felspar — Hornblende  and  augite — Isomorphism — Rocks,  how  to  be  studied — 
Basalt,  trachyte,  greenstone,  porphyry  scoria,  amygdaloid,  lava,  tuff— Agglo- 
merate— Laterite — Alphabetical  list,  and  explanation  of  names  and  synonyms 
of  volcanic  rocks — Table  of  the  analyses  of  minerals  most  abundant  in  the 
volcanic  and  hypogene  rocks. 

THE  aqueous  or  fossiliferous  rocks  having  now  been  described,  we  have 
next  to  examine  those  which  may  be  called  volcanic,  in  the  most  extended 
sense  of  that  term.  Suppose  a  a,  in  the  annexed  diagram,  to  represent 


a.  Hypogene  formations,  stratified  and  unstratified. 
&.  Aqueous  formations.  c.  Volcanic  rocks. 

the  crystalline  formations,  such  as  the  granitic  and  metamorphic ;  I  b  the 
fossiliferous  strata ;  and  c  c  the  volcanic  rocks.  These  last  are  sometimes 
found,  as  was  explained  in  the  first  chapter,  breaking  through  a  and  £>, 
sometimes  overlying  both,  and  occasionally  alternating  with  the  strata  b  b. 
They  also  are  seen,  in  some  instances,  to  pass  insensibly  into  the  unstrati- 
fied division  of  a,  or  the  Plutonic  rocks. 

When  geologists  first  began  to  examine  attentively  the  structure  of  the 
northern  and  western  parts  of  Europe,  they  were  almost  entirely  ignorant 
of  the  phenomena  of  existing  volcanoes.  They  found  certain  rocks,  for  the 
most  part  without  stratification,  and  of  a  peculiar  mineral  composition, 
to  which  they  gave  different  names,  such  as  basalt,  greenstone,  porphyry, 
and  amygdaloid.  All  these,  which  were  recognized  as  belonging  to  one 
family,  were  called  "  trap "  by  Bergmann,  from  trappa,  Swedish  for  a 
flight  of  steps — a  name  since  adopted  very  generally  into  the  nomencla- 
ture of  the  science ;  for  it  was  observed  that  many  rocks  of  this  class 
occurred  in  great  tabular  masses  of  unequal  extent,  so  as  to  form  a  suc- 
cession of  terraces  or  steps  on  the  sides  of  hills.  This  configuration 
appears  to  be  derived  from  two  causes.  First,  the  abrupt  original  ter- 
minations of  sheets  of  melted  matter,  which  have  spread,  whether  on 
the  land  or  bottom  of  the  sea,  over  a  level  surface.  For  we  know, 
in  the  case  of  lava  flowing  from  a  volcano,  that  a  stream,  when  it  has 


CH.  XXYIII]  COXES  AXD   CRATERS.  461 

ceased  to  flow,  and  grown  solid,  very  commonly  ends  in  a  steep  slope, 
as  at  «,  fig.  620.  But,  secondly,  the  step-like  appearance  arises  more 
frequently  from,  the  mode  in  which  hori- 
zontal masses  of  igneous  rock,  such  as  b  c, 
intercalated  between  aqueous  strata,  or 
showers  of  volcanic  dust  and  ashes,  have, 
subsequently  to  their  origin,  been  exposed, 
at  different  heights,  by  denudation.  Such 
an  outline,  it  is  true,  is  not  peculiar  to 

trap  rocks  ;  great  beds  of  limestone,  and         step-like  appearance  of  trap, 
other  hard  kinds  of  stone,  often  presenting 

similar  terraces  and  precipices ;  but  these  are  usually  on  a  smaller  scale, 
or  less  numerous,  than  the  volcanic  steps,  or  form  less  decided  features  in 
the  landscape,  as  being  less  distinct  in  structure  and  composition  from  the 
associated  rocks. 

Although  the  characters  of  trap  rocks  are  greatly  diversified,  the  be- 
ginner will  easily  learn  to  distinguish  them  as  a  class  from  the  aqueous 
formations.  Sometimes  they  present  themselves,  as  already  stated,  in 
tabular  masses,  which  are  not  divided  by  horizontal  planes  of  stratification 
in  the  manner  of  sedimentary  deposits.  Sometimes  they  form  chains  of 
hills  often  conical  in  shape.  Not  unfrequently  they  are  seen  as  "  dikes  " 
or  wall-like  masses,  intersecting  fossiliferous  beds.  The  rock  is  occasion- 
ally columnar,  the  columns  sometimes  decomposing  into  balls  of  various 
sizes,  from  a  few  inches  to  several  feet  in  diameter.  The  decomposing 
surface  very  commonly  assumes  a  coating  of  a  rusty  iron  color,  from  the 
oxidation  of  ferruginous  matter,  so  abundant  in  the  traps  in  which  augite 
or  hornblende  occurs ;  or,  in  the  felspathic  varieties  of  trap,  it  acquires  a 
white  opake  coating,  from  the  bleaching  of  the  mineral  called  felspar. 
On  examining  any  of  these  volcanic  rocks,  where  they  have  not  suffered 
disintegration,  we  rarely  fail  to  detect  a  crystalline  arrangement  in  one  or 
more  of  the  component  minerals.  Sometimes  the  texture  of  the  mass  is 
cellular  or  porous,  or  we  perceive  that  it  has  once  been  full  of  pores  and 
cells,  which  have  afterwards  become  filled  with  carbonate  of  lime,  or 
other  infiltrated  mineral. 

Most  of  the  volcanic  rocks  produce  a  fertile  soil  by  their  disintegra- 
tion. It  seems  that  their  component  ingredients,  silica,  alumina,  lime, 
potash,  iron,  and  the  rest,  are  in  proportions  well  fitted  for  the  growth  of 
vegetation.  As  they  do  not  effervesce  with  acids,  a  deficiency  of  calca- 
reous matter  might  at  first  be  suspected  ;  but  although  the  carbonate  of 
lime  is  rare,  except  in  the  nodules  of  amygdaloids,  yet  it  will  be  seen  that 
lime  sometimes  enters  largely  into  the  composition  of  augite  and  horn- 
blende. (See  Table, .  p.  475.) 

Cones  and  Craters. — In  regions  where  the  eruption  of  volcanic  matter 
has  taken  place  in  the  open  air,  and  where  the  surface  has  never  since 
been  subjected  to  great  aqueous  denudation,  cones  and  craters  constitute 
the  most  striking  peculiarity  of  this  class  of  formations.  Many  hundreds 
of  these  cones  are  seen  in  central  France,  in  the  ancient  provinces  of 


462 


COMPOSITION  AND  NOMENCLATURE       [On.  XXVIII. 


Auvergne,  Velay,  and  Vivarais,  where  they  observe,  for  the  most  part,  a 
linear  arrangement,  and  form  chains  of  hills.  Although  none  of  the 
eruptions  have  happened  within  the  historical  era,  the  streams  of  lava 
may  still  be  traced  distinctly  descending  from  many  of  the  craters,  and 
following  the  lowest  levels  of  the  existing  valleys.  The  origin  of  the 


Fig.  621. 


Part  of  the  chain  of  extinct  volcanoes  called  the  Monts  Dome,  Auvergne.     (Scropc.) 

cone  and  ciater-shaped  hill  is  well  understood,  the  growth  of  many  having 
been  watched  during  volcanic  eruptions.  A  chasm  or  fissure  first  opens 
in  the  earth,  from  which  great  volumes  of  steam  and  other  gases  are 
evolved.  The  explosions  are  so  violent  as  to  hurl  up  into  the  air  fragments 
of  broken  stone,  parts  of  which  are  shivered  into  minute  atoms.  At  the 
same  time  melted  stone  or  lava  usually  ascends  through  the  chimney  or 
vent  by  which  the  gases  make  their  escape.  Although  extremely  heavy, 
this  lava  is  forced  up  by  the  expansive  power  of  entangled  gaseous  fluids, 
chiefly  steam  or  aqueous  vapor,  exactly  in  the  same  manner  as  water  is 
made  to  boil  over  the  edge  of  a  vessel  when  steam  has  been  generated  at 
.  the  bottom  by  heat.  Large  quantities  of  the  lava  are  also  shot  up  into 
the  air,  where  it  separates  into  fragments,  and  acquires  a  spongy  texture 
by  the  sudden  enlargement  of  the  included  gases,  and  thus  forms  sconce, 
other  portions  being  reduced  to  an  impalpable  powder  or  dust.  The 
showering  down  of  the  various  ejected  materials  round  the  orifice  of  erup- 
tion gives  rise  to  a  conical  mound,  in  which  the  successive  envelopes  of 
sand  and  scoriae  form  layers,  dipping  on  all  sides  from  a  central  axis.  In 
the  mean  time  a  hollow,  called  a  crater,  has  been  kept  open  in  the 
middle  of  the  mound  by  the  continued  passage  upwards  of  steam  and 
other  gaseous  fluids.  The  lava  sometimes  flows  over  the  edge  of  the 
crater,  and  thus  thickens  and  strengthens  the  sides  of  the  cone  ;  but  some- 
times it  breaks  down  the  cone  on  one  side  (see  fig.  621),  and  often  it  flows 
out  from  a  fissure  at  the  base  of  the  hill,  or  at  some  distance  from  its  base.* 
Composition  and  Nomenclature. — Before  speaking  of  the  connection 
between  the  products  of  modern  volcanoes  and  the  rocks  usually  styled 
trappean ;  and  before  describing  the  external  forms  of  both,  and  the 
manner  and  position  in  which  they  occur  in  the  earth's  crust,  it  will 
be  desirable  to  treat  of  their  mineral  composition  and  names.  The 
varieties  most  frequently  spoken  of  are  basalt  and  trachyte,  to  which 


*  For  a  description  and  theory  of  active  volcanoes,  see  Principles  of  Geology, 
chaps,  xxiv.  et  seq.  and  xxxii. 


OH.  XXVIIL]  OF   VOLCANIC   ROCKS.  463 

dolerite,  greenstone,  clinkstone,  and  others  might  be  added  ;  while  those 
founded  chiefly  on  peculiarities  of  texture,  are  porphyry,  amygdaloid,  lava, 
volcanic  breccia  or  agglomerate,  tuff,  scoriae,  and  pumice.  It  may  be 
stated  generally,  that  all  these  are  mainly  composed  of  two  minerals, 
or  families  of  simple  minerals,  felspar  and  hornblende  ;  but  the  felspar 
preponderates  greatly  even  in  those  rocks  to  which  the  hornblendic  min- 
eral imparts  its  distinctive  character  and  prevailing  color. 

The  two  minerals  alluded  to  may  be  regarded  as  two  groups,  rather 
than  species.  Felspar,  for  example,  may  be,  first,  common  felspar  (often 
called  Orthoclase),  that  is  to  say,  potash-felspar,  in  which  the  predominant 
alkali  is  potash  (see  Table,  p.  475) ;  or,  secondly,  albite,  that  is  to  say, 
soda-felspar,  where  the  predominant  alkali  is  soda  instead  of  potash  ;  or, 
thirdly,  Oligoclase ;  or,  fourthly,  Labrador-felspar  (Labradorite),  which 
differs  not  only  in  its  iridescent  hues,  but  also  in  its  angle  of  fracture  or 
cleavage,  and  its  composition.  We  also  read  much  of  two  other  kinds, 
called  glassy  felspar  and  compact  felspar,  which,  however,  cannot  rank  as 
varieties  of  equal  importance,  but  both  the  albitic  and  common  felspar 
appear  sometimes  in  transparent  or  glassy  crystals ;  and  as  to  compact 
felspar,  it  is  a  compound  of  a  less  definite  nature,  sometimes  containing 
largely  both  soda  and  potash ;  and  which  might  be  called  a  felspathic 
paste,  being  the  residuary  matter  after  portions  of  the  original  matrix 
have  crystallized.  The  more  recent  analyses  have  shown  that  all  the 
varieties  or  species  of  felspar  may  contain  both  potash  and  soda,  al- 
though in  some  of  them  the  one,  and  in  others  the  other  alkali  greatly 
prevails. 

The  hornblendic  group  consists  principally  of  two  varieties ;  first,  horn- 
blende, and,  secondly,  augite,  which  were  once  regarded  as  very  distinct, 
although  now  some  eminent  mineralogists  are  in  doubt  whether  they  are 
not  one  and  the  same  mineral,  differing  only  as  one  crystalline  form  of 
native  sulphur  differs  from  another. 

The  history  of  the  changes  of  opinion  on  this  point  is  curious  and  in- 
structive. Werner  first  distinguished  augite  from  hornblende ;  and  his 
proposal  to  separate  them  obtained  afterwards  the  sanction  of  Haiiy, 
Mohs,  and  other  celebrated  mineralogists.  It  was  agreed  that  the  form 
of  the  crystals  of  the  two  species  were  different,  and  their  structure,  as 
shown  by  cleavage,  that  is  to  say,  by  breaking  or  cleaving  the  mineral 
with  a  chisel,  or  a  blow  of  the  hammer,  in  the  direction  in  which  it 
yields  most  readily.  It  was  also  found  by  analysis  that  augite  usually 
contained  more  lime,  less  alumina,  and  no  fluoric  acid ;  which  last,  though 
not  always  found  in  hornblende,  often  enters  into  its  composition  in  mi- 
nute quantity.  In  addition  to  these  characters,  it  was  remarked  as  a 
geological  fact,  that  augite  and  hornblende  are  very  rarely  associated  to- 
gether in  the  same  rock  ;  and  that  when  this  happened,  as  in  some  lavas 
of  modern  date,  the  hornblende  occurs  in  the  mass  of  the  rock,  where 
crystallization  may  have  taken  place  more  slowly,  while  the  augite  merely 
lines  cavities  where  the  crystals  may  have  been  produced  rapidly.  It 
was  also  remarked,  that  in  the  crystalline  slags  of  furnaces,  augitic  forms 


464  THEORY  OF  ISOMORPHISM.  [On.  XXVIII 

were  frequent,  the  liornblendic  entirely  absent ;  hence  it  was  conjec- 
tured that  hornblende  might  be  the  result  of  slow,  and  augite  of  rapid 
cooling.  This  view  was  confirmed  by  the  fact,  that  Mitscherlich  and 
Berthier  were  able  to  make  augite  artificially,  but  could  never  succeed 
in  forming  hornblende.  Lastly,  Gustavus  Rose  fused  a  mass  of  horn- 
blende in  a  porcelain  furnace,  and  found  that  it  did  not,  on  cooling, 
assume  its  previous  shape,  but  invariably  took  that  of  augite.  The 
same  mineralogist  observed  certain  crystals  in  rocks  from  Siberia  which 
presented  a  hornblende  cleavage,  while  they  had  the  external  form  of 
augite. 

If,  from  these  data,  it  is  inferred  that  the  same  substance  may  assume 
the  crystalline  forms  of  hornblende  or  augite  indifferently,  according  to 
the  more  or  less  rapid  cooling  of  the  melted  mass,  it  is  nevertheless 
certain  that  the  variety  commonly  called  augite,  and  recognized  by  a 
peculiar  crystalline  form,  has  usually  more  lime  in  it,  and  less  alumina, 
than  that  called  hornblende,  although  the  quantities  of  these  elements 
do  not  seem  to  be  always  the  same.  Unquestionably  the  facts  and  ex- 
periments above  mentioned  show  the  very  near  affinity  of  hornblende 
and  augite  ;  but  even  the  convertibility  of  one  into  the  other,  by  melting 
and  recrystallizing,  does  not  perhaps  demonstrate  their  absolute  identity. 
For  there  is  often  some  portion  of  the  materials  in  a  crystal  which  are 
not  in  perfect  chemical  combination  with  the  rest.  Carbonate  of  lime, 
for  example,  sometimes  carries  with  it  a  considerable  quantity  of  silex 
into  its  own  form  of  crystal,  the  silex  being  mechanically  mixed  as 
sand,  and  yet  not  preventing  the  carbonate  of  lime  from  assuming  the 
form  proper  to  it.  This  is  an  extreme  case,  but  in  many  others  some 
one  or  more  of  the  ingredients  in  a  crystal  may  be  excluded  from 
perfect  chemical  union ;  and  after  fusion,  when  the  mass  recrystallizes, 
the  same  elements  may  combine  perfectly  or  in  new  proportions,  and 
thus  a  new  mineral  may  be  produced.  Or  some  one  of  the  gaseous 
elements  of  the  atmosphere,  the  oxygen,  for  example,  may,  when  the 
melted  matter  reconsolidates,  combine  with  some  one  of  the  component 
elements. 

The  different  quantity  of  the  impurities  or  refuse  above  alluded  to, 
which  may  occur  in  all  but  the  most  transparent  and  perfect  crystals, 
may  partly  explain  the  discordant  results  at  which  experienced  chemists 
have  arrived  in  their  analysis  of  the  same  mineral.  For  the  reader  will 
find  that  crystals  of  a  mineral  determined  to  be  the  same  by  physical 
characters,  crystalline  form,  and  optical  properties,  have  often  been  de- 
clared by  skilful  analyzers  to  be  composed  of  distinct  elements.  (See 
the  table  at  p.  475.)  This  disagreement  seemed  at  first  subversive  of 
the  atomic  theory,  or  the  doctrine  that  there  is  a  fixed  and  constant  re- 
lation between  the  crystalline  form  and  structure  of  a  mineral  and  its 
chemical  composition.  The  apparent  anomaly,  however,  which  threat- 
ened to  throw  the  whole  science  of  mineralogy  into  confusion,  was  in  a 
great  degree  reconciled  to  fixed  principles  by  the  discoveries  of  Professor 
Mitscherlich  at  Berlin,  who  ascertained  that  the  composition  of  the  min- 


Ca  XXVIIL]  PYEOXEXE — AMPHIBOLE.  465 

erals  which  had  appeared  so  variable,  was  governed  by  a  general  law,  to 
which  he  gave  the  name  of  isomorphism  (from  itfo^,  isos,  equal,  and  M-op<p^, 
morphe,  form).  According  to  this  law,  the  ingredients  of  a  given  species 
of  mineral  are  not  absolutely  fixed  as  to  their  kind  and  quality ;  but  one 
ingredient  may  be  replaced  by  an  equivalent  portion  of  some  analogous 
ingredient  Thus,  in  augite,  the  lime  may  be  in  part  replaced  by  por- 
tions of  protoxide  of  iron,  or  of  manganese,  while  the  form  of  the  crystal, 
and  the  angle  of  its  cleavage  planes,  remain  the  same.  These  vicarious 
substitutions,  however,  of  particular  elements  cannot  exceed  certain  de- 
fined limits. 

Pyroxene,  a  name  of  Haiiy's,  is  often  used  for  augite  in  descriptions  of 
volcanic  rocks.  It  is  properly,  according  to  M.  Delesse,  a  general  name, 
under  which  Augite,  Diallage,  and  Hypersthene  may  be  united,  for  these 
three  are  varieties  of  one  and  the  same  mineral  species,  having  the  same 
chemical  formula  with  variable  bases. 

Amphibole  is  in  like  manner  a  general  term  under  which  Hornblende 
and  Actinolite  may  be  united. 

Having  been  led  into  this  digression  on  some  recent  steps  made  in  the 
progress  of  mineralogy,  I  may  here  observe  that  the  geological  student 
must  endeavor  as  soon  as  possible  to  familiarize  himself  with  the  char- 
acters of  five  at  least  of  the  most  abundant  simple  minerals  of  which 
rocks  are  composed.  These  are  felspar,  quartz,  mica,  hornblende,  and 
carbonate  of  lime.  This  knowledge  cannot  be  acquired  from  books,  but 
requires  personal  inspection,  and  the  aid  of  a  teacher.  It  is  well  to  ac- 
ctistom  the  eye  to  know  the  appearance  of  rocks  under  the  lens.  To 
learn  to  distinguish  felspar  from  quartz  is  the  most  important  step  to  be 
first  aimed  at.  In  general  we  may  know  the  felspar  because  it  can  be 
scratched  with  the  point  of  a  knife,  whereas  the  quartz,  fi-om  its  extreme 
hardness,  receives  no  impression.  But  when  these  two  minerals  occur  in 
a  granular  and  uncrystallized  state,  the  young  geologist  must  not  be 
discouraged  if,  after  considerable  practice,  he  often  fails  to  distinguish 
them  by  the  eye  alone.  If  the  felspar  is  in  crystals,  it  is  easily  recog- 
nized by  its  cleavage ;  but  when  in  grains  the  blow-pipe  must  be  used, 
for  the  edges  of  the  grains  can  be  rounded  in  the  flame,  whereas  those  of 
quartz  are  infusible.  If  the  geologist  is  desirous  of  detecting  the  varieties 
of  felspar  above  enumerated,  or  distinguishing  hornblende  from  augite,  it 
will  often  be  necessary  to  use  the  reflecting  goniometer  as  a  test  of  the 
angle  of  cleavage,  and  shape  of  the  crystal.  The  use  of  this  instrument 
will  not  be  found  difficult. 

The  external  characters  and  composition  of  the  felspars  are  extremely 
different  from  those  of  augite  or  hornblende  ;  so  that  the  volcanic  rocks 
in  which  either  of  these  minerals  play  a  conspicuous  part  are  easily  re- 
cognizable. But  there  are  mixtures  of  the  two  elements  in  very  different 
proportions,  the  mass  being  sometimes  exclusively  composed  of  felspar, 
and  at  other  times  largely  of  augite.  Between  the  two  extremes  there  is 
almost  every  intermediate  gradation ;  yet  certain  compounds  prevail  so 
extensively  in  nature,  and  preserve  so  much  uniformity  of  aspect  and 

30 


466  BASALT — AUGITE — TEACHYTE.  [Ca  XXVIII 

composition,  that  it  is  useful  in  geology  to  regard  them  as  distinct  rocks, 
and  to  assign  names  to  them,  such  as  basalt,  greenstone,  trachyte,  and 
others  presently  to  be  mentioned. 

Basalt. — As  an  example  of  rocks  in  which  augite  is  a  conspicuous 
ingredient,  basalt  may  first  be  mentioned.  Although  we  are  more  fa- 
miliar with  this  term  than  with  that  of  any  other  kind  of  trap,  it  is  dif- 
ficult to  define  it,  the  name  having  been  used  so  comprehensively,  and 
sometimes  so  vaguely.  It  has  been  generally  applied  to  any  trap  rock 
of  a  black,  bluish,  or  leaden-gray  color,  having  a  uniform  and  compact 
texture.  Most  strictly,  it  consists  of  an  intimate  mixture  of  felspar,  augite, 
and  iron,  to  which  a  mineral  of  an  olive-green  color,  called  olivine,  is 
often  superadded,  in  distinct  grains  or  nodular  masses.  The  iron  is 
usually  magnetic,  and  is  often  accompanied  by  another  metal,  titanium. 
The  term  "  Dolerite"  is  now  much  used  for  this  rock,  when  the  felspar  is 
of  the  variety  called  Labradorite,  as  in  the  lavas  of  Etna.  Basalt,  ac- 
cording to  Dr.  Daubeny,  in  its  more  strict  sense,  is  composed  of  "  an  in- 
timate mixture  of  augite  with  a  zeolitic  mineral  which  appears  to  have 
been  formed  out  of  Labradorite  by  the  addition  of  water,  the  presence  of 
water  being  in  all  zeolites  the  cause  of  that  bubbling  up  under  the  blow- 
pipe, to  which  they  owe  their  appellation."*  Of  late  years  the  analyses  of 
M.  Delesse  and  other  eminent  mineralogists  have  shown  that  the  opinion 
once  entertained,  that  augite  was  the  prevailing  mineral  in  basalt,  or 
even  in  the  most  augitic  trap  rocks,  must  be  abandoned.  Although 
its  presence  gives  to  these  rocks  their  distinctive  character  as  con- 
trasted with  trachytes,  still  the  principal  element  in  their  composition  is 
felspar. 

Augite  rock  has,  indeed,  been  defined  by  Leonhard  as  being  made  up 
principally  or  wholly  of  augite,f  and  in  some  veinstones,  says  Delesse, 
such  a  rock  may  be  found  ;  but  the  greater  part  of  what  passes  by  the 
name  of  augite  rock  is  more  rich  in  green  felspar  than  in  augite.  Am- 
phibolite,  in  like  manner,  or  Hornblende  rock,  is  a  trap  of  the  basaltic 
family,  in  which  there  is  much  hornblende,  and  in  which  this  mineral 
has  been  supposed  to  predominate  ;  but  Delesse  finds,  by  analysis,  that 
the  felspar  may  be  in  excess,  the  base  being  felspathic. 

In  some  varieties  of  basalt  the  quantity  of  olivine  is  very  great ; 
and  as  this  mineral  differs  but  slightly  in  its  chemical  composition 
from  serpentine  (see  Table  of  Analysis,  p.  475),  containing  even  a 
larger  proportion  of  magnesia  than  serpentine,  it  has  been  suggested 
with  much  probability  that  in  the  course  of  ages  some  basalts  highly 
charged  with  olivine  may  be  turned,  by  metamorphic  action,  into  ser- 
pentine. 

Trachyte. — This  name,  derived  from  rpa^u^,  rough,  has  been  given  to 
the  felspathic  class  of  volcanic  rocks  which  have  a  coarse,  cellular  paste, 
rough  and  gritty  to  the  touch.  This  paste  has  commonly  been  supposed 
to  consist  chiefly  of  albite,  but  according  to  M.  Delesse  it  is  variable  in 

*  Volcanoes,  2d  ed.  p.  18.  \  Mineralreich,  2d  ed.  p.  85. 


CH.  XXVIIL]      TRACHYTE   PORPHYRY — CLINKSTONE.  467 

composition,  its  prevailing  alkali  being  soda.  Through  the  base  are 
disseminated  crystals  of  glassy  felspar,  mica,  and  sometimes  quartz  and 
hornblende,  although  in  the  trachyte,  properly  so  called,  there  is  no 
quartz.  The  varieties  of  felspar  which  occur  in  trachyte  are  trisilicates, 
or  those  in  which  the  silica  is  to  the  alumina  in  the  proportion  of  three 
atoms  to  one.* 

Trachytic  Porphyry,  according  to  Abich,  has  the  ordinary  composi- 
tion of  trachyte,  with  quartz  superadded,  and  without  any  augite  or  tita- 
niferous  iron.  Andesite  is  a  name  given  by  Gustavus  Rose  to  a  trachyte 
of  the  Andes,  which  contains  the  felspar  called  Andesin,  together  with 
glassy  felspar  (orthoclase)  and  hornblende  disseminated  through  a  dark- 
colored  base. 

Clinkstone,  or  Phonolite. — Among  the  felspathic  products  of  volcanic 
action,  this  rock  is  remarkable  for  its  tendency  to  lamination,  which  is 
sometimes  such  that  it  affords  tiles  for  roofing.  It  rings  when  struck 
with  the  hammer,  whence  its  name  ;  is  compact,  and  usually  of  a  gray- 
ish blue  or  brownish  color  ;  is  variable  in  composition,  but  almost  entirely 
composed  of  felspar,  and  in  some  cases,  according  to  Gmelin,  of  felspar 
and  mesotype.  When  it  contains  disseminated  crystals  of  felspar,  it  is 
called  Clinkstone  porphyry. 

Greenstone  is  the  most  abundant  of  those  volcanic  rocks  which  are 
intermediate  in  their  composition  between  the  Basalts  and  Trachytes. 
The  name  has  usually  been  extended  to  all  granular  mixtures,  whether  of 
hornblende  and  felspar,  or  of  augite  and  felspar.  The  term  diorite  has 
been  applied  exclusively  to  compounds  of  hornblende  and  felspar.  Ac- 
cording to  the  analyses  of  Delesse  and  others,  the  chief  cause  of  the  green 
color,  in  most  greenstones,  is  not  green  hornblende  nor  augite,  but  a  green 
siliceous  base,  very  variable  and  indefinite  in  its  composition.  The  dark 
color,  however,  of  diorite  is  usually  derived  from  disseminated  plates  of 
hornblende. 

The  Basalts  contain  a  smaller  quantity  of  silica  than  the  Trachytes,  and 
a  larger  proportion  of  lime  and  magnesia.  Hence,  independently  of  the 
frequent  presence  of  iron,  basalt  is  heavier.  Abich  has  therefore  pro- 
posed that  we  should  weigh  these  rocks,  in  order  to  appreciate  their  com- 
position in  cases  where  it  is  impossible  to  separate  their  component  min- 
erals. Thus,  the  variety  of  basalt  called  dolerite,  which  contains  53  per 
cent,  of  silica,  has  a  specific  gravity  of  2-86  ;  whereas  trachyte,  which  has 
66  per  cent,  of  silica,  has  a  sp.  gr.  of  only  2-68  ;  trachytic  porphyry,  con- 
taining 69  per  cent,  of  silica,  a  sp.  gr.  of  only  2-58.  If  we  then  take 
a  rock  of  intermediate  composition,  such  as  that  prevailing  in  the 
Peak  of  Teneriffe,  which  Abich  calls  Trachyte-dolerite,  its  proportion  of 
silica  being  intermediate,  or  58  per  cent.,  it  weighs  2'78,  or  more  than 
trachyte,  and  less  than  basalt.f  The  basalts  are  generally  dark  in  color, 
sometimes  almost  black,  whereas  the  trachytes  are  gray,  and  even  occa- 
sionally white.  As  compared  with  the  granitic  rocks,  basalts  and  tra- 
chytes contain  both  of  them  more  soda  in  their  composition,  the  potash- 
*  Dr.  Daubeny  on  Volcanoes,  2d  ed.  pp.  14,  15.  f  Ibid. 


468  FOKFHYRY — AMYGDALOID.  [Cs.  XXYIIL 

felspars  being  generally  abundant  in  the  granites.  The  volcanic  rocks 
moreover,  whether  basaltic  or  trachytic,  contain  less  silica  than  the  gra- 
nites, in  which  last  the  excess  of  silica  has  gone  to  form  quartz.  This 
mineral,  so  conspicuous  in  granite,  is  usually  wanting  in  the  volcanic  for- 
mations, and  never  predominates  in  them. 

The  fusibility  of  the  igneous  rocks  generally  exceeds  that  of  other 
rocks,  for  the  alkaline  matter  and  lime  which  commonly  abound  in  their 
composition  serve  as  a  flux  to  the  large  quantity  of  silica,  which  would  be 
otherwise  so  refractory  an  ingredient. 

We  may  now  pass  to  the  consideration  of  those  igneous  rocks,  the 
characters  of  which  are  founded  on  their  form  rather  than  their  com- 
position. 

Porphyry  is  one  of  this  class,  and  very  characteristic  of  the  volcanic 
formations.     When  distinct  crystals  of  one  or  more  minerals  are  scattered 
through  an  earthy  or  compact  base,  the  rock  is  termed  a  porphyry  (see 
fig.  622).     Thus  trachyte  is  porphyritic  ;  for  in  it,  as  in  many  modern 
lavas,  there  are  crystals  of  felspar ;  but  in  some  porphyries  the  crystals 
are  of  augite,  olivine,  or  other  minerals.     If  the  base  be  greenstone, 
basalt,  or  pitchstone,  the  rock   may  be 
denominated  greenstone-porphyry,  pitch- 
stone  porphyry,  and  so  forth.     The  old 
classical  type  of  this  form  of  rock  is  the 
red  porphyry  of  Egypt,  or  the  well-known 
"  Rosso  antico."     It  consists,  according  to 
Delesse,  of  a  red  felspathic  base  in  which 
are  disseminated  rose-colored  crystals  of 
the  felspar  called  oligoclase,  with  some 
plates  of  blackish  hornblende  and  grains 
of  oxidized  iron-ore  (fer  oligiste).     Red 
quartziferous  porphyry  is  a  much  more 
siliceous  rock,  containing  about  70  or  80     mite  ^  in  a  dark  base 

per  Cent,  of  silex,  while  that  of  Egypt  has  of  hornblende  and  felspar. 

only  62  per  cent. 

Amygdaloid. — This  is  also  another  form  of  igneous  rock,  admitting  of 
every  variety  of  composition.  It  comprehends  any  rock  in  which  round 
or  almond-shaped  nodules  of  some  mineral,  such  as  agate,  chalcedony,  cal- 
careous spar,  or  zeolite,  are  scattered  through  a  base  of  wacke,  basalt, 
greenstone,  or  other  kind  of  trap.  It  derives  its  name  from  the  Greek 
word  amygdala,  an  almond.  The  origin  of  this  structure  cannot  be 
doubted,  for  we  may  trace  the  process  of  its  formation  in  modern  lavas. 
Small  pores  or  cells  are  caused  by  bubbles  of  steam  and  gas  confined  in 
the  melted  matter.  After  or  during  consolidation,  these  empty  spaces 
are  gradually  filled  up  by  matter  separating  from  the  mass,  or  infiltered 
by  water  permeating  the  rock.  As  these  bubbles  have  been  sometimes 
lengthened  by  the  flow  of  the  lava  before  it  finally  cooled,  the  contents  of 
such  cavities  have  the  form  of  almonds.  In  some  of  the  amygdaloidal 
traps  of  Scotland,  where  the  nodules  have  decomposed,  the  empty  cells 


CH.  XXVIIL] 


LAVA — SCORIJE — PUMICE. 


409 


Fig.68a 


Scoriaceous  lava  in  part  converted  into  an 

amygdaloid. 

Montagn  e  de  la  Veille,  Department  of  Pay 
de  Dome,  France. 


are  seen  to  have  a  glazed  or  vitreous  coating,  and  in  this  respect  exactly 
resemble  scoriaceous  lavas,  or  the  slags  of  furnaces. 

The  annexed  figure  represents  a 
fragment  of  stone  taken  from  the 
upper  part  of  a  sheet  of  basaltic  lava 
in  Auvergne.  One  half  is  scoria- 
ceous, the  pores  being  perfectly  emp- 
ty; the  other  part  is  amygdaloidal, 
the  pores  or  cells  being  mostly  filled 
up  with  carbonate  of  lime,  forming 
white  kernels. 

Lava. — This  term  has  a  some- 
what vague  signification,  having 
been  applied  to  all  melted  matter 
observed  to  flow  in  streams  from 
volcanic  vents.  When  this  matter 
consolidates  in  the  open  air,  the 
upper  part  is  usually  scoriaceous, 
and  the  mass  becomes  more  and 
more  stony  as  we  descend,  or  in  proportion  as  it  has  consolidated  more 
slowly  and  under  greater  pressure.  At  the  bottom,  however,  of  a  stream 
of  lava,  a  small  portion  of  scoriaceous  rock  very  frequently  occuss,  formed 
by  the  first  thin  sheet  of  liquid  matter,  which  often  precedes  the  main 
current,  or  in  consequence  of  the  contact  with  water  in  or  upon  the 
damp  soil. 

The  more  compact  lavas  are  often  porphyritic,  but  even  the  scoriaceous 
part  sometimes  contains  imperfect  crystals,  which  have  been  derived  from 
some  older  rocks,  in  which  the  crystals  pre-existed,  but  were  not  melted, 
as  being  more  infusible  in  their  nature. 

Although  melted  matter  rising  in  a  crater,  and  even  that  which 
enters  a  rent  on  the  side  of  a  crater,  is  called  lava,  yet  this  term 
belongs  more  properly  to  that  which  has  flowed  either  in  the  open 
air  or  on  the  .bed  of  a  lake  or  sea.  If  the  same  fluid  has  not  reached 
the  surface,  but  has  been  merely  injected  into  fissures  below  ground,  it 
is  called  trap. 

There  is  every  variety  of  composition  in  lavas ;  some  are  trachytic,  as 
in  the  Peak  of  Teneriffe  ;  a  great  number  are  basaltic,  as  in  Vesuvius  and 
Auvergne ;  others  are  Andesitie,  as  those  of  Chili ;  some  of  the  most 
modern  in  Vesuvius  consist  of  green  augite,  and  many  of  those  of  Etna  of 
augite  and  Labrador-felspar.* 

Scorice  and  Pumice  may  next  be  mentioned  as  porous  rocks,  pro- 
duced by  the  action  of  gases  on  materials  melted  by  volcanic  heat. 
Scorice  are  usually  of  a  reddish-brown  and  black  color,  and  are  the 
cinders  and  slags  of  basaltic  or  augitic  lavas.  Pumice  is  a  light,  spongy, 
fibrous  substance,  produced  by  the  action  of  gases  on  trachytic  and  other 

*  G.  Rose,  Ann.  des  Mines,  torn,  viii.  p.  32. 


470  VOLCANIC  TUFF — PALAGCXNTTE  TUFF.      [On.  XXVI1J. 

lavas ;  the  relation,  however,  of  its  origin  to  the  composition  of  lava  is  not 
yet  well  understood.  Von  Buch  says  that  it  never  occurs  where  only 
Labrador-felspar  is  present. 

Volcanic  tuff,  Trap  tuff. — Small  angular  fragments  of  the  scoriae  and 
pumice,  above  mentioned,  and  the  dust  of  the  same,  produced  by  volcanic 
explosions,  form  the  tuffs  which  abound  in  all  regions  of  active  vol- 
canoes, where  showers  of  these  materials,  together  with  small  pieces  of 
other  rocks  ejected  from  the  crater,  fall  down  upon  the  land  or  into  the 
sea.  Here  they  often  become  mingled  with  shells,,  and  are  stratified. 
Such  tuffs  are  sometimes  bound  together  by  a  calcareous  cement,  and 
form  a  stone  susceptible  of  a  beautiful  polish.  But  even  when  little  or  no 
lime  is  present,  there  is  a  great  tendency  in  the  materials  of  ordinary 
tuffs  to  cohere  together.  Besides  the  peculiarity  of  their  composition, 
some  tuffs,  or  volcanic  grits,  as  they  have  been  termed,  differ  from  ordi- 
nary sandstones  by  the  angularity  of  their  grains,  and  they  often  fass  into 
volcanic  breccias. 

According  to  Mr.  Scrope,  the  Italian  geologists  confine  the  term  tuff,  or 
tufa,  to  felspathose  mixtures,  and  those  composed  principally  of  pumice, 
using  the  term  peperino  for  the  basaltic  tuffs.*  The  peperinos  thus  dis- 
tinguished are  usually  brown,  and  the  tuffs  gray  or  white. 

We  meet  occasionally  with  extremely  compact  beds  of  volcanic  ma- 
terials, interstratified  with  fossiliferous  rocks.  These  may  sometimes  be 
tuffs,  although  their  density  or  compactness  is  such  as  to  cause  them 
to  resemble  many  of  those  kinds  of  trap  which  are  found  in  ordinary 
dikes.  The  chocolate-colored  mud,  which  was  poured  for  weeks  out 
of  the  crater  of  Graham's  Island  in  the  Mediterranean,  in  1831,  must, 
when  unmixed  with  other  materials,  have  constituted  a  stone  heavier 
than  granite.  Each  cubic  inch  of  the  impalpable  powder  which  has 
fallen  for  days  through  the  atmosphere,  during  some  modem  erup- 
tions, has  been  found  to  weigh,  without  being  compressed,  as  much 
as  ordinary  trap-rocks,  and  to  be  often  identical  with  these  in  mineral 
composition. 

Palagonite-tuff. — The  nature  of  volcanic  tuffs  must  vary  according 
to  the  mineral  composition  of  the  ashes  and  cinders  thrown  out  of 
each  vent,  or  from  the  same  vent,  at  different  times.  In  descrip- 
tions of  Iceland,  we  read  of  Palagonite-tuffs  as  very  common.  The 
name  Palagonite  was  first  given  by  Professor  Bunsen  to  a  mineral 
occurring  in  the  volcanic  formations  of  Palagonia,  in  Sicily.  It  is 
rather  a  mineral  substance  than  a  mineral,  as  it  is  always  amorphous, 
and  has  never  been  found  crystallized.  Its  composition  is  variable, 
but  it  may  be  defined  as  a  hydrosilicate  of  alumina,  containing  oxide 
of  iron,  lime,  magnesia,  and  some  alkali.  It  is  of  a  brown  or  black- 
ish-brown color,  and  its  specific  density,  2*43.  It  enters  largely  into 
the  composition  of  volcanic  tuffs  and  breccias,  and  is  considered  by 
Bunsen  as  an  altered  rock,  resulting  from  the  action  of  steam  on  vol- 
canic tuffs. 

*  Geol.  Trans.  2d  series,  vol.  ii.  p.  211. 


Cn.  XXVm.]  AGGLOMERATE — LATERITE.  471 

Agglomerate. — In  the  neighborhood  of  volcanic  vents,  we  frequently 
observe  accumulations  of  angular  fragments  of  rock,  formed  during 
eruptions  by  the  explosive  action  of  steam,  which  shatters  the  subjacent 
stony  formations,  and  hurls  them  up  into  the  air.  They  then  fall  in 
showers  around  the  cone  or  crater,  or  may  be  spread  for  some  distance 
over  the  surrounding  country.  The  fragments  consist  usually  of  different 
varieties  of  scoriaceous  and  compact  lavas  ;  but  other  kinds  of  rock,  such 
as  granite,  or  even  fossiliferous  limestones,  may  be  intermixed  ;  in  short, 
any  substance  through  which  the  expansive  gases  have  forced  their  way. 
The  dispersion  of  such  materials  may  be  aided  by  the  wind,  as  it  varies 
in  direction  or  intensity,  and  by  the  slope  of  the  cone  down  which  they 
roll,  or  by  floods  of  rain,  which  often  accompany  eruptions.  But  if  the 
power  of  running  water,  or  of  the  waves  and  currents  of  the  sea,  be  suffi- 
cient to  carry  the  fragments  to  a  distance,  it  can  scarcely  fail  (unless 
where  ice  intervenes)  to  wear  off  their  .ingles,  and  \he  formation  then 
becomes  a  conglomerate.  If  occasionally  globular  pieces  of  scoriae 
abound  in  an  agglomerate,  they  do  not  owe  their  rounded  form  to  at- 
trition. 

The  size  of  the  angular  stones  in  some  agglomerates  is  enormous  ;  for 
they  may  be  two  or  three  yards  in  diameter.  The  mass  is  often  50  or 
100  feet  thick,  without  showing  any  marks  of  stratification.  The  term 
volcanic  breccia  may  be  restricted  to  those  tuffs  which  are  made  up  of 
small  aLgular  pieces  of  rock. 

The  slaggy  crust  of  a  stream  of  lava  will  often,  while  yet  in  motion, 
split  up  into  angular  pieces,  some  of  which,  after  the  current  has  ceased 
to  flow,  may  be  seen  to  stick  up  five  or  six  feet  above  the  general  surfaoe- 
Such  broken-up  crusts  resemble  closely  in  structure  the  agglomerates 
above  described,  although  the  composition  of  the  materials  will  usually 
be  more  homogeneous. 

Laterite  is  a  red,  jaspery,  or  brick-like  rock,  composed  of  silicate  of 
alumina  and  oxide  of  iron.  The  red  layers,  called  "  ochre-beds,"  dividing 
the  lavas  of  the  Giant's  Causeway,  are  laterites.  These  were  found  by 
Delesse  to  be  trap  impregnated  with  the  red  oxide  of  iron,  and  in  part 
reduced  to  kaolin.  When  still  more  decomposed,  they  were  found  to  be 
clay  colored  by  red  ochre.  As  two  of  the  lavas  of  the  Giant's  Causeway 
are  parted  by  a  bed  of  lignite,  it  is  not  improbable  that  the  layers  of 
laterite  seen  in  the  Antrim  cliffs  resulted  from  atmospheric  decomposi- 
tion. In  Madeira  and  the  Canary  Islands,  streams  of  lava  of  subaerial 
origin  are  often  divided  by  red  bands  of  laterite,  probably  ancient  soils 
formed  by  the  decomposition  of  the  surfaces  of  lava-currents,  many  of 
these  soils  having  been  colored  red  in  the  atmosphere  by  oxide  of  iron, 
others  burnt  into  a  red  brick  by  the  overflowing  of  heated  lavas.  These 
red  bands  are  sometimes  prismatic,  the  small  prisms  being  at  right  angles 
to  the  sheets  of  lava.  Red  clay  or  red  marl,  formed  as  above  stated  by 
the  disintegration  of  lava,  scoriae,  or  tuff,  has  often  accumulated  to  a 
great  thickness  in  the  valleys  of  Madeira,  being  washed  into  them  by 
alluvial  action ;  and  some  of  the  thick  beds  of  laterite  in  India  may  have 


472  MINERAL  COMPOSITION  [On.  XXVIIL 

had  a  similar  origin.     In  India,  however,  especially  in  the  Deccan,  the 
term  "  laterite"  seems  to  have  been  used  too  vaguely. 

It  would  be  tedious  to  enumerate  all  the  varieties  of  trap  and  lava 
which  have  been  regarded  by  different  observers  as  sufficiently  abundant 
to  deserve  distinct  names,  especially  as  each  investigator  is  too  apt  to 
exaggerate  the  importance  of  local  varieties  which  happen  to  prevail  in 
districts  best  known  to  him.  It  will  be  useful,  however,  to  subjoin  here, 
in  the  form  of  a  glossary,  an  alphabetical  list  of  the  names  and  synonyms 
most  commonly  in  use,  with  brief  explanations,  to  which  I  have  added  a 
table  of  the  analysis  of  the  simple  minerals  most  abundant  in  the  volcanic 
and  hypogene  rocks. 


Explanation  of  the  Names,  Synonyms,  and  Mineral  Composition  of  the 
more  abundant  Volcanic  Rocks. 

AGGLOMERATE.  A  coarse  breccia,  composed  of  fragments  of  rock,  cast  out  .  f 
volcanic  vents,  for  the  most  part  angular  and  without  any  admixture  of 
water-worn  stones.  "  Volcanic  conglomerates  "  may  be  applied  to  mix- 
tures in  which  water-worn  stones  occur. 

APHANITE.    See  Cornean. 

AMPHIBOLITE,  or  HORNBLENDE  ROCK,  which  see. 

AMYGDALOID.     A  particular  form  of  volcanic  rock  ;  see  p.  468. 

AUGITE  ROCK.  A  rock  of  the  basaltic  family,  composed  of  felspar  and  augite. 
See  p.  466. 

AUGITIC-PORPHYRY.  Crystals  of  Labrador-felspar  and  of  Augite,  in  a  green  or 
dark  gray  base.  (Rose,  Ann.  des  Mines,  torn.  8,  p.  22,  1835.) 

BASALT.     An  intimate  mixture  of  felspar  and  augite  with  magnetic  iron,  olivine, 

<fec.     See  p.  466. 
BASANITE.     Name  given  by  Alex.  Brongniart  to  a  rock,  having  a  base  of  basalt, 

with  more  or  less  distinct  crystals  of  augite  disseminated  through  it. 

CLAYSTONE  and  CLAYSTONE-PORPHYRY.  An  earthy  and  compact  stone,  usually  of 
a  purplish  color,  like  an  indurated  clay  ;  passes  into  hornstone  ;  generally 
contains  scattered  crystals  of  felspar  and  sometimes  of  quartz. 

CLINKSTONE.  Syn.  Phonolite,  fissile  Petrosilex,  see  p.  467  ;  a  grayish-blue  rock, 
having  a  tendency  to  divide  into  slabs  ;  hard,  with  clean  fracture,  ringing 
under  the  hammer ;  principally  composed  of  felspar,  and,  according  to 
Gmelin,  of  felspar  and  mesotype.  (Leonhard,  Mineralreich,  p.  102.) 

COMPACT  FELSPAR,  which  has  also  been  called  Petrosilex ;  the  rock  so  called 
includes  the  hornstone  of  some  mineralogists,  is  allied  to  clinkstone,  but  is 
harder,  more  compact,  and  translucent.  It  is  a  varying  rock,  of  which  the 
chemical  composition  is  not  well  defined.  (MacCulloch's  Classification  of 
Rocks,  p.  481.) 

CORNEAN  or  APHANITE.  A  compact  homogeneous  rock  without  a  trace  of  crystal- 
lization, breaking  with  a  smooth  surface  like  some  compact  basalts  ;  con- 
sists of  hornblende,  quartz,  and  felspar,  in  intimate  combination.  It 
derives  its  name  from  the  Latin  word  cornu,  horn,  in  allusion  to  its 
toughness  and  compact  texture. 

DIALLAGE  ROCK.  Syn.  Euphotide,  Gabbro,  and  some  Ophiolites.  Compounded 
of  felspar  and  diallage. 


CH.  XXVIII.]  OF   VOLCANIC   EOCKS.  473 

DIORITE.  A  kind  of  Greenstone,  which  see.  Components,  felspar  and  horn 
blende  in  grains.  According  to  Rose,  Ann.  des  Mines,  torn.  8,  p.  4,  dioritt 
consists  of  albite  and  hornblende,  but  Delesse  has  shown  that  the  felspar 
may  be  Oligoclase  or  Labradorite.  (Ann.  des  Mines,  1849,  torn.  16,  p. 
323.)  Its  dark  color  is  due  to  disseminated  plates  of  hornblende.  Set 
above,  p.  46*7. 

DOLERITE.  According  to  Rose  (ibid.  p.  32),  its  composition  is  black  augite  and 
Labrador- felspar ;  according  to  Leonhard  (Mineralreick,  <fcc.,  p.  77),  augite, 
Labrador-felspar,  and  magnetic  iron.  See  above,  p.  466. 

DOMITS.     An  earthy  trachyte,  found  in  the  Puy  de  Dome,  in  Auvergne. 

EUPHOTIDE.  A  mixture  of  grains  of  Labrador-felspar  and  diallage.  (Rose,  ibid. 
p.  19.)  According  to  some,  this  rock  is  defined  to  be  a  mixture  of  augite 
or  hornblende  and  Saussurite,  a  mineral  allied  to  jade.  (Allan's  Mine- 
ralogy, p.  158.)  Haidinger  first  observed  that  in  this  rock  hornblende 
surrounds  the  crystals  of  diallage. 

FELSPAR-PORPHYRY.  Syn.  Hornstone -porphyry ;  a  base  of  felspar,  with  crystals 
of  felspar,  and  crystals  and  grains  of  quartz.  See  also  Hornstone. 

GABBRO,  see  Diallage  rock. 

GREENSTONE.     Syn.  A  mixture  of  felspar  and  hornblende.    See  above,  p.  467. 

GRAYSTONE.     (Graustein  of  Werner.)     Lead-gray  and  greenish  rock  composed  of 

felspar  and  augite,  the  felspar  being  more  than  seventy-five  per  cent. 

(Scrope,  Journ.  of  Sci.  No.  42,  p.  221.)     Graystone  lavas  are  intermediate 

in  composition  between  basaltic  and  trachytic  lavas. 

HORNBLENDE  RCCK,  or  AMPHIBOLITE.  This  rock,  as  defined  by  Leonhard,  is  com- 
posed entirely  of  hornblende ;  but  such  a  rock  appears  to  be  exceptional, 
and  confined  to  mineral  veins.  Any  rocks  in  which  hornblende  plays  a 
conspicuous  part,  constituting  the  "roches  amphiboliques"  of  French 
writers,  may  be  called  hornblende  rock.  They  always  contain  more  or 
less  felspar  in  their  composition,  and  pass  into  basalt  or  greenstone,  or 
aphanite.  See  p.  466. 

HORNSTONE-PORPHYRY.  A  kind  of  felspar  porphyry  (Leonhard,  loc.  cit.)  with  a 
base  of  hornstone,  a  mineral  approaching  near  to  flint,  differing  from  com- 
pact felspar  in  being  infusible. 

HYPERSTHENE  ROCK,  a  mixture  of  grains  of  Labrador-felspar  and  hypersthene 
(Rose,  Ann.  des  Mines,  torn.  8,  p.  13),  having  the  structure  of  syenite  or 
granite ;  abundant  among  the  traps  of  Skye.  It  is  extremely  tough, 
grayish,  and  greenish  black.  Some  geologists  consider  it  a  greenstone,  in 
which  hypersthene  replaces  hornblende ;  and  this  opinion,  says  Delesse, 
is  borne  out  by  the  fact  that  hornblende  usually  occurs  in  hyparsthene 
rock,  often  enveloping  the  crystals  of  hypersthene.  The  latter  have  a 
pearly  or  metallic-pearly  lustre. 

LATERITE.  A  red,  jaspery,  brick-like  rock,  composed  of  silicate  of  alumina  and 
oxide  of  iron,  or  sometimes  consisting  of  clay  colored  with  red  ochre.  See 
above,  p.  471. 

MELAPHYRE.  A  variety  of  black  porphyry  composed  of  Labrador-felspar  and  a 
small  quantity  of  augite.  Its  black  color  was  formerly  attributed  to  dis- 
seminated microscopic  crystals  of  augite,  but  M.  Delesse  has  shown  that 
the  paste  is  discolored  by  hydrochloric  acid,  whereas  this  acid  does  not 
attack  the  crystals  of  augite,  which  are  seen  to  be  isolated,  and  few  in 
number.  (Ann.  des  Mines,  4th  ser.  torn.  xii.  p.  228.)  From  /ifAaj,  melas, 
black 


474  MINERAL   COMPOSITION  [On.  XXVIIJ 

OBSIDIAN.    Vitreous  lava  like  melted  glass,  nearly  allied  to  pitchstone. 

OPHIOLJ-FE.     A  name  given  by  Al.  Brongniart  to  serpentine. 

OPHITE.  A  name  given  by  Palassou  to  certain  trap  rocks  of  the  Pyrenees,  very 
variable  in  composition,  usually  composed  of  Labrador-felspar  and  horn- 
blende, and  sometimes  augite,  occasionally  of  a  green  color,  and  passing 
into  serpentine. 

PALAGONITE  TUFF.  An  altered  volcanic  tuff  containing  the  substance  termed  pa- 
lagonite.  See  p.  470. 

PEARLSTONE.  A  volcanic  rock,  having  the  lustre  of  mother  of  pearl ;  usually 
having  a  nodular  structure ;  intimately  related  to  obsidian,  but  less  glassy. 

PEPERINO.     A  form  of  volcanic  tuff,  composed  of  basaltic  scoriae.     See  p.  470. 

PETROSILEX.     See  Clinkstone  and  Compact  Felspar. 

PHONOLITE.     Syn.  of  Clinkstone,  which  see. 

PITCHSTONE,  or  KETINITE,  of  the  French.  Vitreous  lava,  less  glassy  than  obsidian ; 
a  blackish  green  rock  resembling  glass,  having  a  resinous  lustre  and  ap- 
pearance of  pitch  ;  composition  usually  of  glassy  felepar  (orthoclase)  with 
a  little  mica,  quartz,  and  hornblende  ;  in  Arran  it  forms  a  dike  thirty  feet 
wide,  cutting  through  sandstone. 

PUMICE.     A  light,  spongy,  fibrous  form  of  trachyte.     See  p.  469. 

PrROXENic-PORPHYRT,  same  as  augitic-porphyry,  pyroxene  being  Haiiy's  name  for 
augite. 

SCORLE.  Syn.  volcanic  cinders ;  reddish  brown  or  black  porous  form  of  lava. 
See  p.  469. 

SERPENTINE.  A  greenish  rock  in  which  there  is  much  magnesia.  Its  composition 
always  approaches  very  near  to  the  mineral  called  "  noble  serpentine" 
(see  Table  of  Ayalyses,  p.  475),  which  forms  veins  in  this  rock.  The  mine- 
rals most  commonly  found  in  Serpentine  are  diallage,  garnet,  chlorite, 
oxydulous  iron,  and  chromate  of  iron.  The  diallage  and  garnet  occurring 
in  serpentine  are  richer  in  magnesia  than  when  they  are  crystallized  in 
other  rocks.  (Delesse  Ann.  des  Mines,  1851,  torn,  xviii.  p.  309).  Occurs 
sometimes,  though  rarely,  in  dikes,  altering  the  contiguous  strata ;  is  in- 
differently a  member  of  the  trappean  or  hypogene  series.  Its  absence 
from  recent  volcanic  products  seems  to  imply  that  it  belongs  properly  to 
the  metamorphic  class;  and,  even  when  it  is  found  in  dikes  cutting 
through  aqueous  formations,  it  may  be  an  altered  basalt,  which  abounded 
greatly  in  olivine. 

TEPHRINE,  synonymous  with  lava.  Name  proposed  by  Alex.  Brongniart. 
TOADSTONE.  A  local  name  in  Derbyshire  for  a  kind  of  wacke,  which  see. 
TRACHYTE.  Chiefly  composed  of  glassy  felspar,  with  crystals  of  glassy  felspar. 

See  p.  466. 

TRAP  TUFF.     See  p.  470. 
TRASS.     A  kind  of  tuff  or  mud  poured  out  by  lake-craters  during  eruptions ; 

common  in  the  Eifel,  in  Germany. 
TUFF.     Syn.  Trap-tuff,  volcanic  tuff.     See  p.  470. 

VITREOUS  LAVA.     See  Pitchstone  and  Obsidian. 
VOLCANIC  TUFF.     See  p.  470. 

WACKE.     A  soft  and  earthy  variety  of  trap,  having  an  argillaceous  aspect.     It 
resembles  indurated  clay,  and  when  scratched,  exhibits  a  shining  streak. 
WHINSTONE.    A  Scotch  provincial  term  for  greenstone  and  other  hard  trap  rocks. 


OH.  XXVJII] 


OF  VOLCANIC  EOCKS. 


475 


ANALYSIS    OF   MINERALS    MOST    ABUNDANT    IN    THE    VOLCANIC    AND 
HYPOGENE    ROCKS. 


Silica 

Alu- 
mina 

Mag- 
ncsia. 

Lime. 

Potash. 

Soda. 

Iron 

Oxide. 

Man- 
g-anese. 

Remainder. 

3- 
10-80 

1-00 

43-05  C. 
0-27  W. 
12-20  W. 
11-55  W. 
8-96  W. 

0-85  W. 
0-30  Ch. 
0-22  W. 

0-5  W. 

1-5  F. 

1-50  loss. 

1-     W. 

9-83  W. 
12-30  W. 

1-63  T. 
2-00  F. 
1-58  F. 
0-90  loss. 
0-22  F. 
1-51  loss. 
3.59  L. 
3-28  F. 

0-11  P. 

4-18  loss. 
4;12 

12-45  W. 
13-70  W. 
1070  W. 
5-22  W. 
5'     W. 
3-83  W. 

0-12  P. 
7-66  B. 
2  -09  loss. 
1-49  F. 
0-22  Ph. 
3-56  B. 
0-41  L. 
2-70  F. 
1   3-77  loss. 
C  4-02  B. 

Actinolite  (Bergman)       ... 
Augite,   black,    of  volcanic  rocks 
(Klaprotb). 

48-00 

5-00 

8-75 

24-00 
56-33 

-    ' 

-    - 

Chiastolite  (Landgrabe)    - 
Chlorite  (Kobell)       - 

68-50 
31-14 
31-07 
25-37 

49-30 
56-81 

37' 
6675 
6491 
68-84 
71-50 

58-91 

55-75 
53-20 

63-25 
62-87 
35-75 

30-11 
17-14 
15-47 
28-79 

5-50 
2*07 

21- 

17-5 
19-16 
20-53 
15-50 

24-59 

265 
27-31 

23-92 
22-91 

27-25 
16- 
12- 
12-18 
8-23 

2-25 

24-62 
1-38 

19-70 

21-.y 

11  -a 

35- 
12-67 
13-92 
19-80 

33-61 
33-03 

0-25 
0-42 
0-92 

33-09 

41-83 
34-75 

1-13 
34-40 
19-14 
17-09 

17-61 
29-68 

0-65 
0-50 
0*40 

i-oi 

0-32 

traces 

3-85 
19-99 
28-79 

9-43 
8-46 

24- 
0-75 
traces 

traces 
0-99 

1-25 
1-03 

traces 
1-89 

36- 
16- 
30- 
7-32 
16-15 

24-5 
8-53 

22- 
7* 
19-03  S. 
21-31  S. 
5-03  P. 
1-61 

3-48  S. 
11-72 
12- 
18-5 

1-17 
1-69 
7-39 
1-40 

r? 

2.5 

9-33  S. 
6-19  P. 

17-44 

0-53 

traces 

0-51 
0-62 

1'5 

0-25 

0-25 
0-22 
traces 

a  trace 

2-" 

15-70 
|l-09 

o-io 

1-40 

traces 
0-43 

traces 

1  • 

97'  S. 
1-89 

0-46 

15-43 
2-20 

15- 
1-25 
0-78 
a  trace 
1-73 

4-01 

11- 

8-02 

3-23 
3-61 

12-  ~ 
11-07 

3-16 
2-53 

3-40 
2-31 
1-39 

2-49 
9-12 
5-94 

7-59 

4- 

3-52 

6-88 
8-16 

trapp). 
Diallage  of  euphotide  (Delesse) 
of  bronzite  from  the  Tyrol 
(Kohler). 
Epidote  (Yauquelin) 
Felspar,  common  (Rose) 

AlDllC  (rtOSCJ       ^             ^  ^^ 

the  Vosges  (Delesse). 

the  Tosges  (Delesse).  ' 

ijuDrai  jriic  ^jYiaproinj 

(Delesse). 

from  Mont  Blanc  (Delesse). 

(Scheerer). 
Garnet  (Klaproth)     .... 

(Phillips)        - 
Hornblende  (Klaproth)    - 

43' 
42- 

45-69 

tj-m 

54-25 
5375 
53-42 

54-64 

46-80 
42.5 
50- 

40-00 
41-22 
37'54 

49-06 

46-23 
40-86 
50- 
41-0 

43-07 

41-58 

40-aa 

M-85 

64- 
61-75 
61-75 

37-00 

41*16 
35-48 

2-25 
18'79 
18-40 

14- 

14-95 

9- 

0-63 
4-70 
30-32 

0-41 

2-10 
47-35 
38-5 
38-5 

40-37 
42-61 
37-98 
28-53 
22- 
31-68 
30-5 

2-58 

0-61 
4-68 

20- 
11- 
13-85 
7-05 

1-5 
21-72 

1-61 
9-87 

1-33 

2-58 
0-70 

0-25 

a  trace 
0-14 

2\-35 

10-" 
S'Bl 
6-05 

7-17 

4-19 
8-87 

0-65 

15-09 
5-40 

1-40  { 

i-oo 

1-45 

^P  onsoor  ) 

from  Corsica  (Delesse). 
Hypersthene  (Klaproth) 
Leucite  (Klaproth)    - 
Malacolite  or  Sahlite,   green  (De- 
lesse). 
Mesotype  (Gehlen)    .... 
(Berzelius)    - 

Mica  (KlaprothT        - 
(Vauquelin)        .... 

black  (H.  Rose) 
green,  of  protogine  (Delesse)    - 

reddish,    of  crystalline  lime- 
stone (Delesse). 

rose-colored,    of   granite    (C. 
Gmelin). 

white,  of  pegmatite  (Delesse) 
Olivine  (Berzelius)    ... 
(Klaproth) 

roth). 
Serpentine  (Hi  singer) 
asbestitbrm  (Delesse) 
*  common  (Delesse) 
Steatite  (Delesse)      ... 

0-5 
1-50 

O'oO 

275 
065 

2-17 
0-48 

1-39  £ 

1-37 
1-75 

Talc,  pure  (Delesse) 
:  (Klaproth)         ... 

Tourmaline    or    Schorl,    black,   of 
granite  from  Devon  (Rammels- 
berg). 

ravia  (Rammelsberg). 
Tourmaline  (Gmelin) 

In  the  last  column  of  the  above  Table,  the  following  signs  are  used  :  B.  Boracic  acid,  C.  Carbonic  acid 
Ch.  Oxide  of  Chrome,  F.  Fluoric  acid,  L.  Lithine,  P.  Phosphoric  acid,  T.  Oxide  of  Titanium,  W.  Water 
In  th*  7th  column  of  numbers,  P.  means  Protoxide,  and  S.  Sesquioxide. 


470 


TKAP  DIKES. 


[Ca.  XXLSL 


CHAPTER  XXIX. 


VOLCANIC  ROCKS — continued. 

Trap  dikes — sometimes  project — sometimes  leave  fissures  vacant  by  decomposi- 
tion— Branches  and  veins  of  trap — Dikes  more  crystalline  in  the  centre — 
Strata  altered  at  or  near  the  contact — Obliteration  of  organic  remains — Con- 
version of  chalk  into  marble — Trap  interposed  between  strata — Columnar  and 
globular  structure — Relation  of  trappean  rocks  to  the  products  of  active  vol- 
canoes— Form,  external  structure,  and  origin  of  volcanic  mountains — Craters 
and  Calderas — Sandwich  Islands — Lava  flowing  underground — Truncation  of 
cones — Javanese  calderas — Canary  Islands — Structure  and  origin  of  the  Cal- 
dera  of  Palma — Older  and  newer  volcanic  rocks  in,  unconformable — Aqueous 
conglomerate  in  Palma — Hypothesis  of  upheaval  considered — Slope  on  which 
stony  lavas  may  form — Extent  and  nature  of  aqueous  erosion  in  Palma — Island 
of  St.  Paul  in  the  Indian  Ocean — Peak  of  Teneriffe,  and  ruins  of  older  cone — 
Madeira — Its  volcanic  rocks,  partly  of  marine,  and  partly  of  subaerial  origin — 
Central  axis  of  eruptions — Varying  dip  of  solid  lavas  near  the  axis,  and  further 
from  it — Leaf-bed,  and  fossil  land-plants — Central  valleys  of  Madeira  not 
craters,  or  calderas. 

HAVING  in  the  last  chapter  spoken  of  the  composition  and  mineral 
characters  of  volcanic  rocks,  I  shall  next  desciibe  the  manner  and  position 
in  which  they  occur  in  the  earth's  crust,  and  their  external  forms.  The 
leading  varieties  both  of  the  basaltic  aad  trachytic  rocks,  as  well  as  of 
greenstone  and  the  rest,  are  found  sometimes  in  dikes  penetrating  strati- 
fied and  unstratified  formations,  sometimes  in  shapeless  masses  protruding 
through  or  overlying  them,  or  in  horizontal  sheets  intercalated  between 
strata. 

Volcanic  or  trap  dikes. — Fissures  have  already  been  spoken  of  as  oc- 
curring in  all  kinds  of  rocks,  some  a  few  feet,  others  many  yards  in  width, 
and  often  filled  up  with  earth  or  angular  pieces  of  stone,  or  with  sand  and 
pebbles.     Instead  of  such  ma- 
terials, suppose  a  quantity  of  Fig.  624. 
melted  stone  to  be  driven  or 
injected  into  an  open  rent,  and 
there  consolidated,  we  have  then 
a  tabular  mass  resembling   a 
wall,  and  called  a  trap  dike. 
It  is  not  uncommon  to  find  such 
dikes  passing  through  strata  of 
soft  materials,   such    as    tuff, 
scoriae,  or  shale,  which,  being 
more  perishable  than  the  trap, 
are  often  washed  away  by  the 

T_.   i  Bike  in  valley,  near  Brazen  Head,  Madeira. 

6ea,   rivers,   Or    ram,    in    which  (From  a  drawing  of  Capt.  Basil  Hall,  E.  N.) 


CH.  XXIX.] 


TEAP   DIKES  AND  VEINS. 


477 


Fig.  625. 


case  the  dike  stands  prominently  out  in  the  face  of  precipices,  or  on  the 
level  surface  of  a  country. 

In  the  islands  of  Arran  and  Skye,  and  in  other  parts  of  Scotland,  where 
sandstone,  conglomerate,  and  other  hard  rocks  are  traversed  by  dikes 
of  trap,  the  converse  of  the  above  phenomenon  is  seen.  The  dike, 
having  decomposed  more  rapidly  than  the  containing  rock,  has  once 
more  left  open  the  original  fissure,  often  for  a  distance  of  many  yards 
inland  from  the  sea-coast,  as  represented 
in  the  annexed  view  (fig.  625).  In  these 
instances,  the  greenstone  of  the  dike  is 
usually  more  tough  and  hard  than  the 
sandstone ;  but  chemical  action,  and 
chiefly  the  oxidation  of  the  iron,  has 
given  rise  to  the  more  rapid  decay. 

There  is  yet  another  case,  by  no  means 
uncommon  in  Arran  and  other  parts  of 
Scotland,  where  the  strata  in  contact  with 
the  dike,  and  for  a  certain  distance  from 
it,  have  been  hardened,  so  as  to  resist  the 
action  of  the  weather  more  than  the  dike 
itself,  or  the  surrounding  rocks.  When 
this  happens,  two  parallel  walls  of  indu- 
rated strata  are  seen  protruding  above 
the  general  level  of  the  country  and  following  the  course  of  the  dike. 

As  fissures  sometimes  send  off  branches,  or  divide  into  two  or  more 
fissures  of  equal  size,  so  also  we  find  trap  dikes  bifurcating  and  ramifying, 
and  sometimes  they  are  so  tortuous  as  to  be 
called  veins,  though  this  is  more  common 
in  granite  than  in  trap.  The  accompany- 
ing sketch  (fig.  626)  by  Dr.  MacCulloch 
represents  part  of  a  sea-cliff  in  Argyleshire, 
where  an  overlying  mass  of  trap,  6,  sends 
out  some  veins  which  terminate  downwards. 
Another  trap  vein,  a  a,  cuts  through  both 
the  limestone,  c,  and  the  trap,  b. 

In  fig.  627,  a  ground  plan  is  given  of  a 


Fissures  left  vacant  by  decomposed 
trap.  Strathaird,  Skye.  (MacCul- 
loch.) 


Fig.  626. 


Trap  veins  in  Airdnamurchan. 


ramifying  dike  of  greenstone,  which  I  observed  cutting  through  sandstone 
on  the  beach  near  Kildonan  Castle,  in  Arran.    The  larger  branch  varies 


Fig.  627. 


Ground  plan  of  greenstone  dike  traversing  sandstone.    Arran. 


4YS  VARIOUS  FOEMS  OF  [On.  XXIX. 

from  5  to  7  feet  in  width,  which  will  afford  a  scale  of  measurement  for 
the  whole. 

In  the  Hebrides  and  other  countries,  the  same  masses  of  trap  which 
occupy  the  surface  of  the  country  far  and  wide,  concealing  the  subjacent 
stratified  rocks,  are  seen  also  in  the  sea  cliffs,  prolonged  downwards  in 
veins  or  dikes,  which  probably  unite  with  other  masses  of  igneous  rock 
at  a  greater  depth.  The  largest  of  the  dikes  represented  in  the  annexed 
diagram,  and  which  are  seen  in  part  of  the  coast  of  Skye,  is  no  less  than 
100  feet  in  width. 

Fig.  628. 


Trap  dividing  and  covering  sandstone  near  Suishnish  in  Skye.    (MacCnlloch.) 

Every  variety  of  trap-rock  is  sometimes  found  in  dikes,  as  basalt,  green- 
stone, felspar-porphyry,  and  trachyte.  The  amygdaloidal  traps  also 
occur,  though  more  rarely,  and  even  tuff  and  breccia,  for  the  materials  of 
these  last  may  be  washed  down  into  open  fissures  at  the  bottom  of  the 
sea,  or  during  eruptions  on  the  land  may  be  showered  into  them  from 
the  air. 

Some  dikes  of  trap  may  be  followed  for  leagues  uninterruptedly  in 
nearly  a  straight  direction,  as  in  the  north  of  England,  showing  that  the 
fissures  which  they  fill  must  have  been  of  extraordinary  length. 

In  many  cases  trap  at  the  edges  or  sides  of  the  dike  is  less  crystalline 
or  more  earthy  than  in  the  centre,  in  consequence  of  the  melted  matter 
having  cooled  more  rapidly  by  coming  in  contact  with  the  cold  sides  of 
the  fissure  ;  whereas,  in  the  centre,  where  the  matter  of  the  dike  is  kept 
longer  in  a  fluid  or  soft  state,  crystals  are  slowly  formed.  But  I  observed 
the  converse  of  the  above  phenomena  in  Teneriffe,  in  the  neighborhood 
of  Santa  Cruz,  where  a  dike  is  seen  cutting  through  horizontal  beds 
of  scoriae  in  the  sea-cliff  near  the  Barranco  de  Bufadero.  It  is  ver- 
tical in  its  main  direction,  slightly  flexuous,  but  about  one  foot 
thick.  On  each  side  are  walls  of  compact  basalt,  but  in  the  centre 
the  rock  is  highly  vesicular  for  a  width  of  about  4  inches.  In 
this  instance,  the  fissure  may  have  become  wider  after  the  lava  on 
each  side  had  consolidated,  and  the  additional  melted  matter  poured 
into  the  middle  space  may  have  cooled  more  rapidly  than  that  at 
the  sides. 

In  the  ancient  part  of  Vesuvius,  called  Somma,  a  thin  band  of  half- 
vitreous  lava  is  found  at  the  edge  of  some  dikes.  At  the  junction 
of  greenstone  dikes  with  limestone,  a  sahlband,  or  selvage,  of  serpen- 
tine is  occasionally  observed.  On  the  left  shore  of  the  fiord  of  Christi- 
ania,  in  Norway,  I  examined,  in  company  with  Professor  Keilhau, 
a  remarkable  dike  of  syenitic  greenstone,  which  is  traced  through 
Silurian  strata,  until  at  length,  in  the  promontory  of  Naesodden,  it 


CH.  XXIX.] 


TRAP   DIKES  AND  VEINS. 


479 


Green- 
stone. 


Imbedded  fragment  of  crystalline  schist  sur- 
rounded by  a  band  of  greenstone. 


enters  mica-schist.     Fig.  629  rep-  Fis- 6'29- 

resents  a  ground  plan,  where  the  tic  green^tone^of  ^sodden, 

dike  appears  8  paces  in  width.     In 

the  middle  it  is  highly  crystalline 

and  granitiform,  of  a  purplish  color, 

and  containing  a  few  crystals  of 

mica,  and  strongly  contrasted  with 

the   whitish  mica-schist,  between 

which  and  the  syenitic  rock  there 

is  usually  on  each  side  a  distinct 

black  band,    18   inches   wide,   of 

dark  greenstone.     When  first  seen, 

these  bands  have  the  appearance 

of  two  accompanying  dikes;   yet  they  are,  in  fact,  only  the  different 

form  which   the   syenitic   materials   have   assumed  where   near  to   or 

in  contact  with  the  mica-schist.     At  one  point,  a,  one  of  the  sahlbands 

terminates    for    a    space ;    but  near   this   there   is    a   large    detached 

block,  6,  having  a  gneiss-like  structure,  consisting  of  hornblende   and 

felspar,  which  is  included  in  the  midst  of  the  dike.     Round  this  a 

smaller  encircling  zone  is  seen,  of  dark  basalt,  or  fine-grained  greenstone, 

nearly  corresponding  to  the  larger  ones  which  border  the  dike,  but  only 

one  inch  wide. 

It  seems  therefore  evident  that  the  fragment,  6,  has  acted  on  the  mat- 
ter of  the  dike,  probably  by  causing  it  to  cool  more  rapidly,  in  the  same 
manner  as  the  walls  of  the  fissure  have  acted  on  a  larger  scale.  The 
facts  also  illustrate  the  facility  with  which  a  granitiform  syenite  may 
pass  into  ordinary  rocks  of  the  volcanic  family. 

The  fact  above  alluded  to,  of  a  foreign  fragment,  such  as  6,  fig.  629, 
included  in  the  midst  of  the  trap, 
as  if  torn  off  from  some  subjacent 
rock  or  the  walls  of  a  fissure,  is 
by  no  means  uncommon.  A  fine 
example  is  seen  in  another  dike 
of  greenstone,  10  feet  wide,  in 
the  northern  suburbs  of  Chris- 
tiania,  in  Norway,  of  which  the 
annexed  figure  is  a  ground  plan. 
The  dike  passes  through  shale, 

known    bv   its    fossils    to    belono*  Greenstone  dike,  with  fragments  of  gneiss. 

*  Sorgenfria,  Christiania. 

to   the   Silurian   series.      In   the 

black  base  of  greenstone  are  angular  and  roundish  pieces  of  gneiss,  some 
white,  others  of  a  light  flesh-color,  some  without  lamination,  like  granite, 
others  with  laminae,  which,  by  their  various  and  often  opposite  direc- 
tions, show  that  they  have  been  scattered  at  randon  through  the 
matrix.  These  imbedded  pieces  of  gneiss  measure  from  1  to  about  8 
inches  in  diameter. 

Rocks  altered  by  volcanic  dikes. — After  these  remarks  on  the  form 


Fig.  630. 


480  ROCKS  ALTERED  BY  TRAP  DIKES.  [Cii.  XXIX 

and  composition  of  dikes  themselves,  I  shall  describe  the  alterations  which 
they  sometimes  produce  in  the  rocks  in  contact  with  them.  The  changes 
are  usually  such  as  the  intense  heat  of  melted  matter  and  the  entangled 
gases  might  be  expected  to  cause. 

Plas-Newydd. — A  striking  example,  near  Plas-Newydd,  in  Anglesea, 
has  been  described  by  Professor  Henslow.*  The  dike  is  134  feet  wide, 
and  consists  of  a  rock  which  is  a  compound  of  felspar  and  augite  (do- 
lerite  of  some  authors).  Strata  of  shale  and  argillaceous  limestone, 
through  which  it  cuts  perpendicularly,  are  altered  to  a  distance  of  30,  or 
even,  in  some  places,  to  35  feet  from  the  edge,  of  the  dike.  The  shale, 
as  it  approaches  the  trap,  becomes  gradually  more  compact,  and  is  most 
indurated  .where  nearest  the  junction.  Here  it  loses  part  of  its  schistose 
structure,  but  the  separation  into  parallel  layers  is  still  discernible.  In 
several  places  the  shale  is  converted  into  hard  porcellanous  jasper.  In 
the  most  hardened  part  of  the  mass  the  fossil  shells,  principally  Producti, 
are  nearly  obliterated  ;  yet  even  here  their  impressions  may  frequently  be 
traced.  The  argillaceous  limestone  undergoes  analogous  mutations, 
losing  its  earthy  texture  as  it  approaches  the  dike,  and  becoming  granular 
and  crystalline.  But  the  most  extraordinary  phenomenon  is  the  appear- 
ance in  the  shale  of  numerous  crystals  of  analcime  and  garnet,  which  are 
distinctly  confined  to  those  portions  of  the  rock  affected  by  the  dike.f 
Some  garnets  contain  as  much  as  20  per  cent,  of  lime,  which  they  may 
have  derived  from  the  decomposition  of  the  fossil  shells  or  Product] . 
The  same  mineral  has  been  observed,  under  very  analogous  circumstances, 
in  High  Teesdale,  by  Professor  Sedgwick,  where  it  also  occurs  in  shale 
and  limestone,  altered  by  basalt.J 

Antrim. — In  several  parts  of  the  county  of  Antrim,  in  the  north  of 
Ireland,  chalk  with  flints  is  traversed  by  basaltic  dikes.  The  chalk  is 
there  converted  into  granular  marble  near  the  basalt,  the  change  some- 
times extending  8  or  10  feet  from  the  wall  of  the  dike,  being  greatest 
near  the  point  of  contact,  and  thence  gradually  decreasing  till  it  becomes 
evanescent.  "  The  extreme  effect,"  says  Dr.  Berger,  "  presents  a  dark 
brown  crystalline  limestone,  the  crystals  running  in  flakes  as  large  as 
those  of  coarse  primitive  (metamorphic)  limestone ;  the  next  state  is 
saccharine,  then  fine-grained  and  arenaceous  ;  a  compact  variety,  having 
a  porcellanous  aspect  and  a  bluish-gray  color,  succeeds  :  this,  towards  the 
outer  edge,  becomes  yellowish-white,  and  insensibly  graduates  into  the 
unaltered  chalk.  The  flints  in  the  altered  chalk  usually  assume  a  gray 
yellowish  color."§  All  traces  of  organic  remains  are  effaced  in  that  part 
of  the  limestone  which  -is  most  crystalline. 

The  annexed  drawing  (fig.  631)  represents  three  basaltic  dikes  tra- 
versing the  chalk,  all  within  the  distance  of  90  feet.  The  chalk  contigu- 
ous to  the  two  outer  dikes  is  converted  into  a  finely  granular  marble,  m  m, 
as  are  the  whole  of  the  masses  between  the  outer  dikes  and  the  central 

*  Cambridge  Transactions,  vol.  i.  p.  402,  f  Ibid.  vol.  i.  p.  410. 

t  Ibid.  vol.  ii.  p.  175. 

§  Dr.  Berger  Geol.  Trans.  1st  scries,  vol.  iii.  p.  172. 


CH.  XXIX.]  ROCKS  ALTERED  BY  TRAP  DIKES. 

Fig.  681. 


481 


Basaltic  dikes  in  chalk  in  island  of  Eathlin,  Antrim. 
Ground  plan,  as  seen  on  the  beach.    (Conybeare  and  Buckland.*) 

one.  The  entire  contrast  in  the  composition  and  color  of  the  intrusive 
and  invaded  rocks,  in  these  cases,  renders  the  phenomena  peculiarly  clear 
and  interesting. 

Another  of  the  dikes  of  the  northeast  of  Ireland  has  converted  a  mass 
of  red  sandstone  into  hornstone.  By  another,  the  shale  of  the  coal-meas- 
ures has  been  indurated,  assuming  the  character  of  flinty  slate  ;  and  in 
another  place  the  slate-clay  of  the  Lias  has  been  changed  into  flinty 
slate,  which  still  retains  numerous  impressions  of  ammonites. f 

It  might  have  been  anticipated  that  beds  of  coal  would,  from  their 
combustible  nature,  be  affected  in  an  extraordinary  degree  by  the  contact 
of  melted  rock.  Accordingly,  one  of  the  greenstone  dikes  of  Antrim,  on 
passing  through  a  bed  of  coal,  reduces  it  to  a  cinder  for  the  space  of 
9  feet  on  each  side. 

At  Cockfield  Fell,  in  the  north  of  England,  a  similar  change  is  observed. 
Specimens  taken  at  the  distance  of  about  30  yards  from  the  trap  are  not 
distinguishable  from  ordinary  pit-coal ;  those  nearer  the  dike  are  like  cin- 
ders, and  have  all  the  character  of  coke  ;  while  those  close  to  it  are  con- 
verted into  a  substance  resembling  soot.| 

As  examples  might  be  multiplied  without  end,  I  shall  merely  select 
one  or  two  others,  and  then  conclude.  The  rock  of  Stirling  Castle  is  a 
calcareous  sandstone,  fractured  and  forcibly  displaced  by  a  mass  of  green- 
stone which  has  evidently  invaded  the  strata  in  a  melted  state.  The 
sandstone  has  been  indurated,  and  has  assumed  a  texture  approaching  to 
hornstone  near  the  junction.  In  Arthur's  Seat  and  Salisbury  Crag,  near 
Edinburgh,  a  sandstone  which  comes  in  contact  with  greenstone  is  con- 
verted into  a  jaspideous  rock. 

The  secondary  sandstones  in  Skye  are  converted  into  solid  quartz  in 
several  places,  where  they  come  in  contact  with  veins  or  masses  of  trap ; 
and  a  bed  of  quartz,  says  Dr.  MacCulloch,  found  near  a  mass  of  trap, 
among  the  coal  strata  of  Fife,  was  in  all  probability  a  stratum  of  ordinary 
sandstone,  having  been  subsequently  indurated  and  turned  into  quartzite 
by  the  action  of  heat.§ 

But  although  strata  in  the  neighborhood  of  dikes  are  thus  altered  in 

*  Geol.  Trans.  1st  series,  vol.  iii.  p.  210  and  plate  10. 
|  Ibid.  p.  213  ;  and  Playfair,  Illust.  of  Hutt.  Theory,  s.  253. 
$  Sedgwick,  Camb.  Trans.  voL  il  p.  37. 
§  Syst  of  Geol.  vol.  i.  p.  206. 
31 


INTRUSION  OF  TRAP  BETWEEN  STRATA.      [Cn.  XXIX 

a  variety  of  cases,  shale  being  turned  into  flinty  slate  or  jasper,  limestone 
into  crystalline  marble,  sandstone  into  quartz,  coal  into  coke,  and  the 
fossil  remains  of  all  such  strata  wholly  and  in  part  obliterated,  it  is  by  no 
means  uncommon  to  meet  with  the  same  rocks,  even  in  the  same  dis- 
tricts, absolutely  unchanged  in  the  proximity  of  volcanic  dikes. 

This  great  inequality  in  the  effects  of  the  igneous  rocks  may  often  arise 
from  an  original  difference  in  their  temperature,  and  in  that  of  the  entan- 
gled gases,  such  as  is  ascertained  to  prevail  in  different  lavas,  or  in  the 
same  lava  near  its  source  and  at  a  distance  from  it.  The  power  also  of 
the  invaded  rocks  to  conduct  heat  may  vary,  according  to  their  composi- 
tion, structure,  and  the  fractures  which  they  may  have  experienced,  and 
perhaps,  also,  according  to  the  quantity  of  water  (so  capable  of  being 
heated)  which  they  contain.  It  must  happen  in  some  cases  that  the  com- 
ponent materials  are  mixed  in  such  proportions  as  prepare  them  readily  to 
enter  into  chemical  union,  and  form  new  minerals ;  while  in  other  cases 
the  mass  may  be  more  homogeneous,  or  the  proportions  less  adapted  for 
such  union. 

We  must  also  take  into  consideration,  that  one  fissure  may  be  simply 
filled  with  lava,  which  may  begin  to  cool  from  the  first ;  whereas  in 
other  cases  the  fissure  may  give  passage  to  a  current  of  melted  matter, 
which  may  ascend  for  days  or  months,  feeding  streams  which  are  over- 
flowing the  country  above,  or  are  ejected  in  the  shape  of  scoriae  from 
some  crater.  If  the  walls  of  a  rent,  moreover,  are  heated  by  hot  vapor 
before  the  lava  rises,  as  we  know  may  happen  on  the  flanks  of  a  volcano, 
the  additional  caloric  supplied  by  the  dike  and  its  gases  will  act  more 
powerfully. 

Intrusion  of  trap  between  strata. — In  proof  of  the  mechanical  force 
which  the  fluid  trap  has  sometimes  exerted  on  the  rocks  into  which  it 
has  intruded  itself,  I  may  refer  to  the  Whin-Sill,  where  a  mass  of  basalt, 
from  60  to  80  feet  in  height,  represented  by  a,  fig.  632,  is  in  part 

Fig.  682. 


limestone  and  K~ti(il& 


Trap  interposed  between  displaced  beds  of  limestone  and  shale,  at  White 
Force,  High  Teesdale,  Durham.    (Sedgwick.*) 

wedged  in  between  the  rocks  of  limestone,  £>,  and  shale,  c,  which  have 
been  separated  from  the  great  mass  of  limestone  and  shale,  J,  with  which 
they  were  united. 

*  Camb.  Trans,  vol.  ii.  p.  180. 


CH.  XXIX.]  STKUCTUEE   OF  VOLCANIC  EOCKS.  483 

• 

The  shale  in  this  place  is  indurated ;  and  the  limestone,  which  at  a 
distance  from  the  trap  is  blue,  and  contains  fossil  corals,  is  here  converted 
into  granular  marble  without  fossils. 

Masses  of  trap  are  not  unfrequently  met  with  intercalated  between 
strata,  and  maintaining  their  parallelism  to  the  planes  of  stratification 
throughout  large  areas.  They  must  in  some  places  have  forced  their 
way  laterally  between  the  divisions  of  the  strata,  a  direction  in  which  there 
would  be  the  least  resistance  to  an  advancing  fluid,  if  no  vertical  rents 
communicated  with  the  surface,  and  a  powerful  hydrostatic  pressure  were 
caused  by  gases  propelling  the  lava  upwards. 

Columnar  and  globular  structure. — One  of  the  characteristic  forms 
of  volcanic  rocks,  especially  of  basalt,  is  the  columnar,  where  large  masses 
are  divided  into  regular  prisms,  sometimes  easily  separable,  but  in  other 
cases  adhering  firmly  together.  The  columns  vary  in  the  number  of 
angles,  from  three  to  twelve  ;  but  they  have  most  commonly  from  five  to 
seven  sides.  They  are  often  divided  transversely,  at  nearly  equal  dis- 
tances, like  the  joints  in  a  vertebral  column,  as  in  the  Giant's  Causeway, 
in  Ireland.  They  vary  exceedingly  in  respect  to  length  and  diameter. 
Dr.  MacCulloch  mentions  some  in  Skye  which  are  about  400  feet  long ; 
others,  in  Morven,  not  exceeding  an  inch.  In  regard  to  diameter,  those 
of  Ailsa  measure  9  feet,  and  those  of  Morven  an  inch  or  less.*  They  are 
usually  straight,  but  sometimes  curved ;  and  examples  of  both  these  occur 
in  the  isknd  of  StafFa.  In  a  horizontal  bed  or  sheet  of  trap  the  columns 
are  vertical ;  in  a  vertical  dike  they  are  horizontal.  Among  other  exam- 
ples of  the  last-mentioned  phenomenon  is  the  mass  of  basalt,  called  the 
Chimney,  in  St.  Helena  (see  fig.  633),  a  pile  of  hexagonal  prisms,  64  feet 


Fig.  634 


Small  portion  of  the  dyke 
in  Fig.  638. 


Yolcanic  dyke  composed  of  hori- 
zontal prisms.    St.  Helena. 


high,  evidently  the  remainder  of  a  narrow  dike,  the  walls  of  rock  which 
the  dike  originally  traversed  having  been  removed  down  to  the  level  of 

*  MacCuL  Sys.  of  GeoL  voL  ii.  p.  137. 


484 


STRUCTURE   OF  VOLCANIC  ROCKS. 


[On.  XXIX. 


the  sea.     In  fig.  634,  a  small  portion  of  this  dike  is  represented  on  a  less 
reduced  scale.* 

It  being  assumed  that  columnar  trap  has  consolidated  from  a  fluid 
state,  the  prisms  are  said  to  be  always  at  right  angles  to  the  cooling  sur- 
faces. If  these  surfaces,  therefore,  instead  of  being  either  perpendicular 
or  horizontal,  are  curved,  the  columns  ought  to  be  inclined  at  every 
angle  to  the  horizon ;  and  there  is  a  beautiful  exemplification  of  this 
phenomenon  in  one  of  the  valleys  of  the  Vivarais,  a  mountainous  district 
in  the  South  of  France,  where,  in  the  midst  of  a  region  of  gneiss,  a 
geologist  encounters  unexpectedly  several  volcanic  cones  of  loose  sand 
and  scorise.  From  the  crater  of  one  of  these  cones,  called  La  Coupe 
d'Ayzac,  a  stream  of  lava  descends  and  occupies  the  bottom  of  a  nar- 
row valley,  except  at  those  points  where  the  river  Volant,  or  the  torrents 
which  join  it,  have  cut  away  portions  of  the  solid  lava.  The  accom- 
panying sketch  (fig.  635)  represents  the  remnant  of  the  lava  at  one  of 

Fig.  635. 


Lava  of  La  Coupe  d'Ayzac,  new-  Autraigue,  in  the  province  of  Ardeche. 

the  points  where  a  lateral  torrent  joins  the  main  valley  of  the  Volant. 
It  is  clear  that  the  lava  once  filled  the  whole  valley  up  to  the  dotted 
line  d  a ;  but  the  river  has  gradually  swept  away  all  below  that  line, 
while  the  tributary  torrent  has  laid  open  a  transverse  section  ;  by  which 
we  perceive,  in  the  first  place,  that  the  lava  is  composed,  as  usual  in  this 
country,  of  three  parts :  the  uppermost,  at  a,  being  scoriaceous ;  the 
second,  6,  presenting  irregular  prisms ;  and  the  third,  c,  with  regular  col- 
umns, which  are  vertical  on  the  banks  of  the  Volant,  where  they  rest  on  a 
horizontal  base  of  gneiss,  but  which  are  inclined  at  an  angle  of  45°  at  ^, 
and  are  horizontal  at/,  their  position  having  been  everywhere  determined, 
according  to  the  law  before  mentioned,  by  the  concave  form  of  the  origi- 
nal valley. 

In  the  annexed  figure  (636)  a  view  is  given  of  some  of  the  inclined  and 
curved  columns  which  present  themselves  on  the  sides  of  the  valleys  in 
the  hilly  region  north  of  Vicenza,  in  Italy,  and  at  the  foot  of  the  higher 
Alps.f  Unlike  those  of  the  Vivarais,  last  mentioned,  the  basalt  of  this 
country  was  evidently  submarine,  and  the  present  valleys  have  since  been 
hollowed  out  by  denudation. 

*  Seale's  Geognosy  of  St.  Helena,  plate  9. 

\  Fortis.  M6m.  sur  1'Hist.  Nat.  de  1'Italie,  torn.  i.  p.  283,  plate  7. 


OIL  XXIX.] 


STRUCTURE   OF   VOLCANIC  ROCKS. 


±85 


The  columnar  structure  is  by  no  means  Fis-  636- 

peculiar  to  the  trap  rocks  in  which  augite 
abounds ;  it  is  also  observed  in  clinkstone, 
tractate,  and  other  felspathic  rocks  of  the 
igneous  class,  although  in  these  it  is  rarely 
exhibited  in  such  regular  polygonal  forms. 

It  has  been  already  stated  that  basaltic 
columns  are  often  divided  by  cross  joints. 
Sometimes  each  segment,  instead  of  an 
angular,  assumes  a  spheroidal  form,  so  that 
a  pillar  is  made  up  of  a  pile  of  balls,  usually 
flattened,  as  in  the  Cheese-grotto  at  Bert- 
rich-Baden,  in  the  Eifel,  near  the  Moselle 
(fig.  637).  The  basalt  there  is  part  of  a 
small  stream  of  lava,  froin  30  to  40  feet  thick,  which  has  proceeded  from 
one  of  several  volcanic  craters,  still  extant,  on  the  neighboring  heights. 

Fig.  637, 


Columnar  basalt  in  tho  Vicentin. 
(F<\rtis.) 


Basaltic  pillars  of  the  Kasegrotte,  Bertrich-Baden,  halfway  between  Troves  and  Coblentz. 
Height  of  grotto,  from  7  to  8  feet 

The  position  of  the  lava  bordering  the  river  in  this  valley  might  be  repre- 
sented by  a  section  like  that  already  given  at  fig.  635,  if  we  merely  sup- 
posed inclined  strata  of  slate  and  the  argillaceous  sandstone  called  grey- 
wacke  to  be  substituted  for  gneiss. 

In  some  masses  of  decomposing  greenstone,  basalt,  and  other  trap  rocks, 
the  globular  structure  is  so  conspicuous  that  the  rock  has  the  appearance 
of  a  heap  of  large  cannon  balls.  According  to  the  theory  of  M.  Delesse, 
the  centre  of  each  spheroid  has  been  a  centre  of  crystallization,  around 
which  the  different  minerals  of  the  rock  arranged  themselves  symmetri- 
cally during  the  process  of  cooling.  But  it  was  also,  he  says,  a  centre  of 
contraction,  produced  by  the  same  cooling.  The  globular  form,  therefore, 
of  such  spheroids  is  the  combined  result  of  crystallization  and  contraction.* 


*  Delesse,  sur  les  Roches  Globuleuses,  Mem.  de  la  Soc.  G6ol.  de  France,  2  ser. 
torn.  iv. 


RELATION"  OF  TRAP, 


[Cn.  XXIX. 


Fig.  638. 


A  striking  example  of  this  structure  occurs  in  a  resinous  trachyte  or 
pitchstone-porphyry  in  one  of  the  Ponza  islands,  which  rise  from  the 
Mediterranean,  off  the  coast  of  Terracina  and  Gaeta.  The  globes  vary 
from  a  few  inches  to  three  feet  in  diameter, 
and  are  of  an  ellipsoidal  form  (see  fig.  638). 
The  whole  rock  is  in  a  state  of  decomposi- 
tion, "  and  when  the  balls,"  says  Mr.  Scrope, 
"have  been  exposed  a  short  time  to  the 
.weather,  they  scale  off  at  a  touch  into  nu- 
merous concentric  coats,  like  those  of  a 
bulbous  root,  inclosing  a  compact  nucleus. 
The  laminae  of  this  nucleus  have  not  been 
so  much  loosened  by  decomposition ;  but 
the  application  of  a  ruder  blow  will  pro- 
duce a  still  further  exfoliation."* 

A  fissile  texture  is  occasionally  assumed 
by  clinkstone  and  other  trap  rocks,  so  that 
they  have  been  used  for  roofing  houses. 
Sometimes  the  prismatic  and  slaty  struc- 
ture is  found  in  the  same  mass.  The  causes 
which  give  rise  to  such  arrangements  are 
very  obscure,  but  are  supposed  to  be  con- 
nected with  changes  of  temperature  during 
the  cooling  of  the  mass,  as  will  be  pointed  out  in  the  sequel.  (See  chaps. 
xxxv.  and  xxxvi.) 


Globiform  pitchstone.     Chiaja  di 
Luna,  Isle  of  Ponza.    (Scrope.) 


Relation  of  Trappean  RocJcs  to  the  products  of  active  Volcanoes. 

When  we  reflect  on  the  changes  above  described  in  the  strata  near 
their  contact  with  trap  dikes,  and  consider  how  complete  is  the  analogy 
or  often  identity  in  composition  and  structure  of  the  rocks  called  trappean 
and  the  lavas  of  active  volcanoes,  it  seems  difficult  at  first  to  understand 
how  so  much  doubt  could  have  prevailed  for  half  a  century  as  to  whether 
trap  was  of  igneous  or  aqueous  origin.  To  a  certain  extent,  however, 
there  was  a  real  distinction  between  the  trappean  formations  and  those 
to  which  the  term  volcanic  was  almost  exclusively  confined.  A  large 
portion  of  the  trappean  rocks  first  studied  in  the  north  of  Germany,  and 
in  Norway,  France,  Scotland,  and  other  countries,  were  such  as  had  been 
formed  entirely  under  water,  or  had  been  injected  into  fissures  and  intruded 
between  strata,  and  which  had  never  flowed  out  in  the  air,  or  over  the 
bottom  of  a  shallow  sea.  When  these  products,  therefore,  of  submarine 
or  subterranean  igneous  action  were  contrasted  with  loose  cones  of  scoriae, 
tuff,  and  lava,  or  with  narrow  streams  of  lava  in  great  part  scoriaceous 
and  porous,  such  as  were  observed  to  have  proceeded  from  Vesuvius  and 
Etna,  the  resemblance  seemed  remote  and  equivocal.  It  was,  in  truth, 

*  Scrope,  Geol.  Trans.  2d  series,  vol.  ii.  p.  205. 


CH.  XXIX.]  LAVA,   AND   SCORLE.  487 

like  comparing  the  roots  of  a  tree  with  its  leaves  and  branches,  which, 
although  they  belong  to  the  same  plant,  differ  in  form,  texture,  color, 
mode  of  growth,  and  position.  The  external  cone,  with  its  loose  ashes 
and  porous  lava,  may  be  likened  to  the  light  foliage  and  branches,  and 
the  rocks  concealed  far  below,  to  the  roots.  But  it  is  not  enough  to  say 
of  the  volcano, 

"  quantum  vertice  in  auras 
^Etherias,  tantum  radice  in  Tartara  tendit," 

for  its  roots  do  literally  reaca  downwards  to  Tartarus,  or  to  the  re- 
gions of  subterranean  fire ;  and  what  is  concealed  far  below  is  probably 
always  more  important  in  volume  and  extent  than  what  is  visible  above 
ground.  •"•• 

We  have  already  stated  how  frequently  dense  masses  of  strata  have 
been  removed  by  denudation  from  wide  areas  (see  chap,  vi.) ;  and  this 
fact  prepares  us  to  expect  a  similar  destruc- 
tion of  whatever  may  once  have  formed  the 
uppermost  part  of  ancient  submarine  or  sub- 
aerial  volcanoes,  more  especially  as  those 
superficial  parts  are  always  of  the  lightest 
and  most  perishable  materials.  The  abrupt 
manner  in  which  dikes  of  trap  usually  ter- 
minate at  the  surface  (see  fig.  639),  and 
the  water-worn  pebbles  of  trap  in  the  allu- 
vium  which  covers  the  dike,  prove  incon- 
testably  that  whatever  was  uppermost  in 
these  formations  has  been  swept  away.  It  is  easy,  therefore,  to  conceive 
that  what  is  gone  in  regions  of  trap  may  have  corresponded  to  what  is 
now  visible  in  active  volcanoes. 

It  will  be  seen  in  the  following  chapters,  that  in  the  earth's  crust 
there  are  volcanic  tuffs  of  all  ages,  containing  marine  shells,  which  bear 
witness  to  eruptions  at  many  successive  geological  periods.  These  tuffs, 
and  the  associated  trappean  rocks,  must  not  be  compared  to  lava 
and  scoriae  which  had  cooled  in  the  open  air.  Their  counterparts  must 
be  sought  in  the  products  of  modern  submarine  volcanic  eruptions. 
If  it  be  objected  that  we  have  no  opportunity  of  studying  these  last, 
it  may  be  answered,  that  subterranean  movements  have  caused,  al- 
most everywhere  in  regions  of  active  volcanoes,  great  changes  in  the 
relative  level  of  land  and  sea,  in  times  comparatively  modern,  so  as 
to  expose  to  view  the  effects  of  volcanic  operations  at  the  bottom  of 
the  sea. 

Thus,  for  example,  the  examination  of  the  igneous  rocks  of  Sicily, 
especially  those  of  the  Val  di  Noto,  has  proved  that  all  the  more  ordi- 
nary varieties  of  European  trap  have  been  there  produced  under  the 
waters  of  the  sea,  at  a  modern  period ;  that  is  to  say,  since  the  Mediter- 
ranean has  been  inhabited  by  a  great  proportion  of  the  existing  species  of 
testacea. 


488  KELATION  OF  TRAP,  [Cn.  XXIX 

These  igneous  rocks  of  the  Yal  di  Noto,  and  the  more  ancient  trappear. 
rocks  of  Scotland  and  other  countries,  differ  from  subaerial  volcanic  for- 
mations in  being  more  compact  and  heavy,  and  in  forming  sometimes 
extensive  sheets  of  matter  intercalated  between  marine  strata,  and  some- 
times stratified  conglomerates,  of  which  the  rounded  pebbles  are  all  trap. 
They  differ  also  in  the  absence  of  regular  cones  and  craters,  and  in  the 
want  of  conformity  of  the  lava  to  the  lowest  levels  of  existing  valleys. 

It  is  highly  probable,  however,  that  insular  cones  did  exist  in  some 
parts  of  the  Yal  di  Noto ;  and  that  they  were  removed  by  the  waves, 
in  the  same  manner  as  the  cone  of  Graham  Island,  in  the  Mediterra- 
nean, was  swept  away  in  1831,  and  that  of  Nyoe,  off  Iceland,-  in 
1783.*  All  that  would  remain  in  such  cases,  after  the  bed  of  the 
sea  has  been  upheaved  and  laid  dry,  would  be  dikes  and  shapeless 
masses  of  igneous  rock,  cutting  through  sheets  of  lava  which  may  have 
spread  over  the  level  bottom  of  the  sea,  and  strata  of  tuff",  formed  of  ma- 
terials first  scattered  far  and  wide  by  the  winds  and  waves,  and  then  de- 
posited. Conglomerates  also,  with  pebbles  of  trap,  to  which  the  action 
of  the  waves  must  give  rise  during  the  denudation  of  such  volcanic 
islands,  will  emerge  from  the  deep  whenever  the  bottom  of  the  sea  be- 
comes land.  The  proportion  of  volcanic  matter  which  is  originally  sub- 
marine must  always  be  very  great,  as  those  volcanic  vents  which  are  not 
entirely  beneath  the  sea  are  almost  all  of  them  in  islands,  or,  if  on  conti- 
nents, near  the  shore. 

As  to  the  absence  of  porosity  in  the  trappean  formations,  the  appear- 
ances are  in  a  great  degree  deceptive,  for  all  amygdaloids  are,  as  already 
explained,  porous  rocks,  into  the  cells  of  which  mineral  matter  such  as 
silex,  carbonate  of  lime,  and  other  ingredients  have  been  subsequently 
introduced  (see  p.  469) ;  sometimes,  perhaps,  by  secretion  during  the 
cooling  and  consolidation  of  lavas. 

In  the  Little  Cumbray,  one  of  the  Western  Islands,  near  Arran,  the 
amygdaloid  sometimes  contains  elongated  cavities  filled  with  brown  spar ; 
and  when  the  nodules  have  been  washed  out,  the  interior  of  the  cavities 
is  glazed  with  the  vitreous  varnish  so  characteristic  of  the  pores  of 
slaggy  lavas.  Even  in  some  parts  of  this  rock  which  are  excluded  from 
air  and  water,  the  cells  are  empty,  and  seem  to  have  always  remained 
in  this  state,  and  are  therefore  undistinguishable  from  some  modern 
lavas.f 

Dr.  MacCulloch,  after  examining  with  great  attention  these  and 
the  other  igneous  rocks  of  Scotland,  observes,  "  that  it  is  a  mere. 
dispute  about  terms,  to  refuse  to  the  ancient  eruptions  of  trap  the 
name  of  submarine  volcanoes ;  for  they  are  such  in  every  essential 
point,  although  they  no  longer  eject  fire  and  smoke."  J  The  same 
author  also  considers  it  not  improbable  that  some  of  the  volcanic 

*  See  Princ.  of  Geol.,  Index,  "  Graham  Island,"  "Fyoe,"  "Conglomerates,  vol- 
canic," &c. 

f  MacCulloch,  West  Islands,  voL  iL  p.  487. 
i  Syst  of  Geol.  vol.  ii.  p.  114. 


CH.  XXIX.]  LAVA,  AND   SCORIAE.  489 

rocks  of  the  same  country  may  have  been  poured  out  in  the  open 
air.* 

Although  the  principal  component  minerals  of  subaerial  lavas  are  the 
same  as  those  of  intrusive  trap,  and  both  the  columnar  and  globular 
structure  are  common  to  both,  there  are,  nevertheless,  some  volcanic 
rocks  which  never  occur  in  currents  of  lava,  such  as  greenstone,  the 
more  crystalline  porphyries,  and  those  traps  in  which  quartz  and  mica 
appear  as  constituent  parts.  In  short,  the  intrusive  trap  rocks,  forming 
the  intermediate  step  between  lava  and  the  plutonic  rocks,  depart  in 
their  characters  from  lava  in  proportion  as  they  approximate  to  granite. 

These  views  respecting  the  relations  of  the  volcanic  and  trap  rocks  will 
be  better  understood  when  the  reader  has  studied,  in  the  33d  chapter, 
what  is  said  of  the  plutonic  formations. 

EXTERNAL  FORM,  STRUCTURE,  AND  ORIGIN  OF  VOLCANIC  MOUNTAINS. 

The  origin  of  volcanic  cones  with  crater-shaped  summits  has  been  allu- 
ded to  in  the  last  chapter  (p.  462),  and  more  fully  explained  in  the 
"  Principles  of  Geology"  (chaps,  xxiv.  to  xxvii.),  where  Vesuvius,  Etna, 
Santorin,  and  Barren  Island  are  described.  The  more  ancient  portions  of 
those  mountains  or  islands,  formed  long  before  the  times  of  history,  ex- 
hibit the  same  external  features  and  internal  structure  which  belong  to 
most  of  the  extinct  volcanoes  of  still  higher  antiquity  ;  and  these  last  have 
evidently  been  due  to  a  complicated  series  of  operations,  varied  in  kind 
according  to  circumstances :  as,  for  example,  whether  the  accumulation 
took  place  above  or  below  the  level  of  the  sea  ;  whether  the  lava  issued 
from  one  or  several  contiguous  vents.;  and,  lastly,  whether  the  rocks  re- 
duced to  fusion  in  the  subterranean  regions  happen  to  have  contained 
more  or  less  silica,  potash,  soda,  lime,  iron,  and  other  ingredients. 

"We  are  best  acquainted  with  the  effects  of  eruptions  above  water,  or 
those  called  subaerial  or  supramarine  ;  yet  the  products  even  of  these  are 
arranged  in  so  many  ways  that  their  interpretation  has  given  rise  to  a 
variety  of  contradictory  opinions,  some  of  which  will  have  to  be  con- 
sidered in  this  chapter. 

Craters  and  Calderas,  Sandioich  Islands. — We  learn  from  Mr.  Dana's 
valuable  work  on  the  geology  of  the  United  States'  Exploring  Expedition, 
published  in  1849,  that  two  of  the  principal  volcanoes  of  the  Sandwich 
Islands,  Mounts  Loa  and  Kea  in  Owyhee,  are  huge  flattened  volcanic 
cones,  about  14,000  feet  high  (see  fig.  640),  each  equalling  two  and  a  half 
Etnas  in  their  dimensions. 

From  the  summits  of  these  lofty  though  featureless  hills,  and  from 
vents  not  far  below  their  summits,  successive  streams  of  lava,  often 
2  miles  or  more  in  width,  and  sometimes  26  miles  long,  have  flowed. 
They  have  been  poured  out  one  after  the  other,  some  of  them  in  recent 
times,  in  every  direction  from  the  apex  to  the  cone,  down  slopes  varying 

*  Syst.  of  Geol.  voL  ii.  p.  114. 


490          EXTERNAL  FORM,   STRUCTURE,  AND  'ORIGIN     [On.  XXIX, 

Fig.  640. 


Mount  Loa,  in  the  Sandwich  Islands.    (Dana.) 

a.  Crater  at  the  summit.  &.  The  lateral  crater  of  Kilauea. 

The  dotted  lines  indicate  a  supposed  column  of  solid  rock  caused  by  the  lava  consolidating  after 

eruptions. 

on  an  average  from  4  degrees  to  8  degrees ;  but  in  some  places  consider- 
ably steeper.  Sometimes  deep  rents  are  formed  on  the  sides  of  these 
conical  mountains,  which  are  afterwards  filled  from  above  by  streams  of 
lava  passing  over  them,  the  liquid  matter  in  such  cases  consolidating  in 
the  fissures  and  forming  dikes. 

The  lateral  crater  of  Kilauea,  6,  fig.  640,  is  3970  feet  above  the  level 
of  the  sea,  or  about  the  same  height  as  Vesuvius.  It  is  an  immense 
chasm,  1000  feet  deep,  and  its  outer  circuit  no  less  than  from  two  to 
three  miles  in  diameter.  Lava  is  usually  seen  to  boil  up  at  the  bottom 
in  a  lake,  the  level  of  which  alters  continually,  for  the  liquid  rises  and 
falls  several  hundred  feet,  according  to  the  active  or  quiescent  state  of  the 
volcano.  But  instead  of  overflowing  the  rim  of  the  crater,  as  commonly 
happens  in  other  vents,  the  column  of  melted  rock,  when  its  pressure 
becomes  excessive,  forces  a  passage  through  some  subterranean  galleries 
or  rents  leading  towards  the  sea.  Mr.  Coan,  an  American  missionary, 
has  described  an  eruption  which  took  place  in  June,  1840,  when  the  lava 
which  had  risen  high  in  the  great  chasm  began  to  escape  from  it.  Its 
direction  was  first  recognized  by  the  emission  of  a  vivid  light  from  the 
bottom  of  an  ancient  crater,  called  Arare,  400  feet  deep  and  6  miles  to 
the  eastward  of  Kilauea.  The  connection  of  this  light  with  the  discharge 
or  tapping  of  the  great  reservoir  was  proved  by  a  change  in  the  level  of 
the  lava  in  Kilauea,  which  sank  gradually  for  three  weeks,  or  until  the 
eruption  ceased,  when  the  lake  stood  400  feet  lower  than  at  the  com- 
mencement of  the  outbreak.  The  passage,  therefore,  of  the  fluid  matter 
from  Kilauea  to  Arare  was  underground,  and  it  is  supposed  by  Mr.  Coan 
to  have  been  at  its  first  outflow  1000  feet  deep  below  the  surface.  The 
next  indication  of  the  subterranean  progress  of  the  same  lava  was 
observed  a  mile  or  two  from  Arare,  where  the  fiery  flood  broke  out  and 
spread  itself  superficially  over  50  acres  of  land,  and  then  again  found  its 
way  underground  for  several  miles  farther  towards  the  sea,  to  reappear 
at  the  bottom  of  a  second  ancient  and  wooded  crater,  which  it  partly 
filled  up.  The  course  of  the  fluid  then  became  again  invisible  for  several 
miles,  until  it  broke  out  for  the  last  time  at  a  point  ascertained  by 
Captain  Wilkes  to  be  1244  feet  above  the  sea,  and  27  miles  distant 
from  Kilauea,  From  thence  it  poured  along  for  12  miles  in  the 
open  air,  and  then  leapt  over  a  cliff  50  feet  high,  and  ran  for  three 
weeks  into  the  sea.  Its  termination  was  at  a  place  about  40  miles 
distant  from  Kilauea.  The  crust  of  the  earth  overlying  the  subterranean 
course  of  the  lava  was  often  traversed  by  innumerable  fissures,  which 
emitted  steam,  and  in  some  places  the  incumbent  rocks  were  uplifted 
20  or  30  feet. 


CH.  XXIX.]  OF  VOLCANIC   MOUNTAINS.  491 

Thus  in  the  same  volcano  examples  are  afforded  of  the  overflowing  of 
lava  from  the  summit  of  a  cone  2|  miles  high,  and  of  the  underflowing  ot 
melted  matter.  Whether  this  last  has  formed  sheets  intercalated  between 
the  stratified  products  of  previous  eruptions,  or  whether  it  has  penetrated 
through  oblique  or  vertical  fissures,  cannot  be  determined.  In  one  in- 
stance, however,  for  a  certain  space,  it  is  said  to  have  spread  laterally, 
uplifting  the  incumbent  soil. 

The  annexed  section  of  the  crater  of  Kilauea,  as  given  by  Mr.  Dana, 
follows  the  line  of  its  shorter  diameter,  a,  6,  which  is  about  7500  feet 


Fig.  641. 


b 


Section  of  the  crater  of  Kilauea  in  the  Sandwich  Islands.    (Dana.) 
a,  &.  External  boundaries  of  the  chasm  in  the  line  of  its  shortest  diameter, 
c,  <?,/,  d.  Black  ledge.  g,  A.  Lake  of  lava. 

long.  The  boundary  cliffs,  a,  c  and  6,  rf,  are  for  the  most  part  quite 
vertical  and  650  feet  high.  They  are  composed  of  compact  rock  in 
layers,  not  divided  by  scoriaB,  some  a  few  inches,  others  30  feet  in 
thickness,  and  nearly  horizontal.  Below  this,  we  come  to  what  is 
called  the  "  black  ledge,"  c,  e  and  /,  c?,  composed  of  similar  stratified 
materials.  This  ledge  is  342  feet  in  height  above  the  lake  of  lava,  <7,  A, 
which  it  encircles.  The  chasm,  a,  6,  and  its  walls  have  probably  been 
due  to  a  former  sinking  down  of  the  incumbent  rocks,  undermined  for 
a  space  by  the  fusion  of  their  foundations.  The  lower  ledge,  c,  e  and 
/,  d,  may  consist  in  part  of  the  mass  which  sank  vertically,  but 
part  of  it  at  least  must  be  made  up  of  layers  of  lava,  which  have  been 
seen  to  pour  one  after  the  other  over  the  "  black  ledge."  If  at  any 
future  period  the  heated  fluid,  ascending  from  the  volcanic  focus  to 
the  bottom  of  the  great  chasm,  should  augment  in  volume,  and,  before 
it  can  obtain  relief,  should  spread  itself  subterraneously,  it  may  melt 
still  farther  the  subjacent  masses,  and,  causing  a  failure  of  support, 
may  enlarge  still  more  the  limits  of  the  amphitheatre  of  Kilauea. 
There  are  distinct  signs  of  subsidences,  from  100  to  200  feet  perpen- 
dicular, which  have  occurred  in  the  neighborhood  of  Kilauea  at  various 
points,  and  they  are  each  bounded  by  vertical  walls.  If  all  of  them  were 
united,  they  would  constitute  a  sunken  area  equal  to  eight  square 
miles,  or  twice  the  extent  of  Kilauea  itself.  Similar  accidents  are  also 
likely  to  occur  near  the  summit  of  a  dome  like  Mount  Loa,  for  the 
hydrostatic  pressure  of  the  lava,  after  it  has  risen  to  the  edge  or  lip 
of  the  highest  crater,  a,  fig.  640,  must  be  great  and  must  create  a  ten- 
dency to  lateral  fissuring,  in  which  case  lava  will  be  injected  into  every 
opening,  and  may  begin  to  undermine.  If,  then,  .some  of  the  melted 
matter  be  drawn  off  by  escaping  at  a  lower  level,  where  the  pressure 


492  ISLAND   OF  JAVA.  [Cu.  XXIX. 

would  be  still  greater,  the  whole  top  of  the  mountain,  or  a  large  part  of 
it,  might  fall  in. 

Instances  of  such  truncations,  however  caused,  have  occurred  in  Java 
and  in  the  Andes  within  the  times  of  history,  and  to  such  events  we  may 
perhaps  refer  a  very  common  feature  in  the  configuration  of  volcanic 
mountains, — namely,  that  the  present  active  cone  of  eruption  is  sur- 
rounded by  the  ruins  of  a  larger  and  older  cone,  usually  presenting  a 
crescent-shaped  precipice  towards  the  newer  cone.  In  volcanoes  long  since 
extinct,  the  erosive  power  of  running  water,  or,  in  certain  cases,  of  the 
sea,  may  have  greatly  modified  the  shape  of  the  "  atrium,"  or  space  be- 
tween the  older  and  newer  cone,  and  the  cavity  may  thereby  be  pro- 
longed downwards,  and  end  in  a  ravine.  In  such  cases  it  may  be  impos- 
sible to  determine  how  much  of  the  missing  rocks  has  been  removed  by 
explosion  at  the  time  when  the  original  crater  was  active,  or  how  much 
by  subsequent  engulfment  and  denudation. 

Java. — One  of  the  latest  contributions  to  cjr  knowledge  of  volcanoes 
will  be  found  in  Dr.  Junghuhn's  work  on  Java,  where  forty-six  conical 
eminences  of  volcanic  origin,  varying  in  elevation  from  4000  to  nearly 
12,000  feet  above  the  sea,  constitute  the  highest  peaks  of  a  mountain 
range,  running  through  the  island  from  east  to  west.  All  of  them, 
with  one  exception,  did  this  indefatigable  traveller  survey  and  map.  In 
none  of  them  could  he  discover  any  marine  remains,  whether  adhering  to 
their  flanks  or  entering  into  their  internal  structure,  although  strata 
of  marine  origin  are  met  with  nearer  the  sea  at  lower  levels.  Dr. 
Junghuhn  ascribes  the  origin  of  each  volcano  to  a  succession  of  sub- 
aerial  eruptions  from  one  or  more  central  vents,  whence  scoriae,  pumice, 
and  fragments  of  rock  were  thrown  out,  and  whence  have  flowed  streams 
of  trachytic  or  basaltic  lava.  Such  overflowings  have  been  witnessed  in 
modern  times  from  the  highest  summits  of  several  of  the  peaks.  The 
external  slope  of  each  cone  is  generally  greatest  near  its  apex,  where 
the  volcanic  strata  have  also  the  steepest  dip,  sometimes  attaining 
angles  of  20,  30,  and  35  degrees,  but  becoming  less  and  less  inclined 
as  they  recede  from  the  summit,  until,  near  their  base,  the  dip  is  re- 
duced to  10  and  often  4  or  5  degrees.*  The  interference  of  the  lavas 
of  adjoining  volcanoes  sometimes  produces  elevated  platforms,  or  "  sad- 
dles," in  which  the  layers  of  rock  may  be  very  slightly  inclined.  At 
the  top  of  many  of  the  loftiest  mountains  the  active  cone  and  crater 
are  of  small  size,  and  surrounded  by  a  plain  of  ashes  and  sand,  this 
plain  being  encircled  in  its  turn  by  what  Dr.  Junghuhn  calls  "  the 
old  crater-wall,"  which  is  often  1000  feet  and  more  in  vertical  height. 
There  is  sometimes  a  terrace  of  intermediate  height  (as  in  the  moun- 
tain called  Tengger),  comparable  to  the  "  black  ledge"  of  Kilauea  (fig. 
641).  Most  of  the  spaces  thus  bounded  by  semicircular  or  more 
than  semicircular  ranges  of  cliffs  are  vastly  superior  in  dimensions  to 

*  Java,  deszelfs  gedaante,  hekleeding  en  invendige  structuur,  door  F.  Jung- 
htihn.  (German  translation  of  2d  edit,  by  Hasskarl,  Leipzic,  1852.) 


CH.  XXIX.]  JAVANESE  CALDERAS.  493 

the  area  of  any  known  crater  or  hollow  which  has  been  observed  in  any 
part  of  the  world  to  be  occupied  by  a  lake  of  liquid  lava.  As  the  Span- 
iards have  given  to  such  large  cavities  the  name  of  Caldera  (or  cauldron), 
it  may  be  useful  to  use  this  term  in  a -technical  sense,  whatever  views  we 
may  entertain  as  to  their  origin.  Many  of  them  in  Java  are  no  less  than 
four  geographical  miles  in  diameter,  and  they  are  attributed  by  Junghuhn 
to  the  truncation  by  explosion  and  subsidence  of  ancient  cones  of  eruption. 
Unfortunately,  although  several  lofty  cones  have  lost  a  portion  of  their 
height  within  the  memory  of  man,  neither  the  inhabitants  of  Java  nor 
their  Dutch  rulers  have  transmitted  to  us  any  reliable  accounts  of  the 
order  of  events  which  occurred.* 

Dr.  Junghuhn  believes  that  Papandayang  lost  some  portion  of  its  sum- 
mit in  1772  ;  but  affirms  that  most  of  the  towns  on  its  sides  said  to  have 
been  engulfed  were  in  reality  overflowed  by  lava. 

From  the  highest  parts  of  many  Javanese  calderas  rivers  flow,  which 
in  the  course  of  ages  have  cut  out  deep  valleys  in  the  mountain's  side. 
As  a  general  rule,  the  outer  slopes  of  each  cone  are  furrowed  by  straight 
and  narrow  ravines  from  200  to  600  feet  deep,  radiating  in  all  directions 
from  the  top,  and  increasing  in  number  as  we  descend  to  lower  zones. 
The  ridges  or  "  ribs,"  intervening  between  these  furrows,  are  very  con- 
spicuous, and  compared  to  the  spokes  of  an  umbrella.  In  a  mountain 
above  10,000  feet  high,  no  furrows  or  intervening  ribs  are  met  with  in 
the  upper  300  or  400  feet.  At  the  height  of  10,000  feet  there  may  be 
no  more  than  10  in  number,  whereas  500  feet  lower  32  of  them  may  be 
counted.  They  are  all  ascribed  to  the  action  of  running  water ;  and  if 
they  ever  cut  through  the  rim  of  a  caldera,  it  is  only  betause  the  cone 
has  been  truncated  so  low  down  as  to  cause  the  summit  to  intersect  a 
middle  region,  where  the  torrents  once  exerted  sufficient  power  to  cause 
a  series  of  such  indentations.  It  appears  from  such  facts,  that,  if  a  cone 
escapes  destruction  by  explosion  or  engulfment,  it  may  remain  uninjured 
in  its  upper  portion,  while  there  is  time  for  the  excavation  of  deep  ravines 
by  lateral  torrents. 

It  is  remarked  by  Dr.  Junghuhn,  as  also  by  Mr.  Dana  in  regard  to  the 
Pacific  Islands,  that  volcanic  mountains,  however  large  and  however  much 
exposed  to  heavy  falls  of  rain,  support  no  rivers  so  long  as  they  are  in  the 
process  of  growth,  or  while  the  highest  crater  emits  from  time  to  time 
showers  of  scoriae  and  floods  of  lava.  Such  ejectamenta  and  such  currents 
of  melted  rock  fill  up  each  superficial  inequality  or  depression  where 
water  might  otherwise  collect,  and  are  moreover  so  porous  that  no  rill  of 
water,  however  small,  can  be  generated.  But  where  the  subterranean  fires 
have  been  long  since  spent,  or  are  nearly  exhausted,  and  where  the  super- 
ficial scoriae  and  lavas  decompose  and  become  covered  with  clayey  soils, 
the  erosive  action  of  water  begins  to  operate  with  a  prodigious  force, 
proportionate  to  the  steepness  of  the  declivities  and  the  incoherent  nature 
of  the  sand  and  ashes.  Even  the  more  solid  lavas  are  occasionally  cavern 

*  See  Principles  of  GeoL  9th  edit.  p.  493. 


494: 


CANARY  ISLANDS. 


rcn.  xxix. 


Fig.  642. 


ous,  and  almost  always  alternate  with  scoriae  and  perishable  tuffs,  so  as  to 
be  readily  undermined,  and  most  of  them  are  speedily  reduced  to  frag- 
ments of  a  transportable  size  because  they  are  divided  by  vertical  joints 
or  split  into  columns. 

Canary  Islands — Palma. — I  have  enlarged  so  fully  in  the  "  Principles 
of  Geology"  on  the  different  views  entertained  by  eminent  authorities 
respecting  the  origin  of  volcanic  cones,  and  the  laws  governing  the  flow 
of  lava,  and  its  consolidation,  that,  in  order  not  to  repeat  here  what  I  have 
elsewhere  published,  I  shall  confine  myself  in  the  remainder  of  this  chap- 
ter to  the  description  of  facts  observed  by  me  during  a  recent  exploration 
of  Madeira  and  some  of  the  Canary  Islands.  In  these  excursions,  made 
in  the  winter  of  1853-4,  I  was  accompanied  by  an  active  fellow-laborer, 
Mr.  Hartung,  of  Konigsberg.  We  visited  among  other  places  the  beau- 
tiful island  of  Palma,  a  spot  rendered  classical  by  the  description  given  of 
it  in  1825  by  the  late  Leopold  Von  Buch,  who  regarded  it  as  a  type  of 
what  he  called  a  "  crater  of  elevation."* 

Palma  is  46  geographical  miles  west  of  TenerifTe.  Seen  from  the  chan- 
nel which  divides  the  two  islands, 
Palma  appears  to  consist  of  two 
principal  mountain  masses,  the  de- 
pression between  them  being  at  a 
(map,  fig.  642),  or  at  the  pass  of 
Tacanda,  which  is  about  4600  feet 
above  the  sea-level.  The  most  nor- 
thern of  these  masses  makes,  not- 
withstanding Certain  irregularities 
hereafter  to  be  mentioned,  a  con- 
siderable approach  in  general  form 
to  a  great  truncated  cone,  having 
in  the  centre  a  huge  and  deep 
cavity  called  by  the  inhabitants 
"La  Caldera."  This  cavity  (6,  c, 
d,  e,  fig.  642)  is  from  3  to  4  geo- 
graphical miles  in  diameter,  and 
the  range  of  precipices  surrounding 
it  vary  from  about  1500  to  2000 
feet  in  vertical  height.  From  their  base  a  steep  slope,  clothed  by  a 
splendid  forest  of  pines,  descends  for  a  thousand  and  sometimes  two  thou- 
sand feet  lower,  the  centre  of  the  Caldera  being  about  2000  feet  above 
the  sea.  The  northern  half  of  the  encircling  ridge  is  more  than  7000 
English  feet  above  the  sea  in  its  highest  peaks,  and  is  annually  white 
with  snow  during  the  winter  months. 

Externally  the  flanks  of  this  truncated  cone  incline  outwards  in  every 
direction,  the  slopes  being  steepest  near  the  crest,  and  lessening  as  they 
approach  the  lower  country.  A  great  number  of  ravines  commence  on 


ff 

=a 

Geogr.  Miles. 


Fuencaliente  Pt. 


Map  of  Palma,  from  Survey  of  Capt.  Vidal,  E.  K 


*  Erhebung's  Crater. 


CH.  XXIX.] 


CALDERA  OF  PALMA. 


495 


the  flanks  of  the  mountain,  a  short  distance  below  the  summit,  shallow 
at  first,  but  getting  deeper  as  they  descend,  and  becoming  at  the  same 
time  more  numerous,  as  in  the  cones  of  Java  before  mentioned. 

So  unbroken  is  the  precipitous  boundary-wall  of  the  Caldera,  except  at 
its  southeastern  end,  where  the  torrent  which  drains  it  through  a  deep 
gorge  (6,  &',  fig.  643),  issues,  there  is  not  even  a  footpath  by  which  one 
can  descend  into  it  save  at  one  place  called  the  Cumbrecito  (e,  map,  fig. 
642,  p.  494).  This  Cumbrecito  is  a  narrow  col  or  watershed  at  the  height 
of  about  2000  feet  above  the  bottom  of  the  Caldera,  and  4000  above  the 
sea,  and  situated  at  the  precise  limit  of  two  geological  formations  presently 
to  be  mentioned.  This  col  also  occurs  at  the  level  where,  in  other  pails 
of  the  Caldera,  the  vertical  precipices  join  the  talus-like,  rocky  slope,  cov- 
ered with  pines.  The  other  or  principal  entrance  by  which  the  Caldera 
is  drained,  is  the  great  ravine  or  barranco,  as  it  is  called  (see  6, &',  fig.  643), 
which  extends  from  the  southwestern  extremity  of  the  Caldera  to  the  sea, 


Fig.  64a 


Map  of  the  Caldera  of  Palma  and  the  great  ravine,  called  "Barranco  de  las  Angustias.'' 
the  Survey  of  Capt  Tidal,  E.  N.,  1S37.    Scale,  two  geographical  miles  to  an  inch. 


From 


496 


ISLAND   OF  PALMA. 


[Cn.  XXIX. 


a  distance  of  4J  geographical  miles,  in  which  space  the  water  of  the  tor- 
rent falls  about  1500  feet. 

Fig.  644. 


View  of  the  Isle  of  Palma,  and  of  the  entrance  into  the  central  cavity  or  Caldera.    From 
Von  Buch's  "  Canary  Islands." 

This  sketch  was  taken  by  Yon  Buch  from  a  point  at  sea  not  visited 
by  us,  but  we  saw  enough  to  convince  us  that  several  lateral  cones  ought 
to  have  been  introduced  on  the  great  slope  to  the  left,  besides  numerous 
deep  furrows  radiating  from  near  the  summit  to  the  sea  (see  the  map, 
fig.  643).  The  sea  does  not  enter  the  great  Barranco,  as  might  be  in- 
ferred from  this  sketch. 

The  annexed  section  (fig.  645)  passes  through  the  island  from  Santa 
Cruz  de  Palma  to  Briera  Point,  or  from  southeast  to  northwest  (see 
map,  p.  494).  It  has  been  drawn  up  on  a  true  scale  of  heights  and 
horizontal  distances  from  the  observations  of  Mr.  Hartung  and  my  own. 


S.P.     a, 


Section  of  the  Island  of  Palma,  from  Point  Briera,  on  the  northwest,  to  Santa  Cruz  de  Palma,  on 
the  southeast    See  map,  fig.  642,  p.  494. 

a,  &.  The  Caldera  (height  of  a,  6000  feet).  c.  Commencement  of  steeper  dip. 

d.  Santa  Cruz  de  Palma  or  Tedote. 

e.  Lateral  cone,  3940  feet  above  the  sea  (Vidal's  Map). 
/  Briera  Point. 

g.  One  of  several  outliers  of  the  upper  formation  in  centre  of  Caldera. 
8.  P.  Half-buried  cone  and  crater  of  San  Pedro. 


The  lavas  are  seen  to  be  slightly  inclined  near  the  sea  at  Santa  Cruz, 
where  we  observed  them  flowing  round  the  cone  of  San  Pedro,  which 
they  have  more  than  half  buried  without  entering  the  crater.  On  start- 
ing from  the  same  part  of  the  sea-coast,  and  ascending  the  deep  Barranco 
de  la  Madera,  we  saw  just  below  c  the  basaltic  lavas  dipping  at  an  angle 
of  5  degrees,  there  being  no  dikes  in  that  region.  Farther  up,  where  the 
dikes  were  still  scarce,  the  dip  of  the  beds  increases  to  10  and  15  degrees, 
and  they  become  still  steeper  as  they  approach  the  Caldera  at  6,  where 
dikes  abound. 


CH.XXIX.] 


SECTION   OF   ISLAND   OF   PALMA. 


497 


fti 

5 


fi's^   llvj 

is^gslki 
l^lPsi 


32 


'.498  STRUCTURE  AND   ORIGIN   OF  THE  [On.  XXIX 

The  section  (fig.  646)  is  at  right  angles  to  the  preceding,  and  cuts 
through  the  cone  in  the  direction  of  the  great  Barranco,  or  from  north- 
east to  southwest. 

The  lowest  of  the  two  slanting  lines,  m,  f,  descending  from  the  Caldera 
to  the  sea  along  the  bottom  of  the  Barranco,  represents  the  present  bed 
of  the  torrent ;  the  upper  line,  &,  Z,  the  height  at  which  beds  of  gravel, 
elevated  high  above  the  present  river-channel,  are  visible  in  detached 
patches,  shown  by  dotted  spaces  at  &,  and  to  the  southwest  of  it,  on  the 
same  slope.  These,  and  the  continuous  stratified  gravel  and  conglomer- 
ate lower  down  at  I  and  *,  are  newer  than  all  the  volcanic  rocks  seen  in 
this  section. 

The  upper  volcanic  formation,  to  be  described  in  the  sequel,  is  traversed 
by  numerous  dikes,  which  could  not  be  expressed  on  this  small  scale. 
The  vertical  lines  in  the  lower  formation  represent  a  few  of  the  perpen- 
dicular dikes  which  abound  there.  Countless  others,  inclined  and  tor- 
tuous, are  found  penetrating  the  same  rocks.  The  five  outliers  of  some- 
what pyramidal  shape,  at  the  bottom  of  the  Caldera  (on  each  side  of  m), 
agree  in  structure  and  composition  with  the  upper  formation,  and  may 
have  subsided  into  their  present  position,  if  the  Caldera  was  caused  by 
engulfment,  or  may  have  slid  down  in  the  form  of  land-slips,  if  the  cavity 
be  attributed  chiefly  to  aqueous  erosion. 

In  the  description  above  given  of  the  section  (fig.  646),  the  cliffs  which 
wall  in  the  Caldera  are  spoken  of  as  consisting  of  two  formations.  Of  these 
the  uppermost  alone  gives  rise  to  vertical  precipices,  from  the  base  of 
which  the  lower  descends  in  steep  slopes,  which,  although  they  have  the 
external  aspect  of  taluses,  are  not  in  fact  made  up  of  broken  materials,  or 
of  ruins  detached  from  the  higher  rocks,  but  consist  of  rocks  in  place. 
Both  formations  are  of  volcanic  origin,  but  they  differ  in  composition  and 
structure.  In  the  upper,  the  beds  consist  of  agglomerate,  scoriae,  lapilli, 
and  lava,  chiefly  basaltic,  the  whole  dipping  outwards,  as  if  from  the  axis 
of  the  original  cone,  at  right  angles  varying  from  10  to  28  degrees.  The 
solid  lavas  do  not  constitute  more  than  a  fourth  of  the  entire  mass,  and 
are  divided  into  beds  of  very  variable  thickness,  some  scoriaceous  and 
vesicular,  others  more  compact,  and  even  in  some  cases  rudely  columnar. 
All  these  more  stony  masses  are  seen  to  thin  out  and  come  to  an  end 
wherever  they  can  be  traced  horizontally  for  a  distance  of  half  or  a  quar- 
ter of  a  mile,  and  usually  sooner.  Coarse  breccias  or  agglomerates  pre- 
dominate in  the  lower  part,  as  if  the  commencement  of  the  second  series 
of  rocks  marked  an  era  of  violent  gaseous  explosions.  Single  beds  of  this 
aggregate  of  angular  stones  and  scoriaB  attain  a  thickness  of  from  200  to 
300  feet.  They  are  united  together  by  a  paste  of  volcanic  dust  or  spongi- 
form  scoriae. 

At  one  point  on  the  right  side  of  the  great  Barranco,  near  its  exit 
from  the  Caldera,  we  observed  in  the  boundary  precipice  a  lofty  column 
of  amorphous  and  scoriaceous  rock  in  which  the  red  or  rust-colored 
scoriae  are  as  twisted  and  ropy  as  any  to  be  seen  on  the  slopes  of 
Vesuvius ;  seeming  to  imply  that  there  was  here  an  ancient  vent  or 


CH.  XXIX.]  CALDEEA  OF    PALMA.  499 

channel  of  discharge  subsequently  buried  under  the  products  of  newer 
eruptions.  Countless  dikes,  more  or  less  vertical,  consisting  chiefly 
of  basaltic  lava,  traverse  the  walls  of  the  Caldera,  some  of  them  ter- 
minating upwards,  but  a  great  number  reaching  the  very  crest  of 
the  ridge,  and  therefore  having  been  posterior  in  origin  to  the  whole 
precipice. 

We  could  not  discover  in  any  one  of  the  fallen  masses  of  agglomerate 
which  strewed  the  base  of  the  cliffs  a  single  pebble  or  waterworn 
fragment.  Each  imbedded  stone  is  either  angular,  or,  if  globular,  consists 
of  scoriae  more  or  less  spongy,  and  evidently  not  owing  its  shape  to  attri- 
tion. It  would  be  impossible  to  account  for  the  absence  of  waterworn 
pebbles  if  the  coarse  breccia  in  question  had  been  spread  by  aqueous 
agency  over  a  horizontal  area  coextensive  with  the  Caldera  and  the  vol- 
canic rocks  which  surround  it.  The  only  cause  known  to  us  capable  of 
dispersing  such  heavy  fragments,  some  of  them  3,  4,  or  6  feet  in  diame- 
ter, without  blunting  their  edges,  is  the  power  of  steam,  unless  indeed  we 
could  suppose  that  ice  had  co-operated  with  water  in  motion ;  and  the 
interference  of  ice  cannot  be  suspected  in  this  latitude  (28°  40'),  espe- 
cially as  I  looked  in  vain  for  signs  of  glacial  action  here  and  in  the  other 
mountainous  regions  of  the  Canary  Islands. 

The  lower  formation  of  the  Caldera  is,  as  before  stated,  equally  of 
igneous  origin.  It  differs  in  its  prevailing  color  from  the  upper,  exhibit- 
ing a  tea-green  and  in  parts  a  light  yellow  tint,  instead  of  the  usual 
brown,  lead-colored,  or  reddish  hues  of  basalt  and  its  associated  scoriae. 
Beds  of  a  light  greenish  tuff  are  common,  together  with  trachytic  and 
greenstone  rocks,  the  whole  so  reticulated  by  dikes,  some  vertical,  others 
oblique,  others  tortuous,  that  we  found  it  impossible  to  determine  the 
general  dip  of  the  beds,  although  at  the  head  of  the  great  gorge  or 
Barranco  they  certainly  dip  outwards,  or  to  the  south,  as  stated  by  Von 
Buch.  But  in  following  the  section  down  the  same  ravine,  where  the 
mountain  called  Alejanado  (c?,  figs.  pp.  494  and  497)  is  cut  through, 
and  where  the  rocks  of  the  lower  formation  are  very  crystalline,  we 
found  what  is  not  alluded  to  by  the  Prussian  geologist,  that  the  beds 
exposed  to  view  in  cliffs  1500  feet  high  have  an  anticlinal  arrange- 
ment, exhibiting  first  a  southerly  and  then  a  northerly  dip  at  angles 
varying  from  20  to  40  degrees  (see  section,  fig.  646  at  &).  Hence 
we  may  presume  that  the  older  strata  must  have  undergone  great 
movements  before  the  upper  formation  was  superimposed.  No  or- 
ganic remains  having  been  discovered  in  the  older  series,  we  cannot 
positively  decide  whether  it  was  of  subaerial  or  submarine  origin. 
We  can  only  affirm  that  it  has  been  produced  by  successive  erup- 
tions, chiefly  of  felspathic  lavas  and  tuffs.  Many  beds  which  probably 
consisted  at  first  of  soft  tuffs  have  been  much  hardened  by  the  contact 
of  dikes  and  apparently  much  altered  by  other  plutonic  influences,  so 
that  they  have  acquired  a  semi-crystalline  and  almost  metamorphic 
character. 

The  existence  of  so  great  a  mass  of  volcanic  rocks  of  ancient  dat6 


500  CALDERA  OF  PALMA.  [Cn.  XXIX 

on  the  exact  site  of  an  equally  vast  accumulation  of  comparatively  mod- 
ern lavas  and  scoriae  is  peculiarly  worthy  of  notice  as  a  general  phenome- 
non observed  in  very  different  parts  of  the  globe.  It  proves  that, 
notwithstanding  the  fact  in  the  past  history  of  volcanoes  that  one  region 
after  another  has  been  for  ages  and  has  then  ceased  to  be  the  chief  theatre 
of  igneous  action,  still  the  activity  of  subterranean  heat  may  often  be  per- 
sistent for  more  than  one  geological  period  in  the  same  place,  relaxing 
perhaps  in  its  energies  for  a  while,  but  then  breaking  out  afresh  with  an 
intensity  as  great  as  ever. 

We  have  still  to  consider  the  mode  of  origin  of  the  higher  volcanic 
mass,  or  the  upper  series  of  rocks  with  which  the  peculiar  form  of  the 
Caldera  is  more  intimately  connected.  The  principal  question  here 
arising  is  this,  whether  the  mass  was  dome-shaped  from  the  beginning, 
having  grown  by  the  superposition  of  one  conical  envelope  of  lava  and 
ashes  formed  over  another,  or  whether,  as  Yon  Buch  and  his  followers 
imagine,  its  component  materials  were  first  spread  out  in  horizontal  or 
nearly  horizontal  deposits,  and  then  upheaved  at  once  into  a  dome-shaped 
mountain  with  a  caldera  in  its  centre.  According  to  the  first  hypothesis 
the  cone  was  built  up  gradually,  and  completed  with  all  its  beds  dipping 
as  now,  and  traversed  by  all  its  dikes,  before  the  Caldera  originated. 
According  to  the  other,  the  Caldera  was  the  result  of  the  same  move- 
ments which  gave  a  dome-shaped  structure  to  the  mass,  and  which 
caused  the  beds  to  be  highly  inclined ;  in  other  words,  the  cone  and 
the  Caldera  were  produced  simultaneously.  So  singularly  opposite  are 
these  views,  that  the  principal  agency  introduced  by  the  one  theory  is 
upheaval,  by  the  other  subsidence.  The  very  name  of  "  Elevation  Cra- 
ters" points  to  the  kind  of  movement  to  which  one  school  attributes  the 
origin  of  a  cone  and  caldera  ;  whereas  the  chief  agencies  appealed  to  by 
the  other  school  are  gaseous  explosions,  engulfment,  and  aqueous  denu- 
dation. 

The  favorable  reception  of  the  doctrine  of  upheaval  has  arisen  from 
the  following  circumstances.  Streams  of  lava,  it  is  said,  which  run  down 
a  declivity  of  more  than  three  degrees  are  never  stony  ;  and,  if  the  slope 
exceed  five  or  six  degrees,  they  are  mere  shallow  and  narrow  strings  of 
vesicular  or  fragmentary  slag.  Whenever,  therefore,  we  find  parallel 
layers  of  stony  lava,  especially  if  they  be  of  some  thickness,  high  up 
in  the  walls  of  a  caldera,  we  may  be  sure  that  they  were  solidified  origi- 
nally on  a  very  gentle  slope ;  and  if  they  are  now  inclined  at  angles 
of  10°,  20°,  or  30°,  not  only  they,  but  all  the  interstratified  beds  of 
lapilli,  scoria3,  tuff,  and  agglomerate,  must  have  been  at  first  nearly  flat, 
and  must  have  been  afterwards  lifted  up  with  the  solid  beds  into 
their  present  position.  It  is  supposed  that  such  a  derangement  of  the 
strata  could  scarcely  fail  to  give  rise  to  a  wide  opening  near  the  centre 
of  upheaval,  and  in  the  case  of  Palma,  the  Caldera  (which  Von  Buch 
called  "the  hollow  axis  of  the  cone")  may  represent  this  breach  of 
continuity. 

Among  other  objections  to  the  elevation-crater  theory  often  advanced 


CH.  XXIX.]  HYPOTHESIS  OF   UPHEAVAL.  '     501 

and  never  yet  answered  are  the  following : — First,  in  most  calderas,  as 
in  Palma,  the  rim  of  the  great  cavity  and  the  circular  range  of  precipices 
surrounding  it  remain  entire  and  unbroken  on  three  sides,  whereas  it  is 
difficult  to  conceive  that  a  series  of  volcanic  strata  2000  or  3000  feet 
thick  could  have  once  extended  over  an  area  six  or  seven  miles  in  its 
shortest  diameter,  and  then  have  been  upraised  bodily,  so  that  the  beds 
should  dip  at  steep  angles  towards  all  points  of  the  compass  from  a  centre, 
and  yet  that  no  great  fractures  should  have  been  produced.  We  should 
expect  to  see  some  open  fissures  on  every  side,  widening  as  they  approach 
the  caldera.  The  dikes,  it  is  true,  do  undoubtedly  attest  many  disloca- 
tions of  the  mass,  which  have  taken  place  at  successive  and  often  distant 
periods.  But  none  of  them  can  have  belonged  to  the  supposed  period  of 
terminal  and  paroxysmal  upheaval,  for,  had  the  caldera  existed  when  they 
originated,  the  melted  matter  now  solidified  in  each  dike  must,  instead  of 
filling  a  rent,  have  flowed  down  into  the  caldera,  tending  sc  ^ar  to  ob- 
literate the  great  cavity. 

The  second  objection  is  the  impossibility  of  imagining  that  so  vast 
a  series  of  agglomerates,  tuffs,  stratified  lapilli,  and  highly  scoriaceous 
lavas  could  have  been  poured  out  within  a  limited  area  without  soon 
giving  rise  to  a  hill,  and  eventually  to  a  lofty  mountain.  Such  heavy 
angular  fragments  as  are  seen  in  the  agglomerates,  single  -beds  of  which 
are  sometimes  200  or  300  feet  thick,  must  when  hurled  into  the  air 
have  fallen  down  again  near  the  vent,  and  would  be  arranged  in  inclined 
layers  dipping  outwards  from  the  central  axis  of  eruption.  It  is  in  per- 
fect accordance  with  this  hypothesis  that  we  should  behold  agglomerates, 
lapilli,  and  scoriae  predominating  in  the  walls  of  the  Caldera ;  whereas 
in  the  ravines  nearer  the  sea,  where  the  inclination  of  the  beds  has  di- 
minished to  10  and  even  to  5  degrees,  the  proportion  of  stony  as  com- 
pared to  fragmentary  materials  is  precisely  reversed.  It  is  also  natural 
that  the  dikes  should  be  most  numerous  where  the  ejectamenta  are  to 
the  more  solid  beds  in  the  proportion  of  3  to  1,  as  at  b,  fig.  645,  p.  496  ; 
while  the  dikes  are  few  in  number  where  the  stony  lavas  predominate 
(as  at  c,  ibid.).  Many  of  the  scoriaceous  beds  at  6  may  be  the  upper 
extremities  of  currents  which  became  stony  and  compact  when  they 
reached  c,  and  flowed  over  a  more  level  country ;  but  this  suggestion 
cannot  be  assented  to  by  the  advocates  of  the  upheaval  theory,  for  it 
assumes  the  existence  of  a  cone  long  before  the  time  had  arrived  for 
the  catastrophe  which  according  to  their  views  gave  rise  to  a  conical 
mountain. 

If,  however,  we  reject  the  doctrine  that  the  beds  were  tilted  by  .a 
movement  posterior  to  the  accumulation  of  all  the  compact  and  frag- 
mentary rocks,  how  are  we  to  account  for  the  steepness  of  the  dip  of 
some  stony  lavas  high  up  in  the  walls  of  the  Caldera  ?  These  masses 
are  occasionally  50  or  100  feet  thick,  of  lenticular  shape,  as  seen  in  the 
cliffs  from  below,  and  to  all  appearance  parallel  to  the  associated  layers 
of  scoriaB  and  lapilli.  But  unfortunately  no  one  can  climb  up  and  de- 
termine how  far  the  supposed  parallelism  may  be  deceptive.  The  solid 


502  STONY  LAVAS  FORMED  ON  SLOPES.  [Cn.  XXIX. 

beds  extend  in  general  over  small  horizontal  spaces,  and  some  of  them 
may  possibly  be  no  other  than  intrusive  lavas,  in  the  nature  of  dikes, 
more  or  less  parallel  to  the  layers  of  ejectamenta.  Such  lavas,  when  the 
crater  was  full,  may  have  forced  their  way  between  highly  inclined  beds 
of  scoriae  and  lapilli.  We  know  that  lava  often  breaks  out  from  the  side 
or  base  of  a  cone,  instead  of  rising  to  the  rim  of  the  crater.  Neverthe- 
less one  or  two  of  the  stony  masses  alluded  to  seemed  to  me  to  resemble 
lavas  which  had  flowed  out  superficially.  They  may  have  solidified  on 
a  broad  ledge  formed  by  the  rim  of  a  crater.  Such  a  rim  might  be  of 
considerable  breadth  after  a  partial  truncation  of  the  cone.  And  some 
lavas  may  now  and  then  have  entirely  filled  up  the  atrium,  or  what  in. 
the  case  of  Somma  and  Vesuvius  is  called  the  atrio  del  cavallo,  that  is 
to  say,  the  interspace  between  the  old  and  new  cone.  When  by  the 
products  of  new  eruptions  a  uniform  slope  has  been  restored,  and  the  two 
cones  have  blended  into  one  (see  e,  d,  c,  fig.  p.  511),  the  next  breaking 
down  of  the  side  of  the  mountain  may  display  a  mass  of  compact  rock  of 
great  thickness  in  the  walls  of  a  caldera,  resting  upon  and  covered  by 
ejectamenta.  Other  extensive  wedges  of  solid  lava  will  be  formed  on  the 
flanks  of  every  volcanic  mountain  by  the  interference  of  lateral,  or,  as 
they  are  often  termed,  parasitic  cones,  which  check  or  stop  the  down- 
ward flow  of  lava,  and  occasionally  offer  deep  craters  into  which  the 
melted  matter  is  poured. 

By  aid  of  one  or  all  the  processes  above  enumerated  we  may  certainly 
explain  a  few  exceptional  cases  of  intercalated  stony  beds,  in  the  midst  of 
others  of  a  loose  and  scoriaceous  nature,  the  whole  being  highly  inclined. 
But  to  account  for  a  succession  of  compact  and  truly  parallel  lavas 
having  a  steep  dip,  we  may  suppose  that  they  flowed  originally  down  the 
flanks  of  a  cone  sloping  at  angles  of  from  4  to  10  degrees,  as  in  many 
active  volcanoes,  and  that  they  acquired  subsequently  a  steeper  inclina- 
tion. It  would  be  rash  to  assume  the  entire  absence  of  local  disturbances 
during  the  growth  of  a  volcanic  mountain.  Some  dikes  are  seen  crossing 
others  of  a  different  composition,  marking  a  distinctness  in  the  periods  of 
their  origin.  The  volume  of  rock  filling  such  a  multitude  of  fissures  as 
we  see  indicated  by  the  dikes  in  Palrna  must  be  enormous ;  so  that, 
could  it  be  withdrawn,  the  mass  of  ejectamenta  would  collapse  and  lose 
both  in  height  and  bulk.  The  injection,  therefore,  of  all  this  matter  in  a 
liquid  state  must  have  been  attended  by  the  gradual  distension  of  the 
cone,  the  increase  of  which  I  have  elsewhere  compared  both  to  the  exo- 
genous and  endogenous  growth  of  a  tree,  as  it  has  been  effected  alike  by 
external  and  internal  accessions. 

*  But  the  acquisition  of  a  steeper  dip  by  such  reiterated  rendings  and 
injections  of  a  cone  is  altogether  opposed  to  the  views  of  those  who 
defend  the  upheaval  hypothesis,  because  it  draws  with  it  the  conclusion 
that  the  slopes  were  always  growing  steeper  and  steeper  in  proportion  as 
the  cone  waxed  older  and  loftier.  Once  admit  this,  and  it  follows,  that  the 
upper  layers  of  solid  lava  must  have  conformed  to  surfaces  already  inclined 
at  angles  of  20,  or,  in  the  case  of  the  Caldera  of  Palma,  28  degrees. 


CH.  XXIX.]  AQUEOUS  EROSION  IX  PALMA.  503 

For  this  reason  the  defenders  of  the  upheaval  hypothesis  are  consistent 
with  themselves  in  assigning  the  whole  movement  by  which  the  strata, 
whether  solid  or  incoherent,  have  been  tilted,  exclusively  to  one  terminal 
catastrophe.  The  whole  development  of  subterranean  force  is  repre- 
sented as  the  last  incident  in  every  series  of  volcanic  operations,  the 
closing  scene  of  the  drama ;  and  the  sudden  and  paroxysmal  nature  of 
the  catastrophe  is  inferred  from  the  absence  of  all  signs  of  successive 
and  intermittent  action  so  characteristic  of  the  antecedent  volcanic  phe- 
nomena. 

I  have  alluded  to  an  opinion  entertained  by  some  able  geologists,  that 
no  lava  can  acquire  any  degree  of  solidity  if  it  flows  down  a  declivity  of 
more  than  three  degrees.  This  doctrine  I  believe  to  be  erroneous.  The 
lava  which  has  flowed  from  the  cone  of  Llarena  near  Port  Orotava,  in 
Tenerifie,  is  very  columnar  in  parts,  and  yet  has  descended  a  slope  of  six 
degrees.  Another  stream  of  recent  aspect  near  the  town  of  El  Passo,  in 
Palma,  has  a  general  inclination  of  ten  degrees,  and  is  remarkable  for 
the  depth  and  extent  of  the  large  basin-shaped  hollows,  20,  30,  and  35 
feet  deep,  seen  everywhere  on  its  surface.  Whenever  another  lava-current 
shall  flow  down  over  this  one,  although  its  average  inclination  will  be  the 
same,  it  must  fill  up  all  these  inequalities,  and  in  doing  so  must  give 
rise  to  masses  of  compact  and  solid  rock  20  or  30  feet  thick,  resting  upon 
and  encircled  by  vesicular  lava.  Other  lavas  northeast  of  Fuencaliente 
at  the  southern  extremity  of  Palma,  so  modem  as  to  be  still  black  and 
uncovered  with  vegetation,  descend  slopes  of  no  less  than  22  degrees,  and 
yet  contain  large  masses  of  compact  stone,  formed  chiefly  on  the  sides  of 
tunnel-shaped  cavities,  15  or  20  feet  deep,  in  which  one  layer  has  solidi- 
fied within  another  on  the  walls  of  these  channels,  while  in  the  central 
part  the  lava  seems  to  have  remained  fluid  so  as  to  run  out  of  the  tunnel, 
leaving  an  arched  cavity,  the  roof  of  which  has  in  most  cases  fallen  in. 
The  strength  of  the  enveloping  crust  of  scoriae  at  the  lower  end  of  a 
lava-current  in  which  one  of  these  tunnels  existed  may  have  been  suf- 
ficient to  arrest  the  progress  of  the  stream  for  hours  or  days,  and  during 
that  time  solidification  may  have  occurred  under  great  hydrostatic 
pressure. 

Before  taking  leave  of  Palma,  we  have  yet  to  consider  another  dis- 
tinct point,  namely,  what  amount  of  denudation  has  taken  place  in 
the  Caldera,  and  its  environs.  Assuming  that  the  great  cavity  or  some 
part  of  it  may  have  originated  in  the  truncation  of  a  cone  in  the  man- 
ner before  suggested,  to  what  extent  has  its  shape  been  subsequently 
enlarged  or  modified  by  aqueous  erosion  ?  It  will  be  remembered  that 
a  conglomerate  of  well-rounded  pebbles,  no  less  than  800  feet  thick, 
was  spoken  of  as  visible  in  the  great  Barranco  (see  description  of  sec- 
tion, pp.  49*7,  498).  That  conspicuous  deposit,  3  or  4  miles  in  length, 
was  evidently  derived  from  the  destruction  of  rocks  like  those  in  the 
Caldera,  for  the  present  torrent  brings  down  annually  similar  stones 
of  every  size,  some  very  large,  and  rounds  them  by  attrition  in  its 
channel.  By  what  changes  in  the  configuration  of  the  island  after 


504:  EXTENT  AND  NATURE  OF        [On.  XXIX. 

the  old  volcano  and  its  Caldera  were  formed  was  so  vast  a  thickness 
of  gravel  formed,  to  be  afterwards  cut  through  to  a  depth  of  800  feet  ? 
The  ravine  through  which  the  torrent  now  flows  has  been  excavated 
to  that  depth  through  the  old  conglomerate.  The  occurrence  of  two  or 
three  layers  of  contemporaneous  lava,  intercalated  between  the  strata  of 
puddingstone,  ought  not  to  surprise  us ;  for  even  in  historical  times 
eruptions  have  been  witnessed  in  the  southern  half  of  Palma.  Such 
basaltic  lavas,  one  of  them  columnar  in  structure,  have  not  come  down 
from  the  Caldera,  but  from  cones  much  nearer  the  sea,  and  immedi- 
ately adjoining  the  Barranco,  like  the  cone  of  Argual  (see  map,  p.  495) 
and  others.  These  lavas,  of  the  same  age  as  the  conglomerate,  consist 
of  three  or  four  currents  of  limited  extent,  for  in  many  parts  of  the  river- 
cliffs  no  volcanic  formation  is  visible  on  either  bank.  On  the  right 
bank  of  the  Barranco,  the  conglomerate,  when  traced  westward,  is  soon 
found  to  come  to  an  end  as  it  abuts  against  the  lofty  precipice  E  (fig.  647), 
which  is  a  prolongation  of  the  western  wall  of  the  Caldera.  Its  extent 
eastward  from  &',  may  be  more  considerable,  but  cannot  be  ascertained, 
as  it  is  concealed  under  modern  scoriae  and  lava  spread  over  the  great 
platform,  F. 

Fig.  64T. 

East 


A.  Ravine  or  Barranco  de  las  Angustias,  near  its  termination  in  Palma. 
Z>,  &',  &".  Conglomerate,  800  feet  thick  in  parts. 

c,  e'.  Lava  intercalated  between  the  beds  of  conglomerate. 

d,  d'.  Another  and  older  current  of  basaltic  lava,  columnar  in  parts. 

E.  Cliff  of  ancient  volcanic  rocks  of  the  Upper  Formation  (p.  500),  a  prolongation  of 

the  western  wall  of  the  Caldera. 

F.  Platform  on  which  the  town  of  Argual  stands. 

As  we  could  find  no  organic  remains  in  the  old  gravel,  we  have  no 
positive  means  of  deciding  whether  it  be  fluviatile  or  marine.  The 
height  of  its  base  above  the  sea,  where  it  is  800  feet  thick,  may  be 
about  350  feet,  but  patches  of  it  ascend  to  elevations  of  1000  and 
1500  feet  near  the  top  of  the  Barranco,  as  shown  at  k,  &c.,  in  section, 
fig.  646,  p.  497.  Such  a  mass  of  gravel,  therefore,  bears  testimony 
to  the  removal  of  a  prodigious  amount  of  materials  from  the  Caldera 
by  the  action  of  water.  Whether  a  river  or  the  sea  was  the  transport- 
ing agent,  it  is  obvious  that  a  large  portion  of  the  volcanic  materials, 
consisting  of  sand,  lapilli,  and  scoriae,  before  described  (p.  498),  as  be- 


CH.  XXIX.]  AQUEOUS  EROSION"  IN  PALMA.  505 

longing  to  the  upper  formation  in  the  Caldera,  would  leave  behind  them 
few  pebbles.  Nearly  all  of  these  perishable  deposits  would  be  swept 
down  in  the  shape  of  mud  into  the  Atlantic.  Even  the  hard  rounded 
stones,  since  they  were  once  angular  and  are  now  ground  down  into  peb- 
bles, must  have  lost  more  than  half  their  original  bulk,  and  bear  witness 
to  large  quantities  of  sedimentary  matter  consigned  to  the  bed  of  the 
ocean.  We  saw  in  the  Caldera  blocks  of  huge  size  thrown  down  by 
cascades  from  the  upper  precipices  during  the  melting  of  the  snows, 
a  fortnight  before  our  visit,  and  much  destruction  was  likewise  going  on 
in  the  lower  set  of  rocks  by  the  same  agency.  We  also  learnt  that 
a  great  flood  rushed  down  the  Barranco  in  the  spring  of  1854,  shortly 
before  our  arrival,  damaging  several  houses  and  farms,  and  I  have  there- 
fore no  doubt  that  the  erosive  power  even  of  rain  and  river  water,  aided 
by  earthquakes,  might  in  the  course  of  ages  empty  out  a  valley  as 
large  as  the  Caldera,  although  probably  not  of  the  same  shape.  I  am 
disposed  to  attribute  the  circular  range  of  cliffs  surrounding  the  Caldera 
to  volcanic  action,  because  they  forcibly  reminded  me  of  the  precipices 
encircling  three  sides  of  the  Val  de  Bove,  on  Etna ;  and  because  they 
agree  so  well  with  Junghuhn's  description  of  the  "old  crater-walls" 
of  active  volcanoes  in  Java,  some  of  which  equal  or  surpass  in  dimen- 
sions even  the  Caldera  of  Palma.  The  latter  may  have  consisted 
at  first  of  a  true  crater,  enlarged  afterwards  into  a  caldera  by  the 
partial  destruction  of  a  great  cone ;  but  if  so,  it  has  certainly  been  since 
modified  by  denudation.  Nor  can  any  geologist  now  define  how  much 
of  the  work  has  been  accomplished  by  aqueous,  and  how  much  by  vol- 
canic agency.  The  phenomenon  of  a  river  cutting  its  channel  through 
a  dense  mass  of  ancient  alluvium  formed  during  oscillations  in  the  level 
of  the  land  is  not  confined  to  volcanic  countries,  and  I  need  not  dwell 
here  on  its  interpretation,  but  refer  to  what  was  said  in  the  7th  chap- 
ter. (See  p.  84.) 

There  remains,  however,  another  question  of  high  theoretical  interest ; 
namely,  whether  the  denudation  was  marine  or  fluviatile.  It  was  stated 
that  the  materials  of  the  great  cone  or  assemblage  of  cones  in  the 
north  of  Palma  are  of  subaerial  origin,  as  proved  by  the  angularity  of 
the  fragments  of  rock  in  the  agglomerates;  but  it  may  be  asked, 
whether,  when  the  Caldera  was  formed  long  afterwards,  it  may  not,  like 
the  crater  of  St.  Paul's  (fig.  649,  p.  509),  have  had  a  communication 
with  the  sea,  which  may  have  entered  by  the  great  Barranco,  and  if, 
after  a  period  of  partial  submergence,  the  island  may  not  then  have  risen 
again  to  its  original  altitude.  In  such  a  case  the  retiring  waters  might 
leave  behind  them  a  conglomerate,  partly  of  river-pebbles,  collected  at 
the  points  where  the  torrent  successively  entered  the  sea,  and  partly 
of  stones  rounded  by  the  waves.  The  torrent  may  have  finally  cut  a 
deep  ravine  in  the  gravel  and  associated  lavas  when  the  land  was  rising 
again.  Such  oscillations  of  level,  amounting  to  more  than  2000  feet, 
would  not  be  deemed  improbable  by  any  geologists,  provided  they 
enable  us  to  explain  more  naturally  than  by  any  other  causation,  the 


506  EXTENT  AXD  NATURE  OF  [Ca  XXTX. 

origin  of  the  physical  outlines  of  the  country.  As  to  the  fact  that  no 
marine  shells  have  yet  been  discovered  in  the  conglomerate,  sufficient 
search  has  not  yet  been  made  for  them  to  entitle  us  to  found  an  argu- 
ment on  such  negative  evidence.  At  the  same  time  I  confess,  that, 
having  found  sea-shells  and  bryozoa  abundantly  in  certain  elevated 
marine,  conglomerates  in  the  Grand  Canary,  before  I  visited  Palma,  and 
being  unable  to  meet  with  any  in  the  Barranco  de  las  Angustias,  I  re- 
garded the  old  gravel  when  I  was  on  the  spot  as  of  fluviatile  origin. 
Such  inferences  are  always  doubtful  in  the  absence  of  more  positive  data, 
and  the  intervention  of  the  sea  will  unquestionably  account  for  some 
phenomena  in  the  configuration  of  the  Caldera  and  Barranco  more 
naturally  than  river  action.  For  example,  we  have  the  lofty  cliff  E,  fig. 
p.  504,  already  mentioned,  and  c,/,  map,  p.  494,  extending  four  or  five 
miles  from  the  Caldera  to  the  sea  on  the  right  bank  of  the  Barrranco, 
and  no  cliff  of  corresponding  height  or  structure  on  the  other  bank, 
where  for  miles  towards  the  southeast  there  is  the  platform  F,  fig.  p.  504, 
supporting  several  minor  volcanic  cones.  The  sea  might  be  supposed  to 
leave  just  such  a  cliff  as  E,  after  cutting  away  a  portion  of  the  southwest- 
ern extremity  of  the  old  dome-shaped  mountain  in  the  north  of  Palma, 
whereas  a  torrent  or  river  would  leave  a  cliff  of  similar  structure  and 
nearly  equal  height  on  both  banks.  As  to  the  fact  of  the  old  con- 
glomerate ascending  an  inclined  plane,  *,  I,  Jfc,  p.  497,  from  the  sea-level 
to  an  elevation  of  about  1500  feet,  near  the  entrance  of  the  Caldera,  this 
is  by  no  means  conclusive  in  favor  of  fluviatile  action,  although  some  ele- 
vated patches  of  the  same  may  in  truth  belong  to  an  old  river-bed ;  but 
in  South  America  gravel-beds  of  marine  origin  have  a  similar  upward 
slope,  when  followed  inland,  and  the  cause  of  such  an  arrangement  has 
been  explained  in  a  satisfactory  manner  by  Mr.  Darwin.* 

Another  argument  in  favor  of  marine  denudation  may  be  derived 
from  that  peculiar  feature  in  the  configuration  of  Palma,  before  alluded 
to,  called  the  pass  of  the  Cumbrecito  (e,  fig.  646,  p.  497),  forming  a 
notch  in  the  uppermost  line  of  precipices  surrounding  the  Caldera. 
This  break  divides  the  mountain  called  Alejanado,  </,  fig.  p.  497,  from 
the  eastern  wall  c,  /,  and  cuts  quite  through  the  upper  formation  ;  yet 
the  range  of  precipice  /,  e,  on  the  eastern  side  of  the  Caldera  is  con- 
tinued uninterruptedly,  and  retains  its  full  height  of  1500  or  2000  feet 
above  its  base,  to  the  southward  6f  the  Cumbrecito,  or  from  e  towards  a, 
map,  fig.  642,  p.  494.  In  this  prolongation  of  the  cliff  for  half  a  mile 
southward  beds  of  volcanic  matter  and  dikes  are  seen,  as  in  the  walls  of 
the  Caldera. 

The  indentation  forming  the  pass  of  the  Cumbrecito,  e,  p.  497,  has 
more  the  appearance  of  an  old  channel,  such  as  a  current  of  water  may 
have  excavated,  than  of  a  rent  or  a  chasm  caused  by  a  fault  In  case  or 
a  fault  the  lower  formation  would  not  be  persistent  and  uninterrupted 
across  the  Cumbrecito,  constituting  the  watershed ;  .  but  would  have 
sunk  down  and  have  been  replaced  by  the  upper  basaltic  rocks.  If 
*  Geolog.  Obaerv.,  South  America,  p.  43. 


CH.  XXIX.]  AQUEOUS   EROSION   IX   PALMA.  507 

we  could  assume  that  the  sea  once  entered  the  Caldera  here  as  well 
as  by  the  great  Barranco,  it  might  have  produced  such  a  breach  as  f, 
and  such  an  extension  of  the  line  of  cliffs  as  that  now  observable 
between  e  and  a,  map,  p.  494,  without  any  corresponding  cliff  to  the 
westward  of  e,  a. 

Yet  we  could  discover  no  elevated  outliers  of  conglomerate  to  attest 
the  supposed  erosion  at  the  Cumbrecito,  which  is  about  3500  feet  above 
the  level  of  the  sea.  It  might  also  be  objected  to  the  hypothesis  of  ma- 
rine denudation  in  Palma,  that  there  are  no  ranges  of  ancient  sea-cliffs  on 
the  external  slopes  of  the  island.  The  flanks  of  the  mountain,  except 
where  it  is  furrowed  by  ravines  or  broken  by  lateral  cones,  descend  to  the 
sea  with  a  uniform  inclination.  In  reply  to  such  a  remark,  I  may  ob- 
serve that  we  do  not  require  the  submergence  of  the  uppermost  3000  feet 
of  the  old  cone  in  order  to  allow  the  sea  to  enter  both  the  great  Bar- 
ranco and  the  Cumbrecito  and  to  flow  into  the  Caldera.  It  would  be 
enough  to  suppose  the  land  to  sink  down  so  as  to  permit  the  waves  to 
wash  the  base  of  the  basaltic  cliffs  in  the  interior  of  the  Caldera,  and  to 
wear  a  passage  through  the  Cumbrecito  where  there  may  have  been 
always  a  considerable  depression  in  the  outline  of  the  upper  formation. 
But  would  not  the  same  waves  which  had  power  to  form  in  the  Bar- 
ranco a  mass  of  conglomerate  800  feet  thick  have  left  memorials  of  their 
beach-action  on  the  external  slope  of  the  island  ?  No  such  monuments 
are  to  be  seen.  It  may  be  said,  in  explanation, — first,  that  cliffs  are  not 
so  easily  cut  on  the  side  of  an  island  towards  which  the  beds  dip  as  on 
the  side  from  which  they  dip ;  secondly,  if  some  small  cliffs  and  sea- 
beaches  had  existed,  they  may  have  been  subsequently  buried  under 
showers  of  ashes  and  currents  of  lava  proceeding  from  lateral  cones  during 
eruptions  of  the  same  date  as  those  which  were  certainly  contemporaneous 
with  the  conglomerate  of  the  great  Barranco. 

On  the  eastern  coast  of  Palma,  about  half  a  mile  from  the  sea,  in 
the  ravine  of  Las  Nieves,  not  far  from  Santa  Cruz,  we  observed  a  con- 
glomerate of  well-rounded  pebbles  having  a  thickness  of  100  feet, 
covered  by  successive  beds  of  lava,  also  about  100  feet  thick.  In  this 
instance  the  ancient  gravel  beds  occupy  a  position  very  analogous  to  the 
buried  cone,  S.P.,  fig.  645,  p.  496.  When  in  Palma,  I  conceived  them 
to  be  of  fluviatile  origin  ;  but,  whether  marine  or  freshwater,  it  must  be 
admitted  that  the  superposition  of  so  dense  an  accumulation  of  lavas 
to  a  mass  of  conglomerate  100  feet  thick  shows  how  easily  the  outer 
slopes  of  the  island  may  have  been  denuded  by  the  sea  and  yet  dis- 
play no  superficial  signs  of  marine  denudation,  every  old  beach  or  delta 
once  at  the  mouth  of  a  torrent  being  concealed  under  newer  volcanic  out- 
pourings. 

Since  the  cessation  of  volcanic  action  in  the  north  of  Palma,  the  most 
frequent  eruptions  appear  to  have  taken  place  in  a  line  running  north  and 
south,  from  a  to  Fuencaliente,  map,  p.  494 ;  one  of  the  volcanoes  in  this 
range,  called  Verigojo,  g,  being  no  less  than  6565  English  feet  high. 
The  lavas  descending  from  several  vents  in  this  chain  reach  the  sea  both 


508 


ISLAND   OF   ST.   PAUL. 


[Cn.  XXIX. 


on  the  east  and  west  coast,  and  are  many  of  them  nearly  as  naked  and 
barren  of  vegetation  as  when  they  first  flowed.  The  tendency  in  vol- 
canic vents  to  assume  a  linear  arrangement,  as  seen  in  the  volcanoes  of 
the  Andes  and  Java  on  a  grand  scale,  is  exemplified  by  the  cones  and 
craters  of  this  small  range  in  Palma.  It  has  been  conjectured  that  such 
linearity  in  the  direction  of  superficial  outbreaks  is  connected  with  deep 
fissures  in  the  earth's  crust  communicating  with  a  subjacent  focus  of  sub- 
terranean heat. 

By  discussing  at  so  much  length  the  question  whether  the  sea  may  or 
may  not  have  played  an  important  part  in  enlarging  the  Caldera  of 
Palma,  I  have  been  desirous  at  least  to  show  how  many  facts  and  obser- 
vations are  required  to  explain  the  structure  and  configuration  of  such 
volcanic  islands.  It  may  be  useful  to  cite,  in  illustration  of  the  same  sub- 
ject, the  present  geographical  condition  of  St.  Paul's  or  Amsterdam 
Island,  in  the  Indian  Ocean,  midway  between  the  Cape  of  Good  Hope  and 
Australia. 


Fig.  648. 


Map  of  the  Island  of  St.  Paul,  in  the  Indian  Ocean,  lat.  38°  44'  S.,  long.  77°  37'  E., 
surveyed  by  Capt.  Blackwood,  E.  N.,  1842. 

In  this  case  the  crater  is  only  a  mile  in  diameter  and  180  feet  deep, 
and  the  surrounding  cliffs  where  loftiest  about  800  feet  high  so  that  in 
regard  to  size  such  a  cone  and  crater  are  insignificant  when  compared 
to  the  cone  and  Caldera  of  Palma  or  to  such  volcanic  domes  as  Mounts 
Loa  and  Kea  in  the  Sandwich  Islands.  But  the  Island  of  St.  Paul  ex- 
emplifies a  class  of  insular  volcanoes  into  which  the  ocean  now  enters  by 


CttXXIX.]  ISLAND   OF  ST.   PAUL. — TEXERIFFE.  509 

Fig.  649. 


View  of  the  Crater  of  the  Island  of  St  Paul 
Fig.  650. 


Side  view  of  the  Island  of  St  Paul  (N.  E.  side).    Nine-pin  rocks  two  miles  distmnt 
(Captain  Blackwood.) 

a  single  passage.  Every  crater  must  almost  invariably  have  one  side 
much  lower  than  all  the  others,  namely  that  side  towards  which  the 
prevailing  winds  never  blow,  and  to  which,  therefore,  showers  of  dust 
and  scoriae  are  rarely  carried  during  eruptions.  There  will  also  be  one 
point  on  this  windward  or  lowest  side  more  depressed  than  all  the  rest, 
by  which  in  the  event  of  a  partial  submergence  the  sea  may  enter  as 
often  as  the  tide  rises,  or  as  often  as  the  wind  blows  from  that  quarter. 
For  the  same  reason  that  the  sea  continues  to  keep  open  a  single  entrance 
into  the  lagoon  of  an  atoll  or  annular  coral  reef,  it  will  not  allow  this  pas- 
sage into  the  crater  to  be  stopped  up,  but  will  scour  it  out  at  low  tide,  or 
as  often  as  the  wind  changes.  The  channel,  therefore,  will  always  be 
deepened  in  proportion  as  the  island  rises  above  the  level  of  the  sea,  at 
the  rate  perhaps  of  a  few  feet  or  yards  in  a  century. 

The  crater  of  Vesuvius  in  1822  was  2000  feet  deep  ;  and,  if  it  were  a 
half-submerged  cone  like  St  Paul,  the  excavating  power  of  the  ocean 
might  in  conjunction  with  a  gradual  upheaving  force  give  rise  to  a  large 
caldera.  Whatever,  therefore,  may  have  been  the  nature  of  the  forces, 
igneous  or  aqueous,  which  have  shaped  out  the  Val  del  Bove  on  Etna  or 
the  deep  abyss  called  the  Caldera  in  the  north  of  Palma,  we  can  scarcely 
doubt  that  many  craters  have  been  enlarged  into  calderas  by  the  denuding 
power  of  the  ocean,  whenever  considerable  oscillations  in  the  relative  level 
of  land  and  sea  have  occurred. 

Peak  of  Teneri/e. — The  accompanying  view  of  the  Peak,  taken  from 
sketches  made  by  Mr.  Hartung  and  myself  during  our  visit  to  Teneriffe 


510 


VIEW   OF   PEAK  OF  TENERIFFE. 


[Cn.  XXIX. 


II, 


•*"     rf 
I     s 

•a    s 


o          A., 
•S      cSi 


^"^? 


CH.  XXIX.]  PEAK   OF   TEXERIFFE.  511 

in  1854,  will  show  the  manner  in  which  that  lofty  cone  is  encircled  on 
more  than  two  sides  by  what  I  consider  as  the  ruins  of  an  older  cone, 
chiefly  formed  by  eruptions  from  a  summit  which  has  disappeared.  That 
ancient  culminating  point  from  which  one  or  more  craters  probably 
poured  forth  their  lavas  and  ejectamenta  may  not  have  been  placed  pre- 
cisely where  the  present  peak  now  rises,  and  may  not  have  had  the  same 
form,  but  its  position  was  probably  not  materially  different.  The  great 
wall  or  semicircular  range  of  precipices,  c  c,  surrounding  the  atrium,  b  6, 
is  obviously  analogous  to  the  walls  of  a  Caldera  like  that  of  Palma ;  but 
here  the  cliffs  are  insignificant  in  dimensions  when  compared  to  those  in 
Palma,  being  in  general  no  more  than  500  feet  high,  and  rarely  exceeding 
1000  feet.  The  plain  or  atrium,  b  6,  figs.  651  and  652,  lying  at  the  base 
of  the  cliffs,  is  here  called  Las  Canadas,  and  is  covered  with  sand  and 
pumice  thrown  out  from  the  Peak  or  from  craters  on  its  flanks.  Copious 
streams  of  lava,  d  d,  have  also  flowed  down  from  lateral  openings,  es- 
pecially from  a  crater  called  the  Chahorra,/,  fig.  652,  which  is  not  seen 
in  the  view,  fig.  651,  as  it  is  hidden  by  the  Peak.  The  last  eruption  was 
as  late  as  the  year  1798. 


s.  w.  N.  E. 

Section  through  part  of  Teneriffe,  from  N.  E.  to  8.  W.    On  a  true  scale ;  as  given  in 
Von  Bnch's  "  Canary  Islands." 

a.  Peak  of  Teneriffe.  J.  The  Canadas  or  atrium. 

c.  Cliff  bounding  the  atrium.  d.  Modern  lavas. 

f.  Cone  and  crater  of  Chahorra. 

To  what  extent  the  lavas,  d  d,  figs.  651,  and  652,  may  have  narrowed 
the  circus  or  atrium,  6,  or  taken  away  from  the  height  of  the  cliff  c,  no 
geologist  can  determine  for  want  of  sections ;  but  should  the  Peak  and 
the  Chahorra  continue  to  be  active  volcanoes  for  ages,  the  new  cone,  a, 
might  become  united  with  the  old  one,  and  the  lava  might  flow  first  from 
e  to  c  and  then  from  a  to  c,  fig.  652,  so  that  the  slope  might  begin  to 
resemble  that  formed  by  lavas  and  ejectamenta  from  the  summit  a  to 
Guia,  on  the  southwestern  side  of  the  cone. 

Madeira. — Every  volcanic  island,  so  far  as  I  have  examined  them, 
varies  from  every  other  one  in  the  details  of  its  geographical  and  geo- 
logical structure  so  greatly,  that  I  have  no  expectation  of  finding  any 
simple  hypothesis,  like  that  of  "  elevation  craters,"  applicable  to  all  or 
capable  of  explaining  their  origin  and  mode  of  growth.  Few  islands, 
for  example,  resemble  each  other  more  than  Madeira  and  Palma,  inas- 
much as  both  consist  mainly  of  basaltic  rocks  of  subaerial  origin,  but, 
when  we  compare  them  closely  together,  there  is  no  end  of  the  points  in 
which  they  differ. 

The  oldest  formation  known  in  Madeira  is  of  submarine  volcanic  origin, 


512  ISLAND   OF   MADEIEA.  [On.  XXIX. 

and  referable  perhaps  to  the  Miocene  tertiary  epoch.  Tuffs  and  lime- 
stones containing  marine  shells  and  corals  occur  at  S.  Vicente  on  the 
northern  coast,  where  they  rise  to  the  height  of  more  than  1200  feet 
above  the  sea.  They  bear  testimony  to  an  upheaval  to  that  amount,  at 
least,  since  the  commencement  of  volcanic  action  in  those  parts. 

The  pebbles  in  these  marine  beds  are  well  rounded  and  polished, 
strongly  contrasting  in  that  respect  with  the  angular  fragments  of  similar 
varieties  of  volcanic  rocks  so  frequent  in  'the  superimposed  tuffs  and  ag- 
glomerates formed  above  the  level  of  the  sea. 

The  length  of  Madeira  from  east  to  west  is  about  30  miles,  its  breadth 
from  north  to  south  being  12  miles.  The  annexed  section,  fig.  653, 
drawn  up  on  a  true  scale  of  heights  and  horizontal  distances  from  the 
observations  of  Mr.  Hartung  and  myself,  will  enable  the  reader  to  com- 
prehend some  of  the  points  in  which,  geologically  considered,  Madeira 
resembles  or  varies  from  Palma.  In  the  central  region,  at  A,  as  well 
as  in  the  adjoining  region  on  each  side  of  it,  are  seen,  as  in  the  centre 
of  Palma,  a  great  number  of  dikes  penetrating  through  a  vast  accumu- 
lation of  ejectamenta,  c.  Here  also,  as  in  Palma,  we  observe  as  we 
recede  from  the  centre  that  the  dikes  decrease  in  number,  and  beds  of 
scoriae,  lapilli,  agglomerate,  and  tuff  begin  to  alternate  with  stony  lavas, 
d  d,  until  at  the  distance  of  a  mile  or  more  from  the  central  axis  of  the 
volcanic  mass,  below  /  h  and  e  g,  consists  almost  exclusively  of  streams 
or  sheets  of  basalt,  with  some  red  partings  of  ochreous  clay  or  laterite, 
probably  ancient  soils.  The  darker  lines  indicate  the  predominance 
of  these  lavas  which  have  flowed  on  the  surface,  and  which,  besides 
basalt,  consist  of  various  kinds  of  trap,  and  in  some  places  of  trachyte. 
The  lighter  tint,  c,  expresses  an  accumulation  of  scoria?,  agglomerate, 
and  other  materials,  such  as  may  have  been  piled  up  in  the  open 
air,  in  or  around  the  chief  orifices  of  eruption,  and  between  volcanic 
cones. 

The  Pico  Torres,  A,  more  than  6000  feet  high,  is  one  of  many  central 
peaks,  composed  of  ejected  materials.  By  the  union  of  the  foundations 
of  many  similar  peaks,  ridges  or  mountain  crests  are  formed,  from  which 
the  tops  of  vertical  dikes  project  like  turrets  above  the  weathered  surface 
of  the  softer  beds  of  tuff  and  scoriaB.  Hence  the  broken  and  picturesque 
outline,  giving  a  singular  and  romantic  character  to  the  scenery  of  the 
highest  part  of  Madeira.  North  of  A  is  seen  Pico  Ruivo  (B),  the  most 
elevated  peak  in  the  island,  yet  exceeding  by  a  few  feet  only  the  height 
of  Pico  Torres.  It  is  similar  in  composition,  but  its  uppermost  part, 
400  feet  high,  retains  a  more  perfectly  conical  form,  and  has  a  dike  at 
its  summit  with  streams  of  scoriaceous  lava  adhering  to  its  steep  flanks. 
There  are  a  great  many  such  peaks  east  and  west  of  A,  which  seem  to  be 
the  ruins  of  cones  of  eruption,  the  materials  of  some  at  least  having 
been  arranged  with  a  qua-qua-versal  dip.  Among  these  is  Pico  Grande, 
c,  fig.  655,  now  half-buried  under  more  modern  lavas  which  have 
flowed  round  it.  It  is  perhaps  owing  to  the  juxtaposition  of  such  a 
multitude  of  cones  or  points  of  eruption,  and  the  interference  of  their 


CH.  XXIX.] 


SECTION  OF  MADEIRA. 


513 


Iliitt 

r?  f ?r ° 


314  FOSSIL  PLANTS  OF  MADEIRA.  [On.  XXIX, 

lavas  along  the  great  east  and  west  line  of  volcanic  action,  that  wo 
find  the  stony  beds  in  the  central  region  between  e  and  /,  fig.  653, 
nearly  horizontal,  or  having  a  dip  of  no  more  than  from  3  to  5  degrees, 
instead  of  having  a  very  steep  inclination  like  those  in  the  walls  of  the 
Caldera  of  Palma. 

These  level  or  slightly  inclined  beds  often  form  platforms,  such  as  that 
called  the  Paul  de  Serra  (or,  fig.  p.  516).  But  when  we  recede  from  the 
central  axis,  the  lavas  acquire  an  average  slope  of  10  degrees  on  the 
north  (as  between  e  and  g,  fig.  653),  and  of  15  on  the  south  between 
/  and  h.  Nearer  the  sea  again,  as  at  i  and  L,  where  the  most  modern 
lavas  occur,  the  dip  diminishes  to  5  degrees,  and  even  to  3  J,  as  at  K,  near 
Funchal.  In  this  latter  characteristic,  however  (tie  smaller  inclination  of 
the  lavas  near  the  sea,  and  their  association  there  with  modern  cones  of 
eruption,  such  as  M,  N,  o),  there  is  a  strict  analogy  between  Madeira  and 
Palma.  Buried  cones  of  eruption  also  occur  at  many  points,  as  at  p 
and  <?,  fig.  653,  which  have  been  overwhelmed  by  lavas  flowing  from  the 
central  region.  The  aggregate  thickness  of  the  more  solid  basalts  alter- 
nating with  tuffs  rarely  exceeds  1500  feet ;  but  below  Pico  S.  Antonio, 
or  K,  fig.,  p.  513,  they  attain  a  thickness  of  3000  feet,  being  exposed  to 
view  on  the  sides  of  a  deep  valley  called  the  Curral,  presently  to  be 
mentioned. 

As  a  general  rule,  the  lavas  of  Madeira,  whether  vesicular  or  compact, 
do  not  constitute  continuous  sheets  parallel  to  each  other.  When  viewed 
in  the  sea-cliffs  in  sections  transverse  to  the  direction  in  which  they 
flowed,  they  vary  greatly  in  thickness,  even  if  followed  for  a  few  hundred 
feet  or  yards,  and  they  usually  thin  out  entirely  in  less  than  a  quarter  of 
a  mile.  In  the  ravines  which  radiate  from  the  centre  of  the  island, 
the  beds  are  more  persistent,  but  even  here  they  usually  are  seen 
to  terminate,  if  followed  for  a  few  miles ;  their  thickness  also  being 
very  variable,  and  sometimes  increasing  suddenly  from  a  few  feet  to 
many  yards. 

I  saw  no  remains  of  fossil  plants  in  any  of  the  red  partings  or  laterites 
above  alluded  to;  but  Mr.  Smith,  of  Jordanhill,  was  more  fortunate  in 
1 840,  having  met  with  the  carbonized  branches  and  roots  of  shrubs  in 
some  red  clays  under  basalt  near  Funchal.  Nevertheless,  Mr.  Hartung 
and  I  obtained  satisfactory  evidence  in  the  northern  part  of  the  island,  in 
the  ravine  of  S.  Jorge,  of  the  former  existence  of  terrestrial  vegetation, 
and  consequently  of  the  subaerial  origin  of  a  large  portion  of  the  lavas' of 
Madeira.  At  q  in  the  section  (fig.  653)  the  occurrence  of  a  bed  of  im- 
pure lignite,  covered  by  basalt,  had  long  been  known.  Associated  with 
it,  we  observed  several  layers  of  tuff  and  clay  or  hardened  mud,  in  one  of 
which  leaves  of  dicotyledonous  plants  and  of  ferns  abound.  The  latter, 
according  to  Mr.  Charles  J.  F.  Bunbury,  are  referable  to  the  genera 
Sphenopteris,  Adiantum?,  Pecopteris,  and  Woodwardia,  one  of  them 
having  the  peculiar  venation  of  Woodwardia  radicans,  a  species  now 
common  in  Madeira.  Among  the  dicotyledonous  leaves,  some  are  ap- 
parently of  the  myrtle  family,  the  larger  proportion  having  their  surfaces 


Cn.  XXIX.]  CRATER   OF  LAGOA.  515 

smooth  and  unwrinkled,  with  a  somewhat  rigid  and  coriaceous  texture, 
and  with  undivided  or  entire  margins.  "  These  characters,"  observes  Mr. 
Bunbury,  "  belong  to  the  laurel-type,  and  indicate  a  certain  analogy  be- 
tween the  ancient  vegetable  remains  and  the  modern  forests  of  Ma- 
deira, in  which  laurels  and  other  evergreens  abound,  with  glossy  cori 
aceous  and  entire-edged  leaves,  while  below  them  there  is  an  under- 
growth of  ferns  and  other  plants." 

The  lignite  above  mentioned  and  the  leaf-bed  occur  at  the  height  of 
1000  feet  above  the  level  of  the  sea,  and  are  overlaid  by  superimposed 
basalts  and  scoria3,  1100  feet  thick,  implying  the  existence  of  an  ancient 
terrestrial  vegetation  long  before  a  large  part  of  Madeira  had  been  built 
up.  The  nature  of  the  tuffs  accompanying  the  lignite,  together  with 
some  agglomerates  in  the  vicinity,  entitles  us  to  presume  that  near  this 
spot  a  series  of  eruptions  once  broke  out.  Nor  is  it  improbable  that 
there  may  have  been  here  the  crater  of  some  lateral  cone  in  which  the 
lignite  and  leaf-bed  accumulated ;  for,  although  craters  are  remarkably 
rare  in  Madeira,  when  we  consider  how  considerable  is  the  number  of 
perfect  cones,  yet  on  the  mountain  called  Lagoa,  2J  miles  west  of 
Machico,  a  crater  as  perfect  as  that  of  Astroni  near  Naples  may  be  seen. 

At  the  bottom  of  this  circular  cavity  (fig.  654),  which  is  about  150 
feet  deep,  is  a  plain  about  500  feet  in  diameter,  having  a  pond  in  the 
middle,  towards  which  the  plain  slopes  gently  from"  all  sides.  Such 
ponds  are  often  seen  in  the  interior  of  extinct  craters.  Except  in  the 
middle  it  is  shallow,  and  supports  aquatic  plants.  Many  leaves  must  also 
be  blown  into  it  from  the  surrounding  heights  when  high  winds  prevail, 
so  that  a  mass  of  peaty  matter  convertible  into  lignite  may  collect  here. 

Fig.  654 


Crater  of  Lagoa,  2£  miles  west  of  Machico,  Madeira. 


In  this  cut,  taken  from  a  sketch  of  my  own,  the  depth  of  the  crater  may  appear 
too  great,  unless  it  is  borne  in  mind  that  there  are  no  trees  visible,  and  most  of 
the  bushes  are  of  the  Madeira  whortleberry  (  Vacciniwn  Madeirense)  five  or  six 
feet  high.  Immediately  behind  the  foreground  an  artificial  mound  is  seen  thrown 
up  as  a  fence. 

Had  streams  of  lava  descending  from  greater  heights  entered  this 
Lagoa  crater,  they  would  have  formed  dense  masses  of  compact  rock 


516  CENTRAL  VALLEYS.  [Cn.  XXIX. 

cooling  slowly  under  great  pressure,  like  those  now  incumbent  on  the 
impure  lignite  of  S.  Jorge.  The  dip  of  the  latter  cannot  be  clearly  deter- 
mined, since  it  is  exposed  to  view  for  too  short  a  distance  ;  and  the  same 
may  be  said  of  the  leaf-bed,  part  of  which  may  be  traced  lower  down 
the  ravine.  It  seems,  however,  to  dip  to  the  north  or  towards  the  sea 
conformably  with  the  general  inclination  of  the  basaltic  and  tufaceous 
strata. 

A  deep  valley,  called  the  Curral  (B,  fig.  655),  surrounded  by  precipices 
from  1500  to  2500  feet  high,  and  by  peaks  of  still  greater  elevation^ 
occurs  in  the  middle  of  Madeira.  It  has  been  compared  by  some  to  a 
crater  or  caldera,  for  its  upper  portion  is  situated  in  the  region  where 
dikes  and  ejectamenta  abound.  The  Curral,  however,  extends,  without 
diminishing  in  depth,  to  below  the  region  of  numerous  dikes,  and  it  lays 
open  to  view  all  the  beds  R,  s,  fig.  653.  Nor  do  the  volcanic  masses  dip 
away  in  all  directions  from  the  Curral,  as  from  a  central  point,  or  from 
the  hollow  axis  of  a  cone.  The  Curral  is  in  fact  one  only  of  three 
great  valleys  which  radiate  from  the  most  mountainous  district,  a  second 
depression,  called  the  Serra  d'Agoa  (D,  fig.  655),  being  almost  as  deep. 
This  cavity  is  also  drained  by  a  river  flowing  to  the  south  ;  while  a  third 
valley,  namely,  that  of  the  Janella,  sends  its  waters  to  the  north.  The 
section  alluded  to  (fig.  655),  passing  through  part  of  the  axis  of  the 
island  in  an  E.  and  W.  direction,  shows  how  the  Curral  and  Serra 
d'Agoa,  B  and  D,  are  separated  by  a  narrow  and  lofty  ridge,  c,  part  of 


"West.  East. 


Section  through  the  central  region  of  Madeira,  from  East  to  West. 

A.  Part  of  the  platform,  called  the  Paul  da  Serra.        B.  Curral ;  a  valley,  3000  feet  deep. 
C.  Pico  Grande.  D.  The  valley  of  the  Serra  d'Agoa. 

which  is  surmounted  by  the  Pico  Grande,  before  mentioned,  nearly  5400 
feet  high.  There  is  no  essential  difference  between  the  shape  of  these 
three  great  valleys  and  many  of  those  in  the  Alps  and  Pyrenees,  where 
the  valley-making  process  can  have  had  no  connection  with  any  superfi- 
cial volcanic  action. 

In  the  Alps,  no  doubt,  as  in  other  lofty  chains,  the  formation  of  val- 
leys has  been  greatly  aided  by  subterranean  movements,  both  gradual 
and  violent,  and  by  the  dislocation  of  rocks.  The  same  may  be  true  of 
Madeira  and  of  almost  every  lofty  volcanic  region ;  but,  when  we  reflect 
that  the  central  heights  A  and  B,  fig.  653,  are  more  than  6000  feet  above 
the  sea,  and  that  the  waters  flowing  from  them,  swollen  by  melted  snows, 
reach  the  sea  by  a  course  of  not  much  more  than  6  miles  in  the  case  of 
those  draining  the  Curral,  and  by  nearly  as  short  a  route  in  the  Serra 
d'Agoa,  we  shall  be  prepared  for  almost  any  amount  of  denudation  effected 
simply  by  subaerial  erosion. 


CH.  XXIX.]  TRACKYTIC  KOCKS.  517 

The  general  absence  of  water-worn  pebbles  in  the  tuffs  underlying  the 
Madeira  lavas  is  very  striking,  and  contrasts  with  the  frequent  occurrence 
of  gravel-beds  under  so  many  of  the  Auvergne  lavas.  It  simply  proves 
that  Madeira,  like  the  volcanic  mountains  of  Java,  or  like  Mount  Etna  or 
Mona  Loa  in  the  Sandwich  Islands,  could  not,  for  reasons  before  given, 
p.  475,  support  a  single  torrent  so  long  as  eruptions  were  frequent  on  its 
slopes.  The  period,  therefore,  of  fluviatile  erosion  must  have  been  sub- 
sequent to  the  formation  of  the  central  nucleus  of  ejectamenta,  c,  fig., 
p.  513,  and  of  the  lavas,  c?,  ibid.  When  we  infer  that  these  were  of 
supramarine  origin  as  far  down  as  the  line  p,  ,  t,  and  perhaps  lower,  it 
follows  that  a  lofty  island,  4000  feet  or  more  in  height,  must  have  resulted, 
even  if  no  upheaval  had  ever  occurred. 

The  movements  which  upraised  the  marine  deposits  of  San  Vicente 
may  or  may  not  have  extended  over  a  wide  area.  How  far  they  modified 
the  form  of  the  island,  or  added  to  its  height,  is  a  fair  subject  of  specula- 
tion ;  and  whether  the  steep  dip  of  the  lavas  seen  in  the  ravines  inter- 
secting the  slopes  of  the  mountain,  /  h  and  e  g,  can  be  ascribed  1  o  such 
movements.  The  lavas  of  more  modern  date,  near  Funchal,  may  be 
imagined  to  remain  comparatively  horizontal,  because  they  have  escaped 
the  influence  of  disturbing  forces  to  which  the  older  nucleus  was  exposed. 
Without  discussing  this  point  (so  fully  treated  of  in  reference  to  Palma), 
I  may  observe  that  unquestionably  different  parts  of  Madeira  have  been 
formed  in  succession.  Near  Porto  da  Cruz,  for  example,  on  the  northern 
coast,  trachytes  of  a  gray,  and  trachytic  tuffs  almost  of  a  white  color, 
in  slightly  inclined  or  almost  horizontal  beds,  have  partially  filled  up 
deep  valleys  previously  excavated  through  the  older  and  inclined  basaltic 
rocks  (dipping  at  an  angle  of  10°  to  the  north),  under  which  the  leaf-bed 
and  lignite  before  mentioned,  fig.  653,  p.  513,  lie  buried.  During  the 
convulsions  which  accompanied  the  outpouring  of  every  newer  series  of 
lavas,  the  older  rocks  may  have  been  more  or  less  disturbed  and  tilted, 
without  destroying  the  general  form  of  the  old  dome-shaped  mountain 
supposed  by  us  to  have  been  the  result  of  repeated  eruptions  from  the 
central  vents. 

The  locality  just  referred  to  of  Porto  da  Cruz  exemplifies,  not  only 
the  long  intervals  of  time  which  separated  the  outflowing  of  distinct  sets 
of  lavas,  but  also  the  precedence  of  the  basaltic  to  the  trachytic  out- 
pourings. So  also  on  the  southern  slope  of  Madeira,  I  observed  between 
the  Jardim  and  Pico  Bodes,  situated  in  a  direct  line  about  six  miles  north- 
west of  Funchal,  a  well-marked  series  of  trachytic  rocks  of  considerable 
thickness  occupying  the  highest  geological  position.  They  consist  of 
white  and  gray  trachytes,  occurring  at  points  varying  from  2500  to  3500 
feet  above  the  sea.  Their  position  may  be  understood  by  supposing 
them  to  constitute  the  uppermost  beds  represented  at  h  in  the  section, 
fig.  653,  p.  513,  and  on  the  slope  above  h.  The  doctrine,  therefore,  that 
in  each  series  of  volcanic  eruptions  the  trachytic  lavas  flow  out  first,  and 
after  them  the  basaltic  kinds  (see  p.  522),  is  by  no  means  borne  out  in 


518  LAVAS  OF  MADEIRA.    '  [Cu.  XXIX. 

Madeira,  although  some  of  the  newest  currents,  like  those  at  the  foot  of 
the  cones,  M,  N,  o,  fig.  653,  are  basaltic. 

I  may  here  allude  to  another  feature  in  the  mineralogical  structure  of 
Madeira,  namely,  that  most  commonly  the  uppermost  of  all  the  volcanic 
rocks,  when  we  ascend  to  heights  of  1200  feet  or  more  above  the  sea, 
consist  of  compact  felspathic  trap,  with  much  olivine,  separating  into 
spheroidal  masses  several  feet  in  diameter,  especially  when  some  of  the 
contained  iron  has  become  more  highly  oxidated  in  the  atmosphere.  M. 
Delesse,  after  examining  my  specimens,  informs  me  that  in  France  they 
would  call  this  rock  basalt,  although  it  is  often  without  augite,  and 
simply  a  mixture  of  blackish  green  felspar  with  olivine.  Whatever  name 
we  assign  to  it,  the  superficial  envelope  of  the  island,  not  only  in  the  line 
of  section  followed  in  fig.  653,  p.  513,  but  also  very  generally,  may  be 
said  to  consist  of  this  trap,  except  near  the  sea,  where  basalts  occur  which 
have  not  the  same  spheroidal  structure. 

Among  other  indications  of  a  considerable  difference  of  age,  e~xn  in 
the  superficial  volcanic  formations  of  Madeira,  I  may  remark,  that  many 
of  the  central  peaks,  such  as  A,  fig.  653,  seem  to  be  the  mere  skeletons 
of  cones  of  eruption  ;  whereas  the  forms  of  the  more  modern  cones,  such 
as  M,  N,  o,  are  regular,  and  have  no  protruding  dikes  on  their  summits  or 
flanks. 

The  newest  lavas  also  in  Madeira  have,  in  one  district  at  least,  a 
singularly  recent  aspect  as  compared  to  those  of  older  date,  which  are 
decomposed  superficially,  often  to  the  depth  of  several  feet  or  yards.  I 
allude  to  the  lava  currents  near  Port  Moniz,  one  of  which  is  as  rough 
and  bristling  as  are  some  streams  before  alluded  to  in  Pal  ma  (p.  508)  of 
historical  date.  I  am  indebted  to  Mr.  Hartung  for  the  annexed  drawing 
of  a  lava  at  Port  Moniz,  which  I  did  not  visit  myself.  It  is  traversed  by 

Fig.  656.        • 


Surface  of  lava  near  Port  Moniz,  N.  W.  point  of  Madeira;  from  a  drawing  by  M.  Hartung. 
a.  Channel  traversing  the  lava. 

a  channel,  a,  like  one  of  those  already  described,  p.  503.  For  how  long 
a  period  such  characters  may  be  retained  is  uncertain,  so  much  does  this 
depend  on  the  mineral  composition  of  the  rock.  Some  of  the  lavas  of 
Auvcrgne  of  prehistorical  date  and  certainly^  of  high  antiquity,  are  almost 
as  rugged  ;  so  that  this  freshness  of  aspect  is  only  a  probable  indication 
of  a  relatively  modem  origin. 


CH.  XXX.  1  TESTS   OF  AGE   OF  VOLCANIC   ROCKS.  519 

CHAPTER  XXX. 

ON   THE   DIFFERENT   AGES   OF   THE   VOLCANIC   ROCKS. 

Tests  of  relative  ages  of  volcanic  rocks — Tests  by  superposition  and  intrusion  — 
Dike  of  Quarrington  Hill,  Durham  —  Test  by  alteration  of  rocks  in  contact — 
Test  by  organic  remains — Test  of  age  by  mineral  character — Test  by  included 
fragments  —  Volcanic  rocks  of  the  Post-Pliocene  period  —  Basalt  of  Bay  of 
Trezza  in  Sicily — Post-Pliocene  volcanic  rocks  near  Naples — Dikes  of  Somma 
— Igneous  formations  of  the  Newer  Pliocene  period  —  Val  di  Noto  in  Sicily. 

HAVING  referred  the  sedimentary  strata  to  a  long  succession  of  geo- 
logical periods,  we  have  now  to  consider  how  far  the  volcanic  formations 
can  be  classed  in  a  similar  chronological  order.  The  tests  of  relative 
age  in  this  class  of  rocks  are  four  :  —  1st,  superposition  and  intrusion, 
with  or  without  alteration  of  the  rocks  in  contact ;  2d,  organic  remains  ; 
3d,  mineral  characters ;  4th,  included  fragments  of  older  rocks. 

Tests  by  superposition,  &c.  —  If  a  volcanic  rock  rests  upon  an  aqueous 
deposit,  the  former  must  be  the  newest  of  the  twc;  but  the  like  rule  does 
not  hold  good  where  the  aqueous  formation  rests  upon  the  volcanic,  for 
melted  matter,  rising  from  below,  may  penetrate  a  sedimentary  mass 
without  reaching  the  surface,  or  may  be  forced  in  conformably  between 
two  strata,  as  b  at  D  in  the  annexed  figure  (fig.  656),  after  which  it  may 
cool  down  and  consolidate.  Superposition,  therefore,  is  not  of  the  same 

Fig.  657. 
E D  


jull 


value  as  a  test  of  age  in  the  unstratified  volcanic  rocks  as  in  fossiliferous 
formations.  We  can  only  rely  implicitly  on  this  test  where  the  volcanic 
rocks  are  contemporaneous,  not  where  they  are  intrusive.  Now  they 
are  said  to  be  contemporaneous  if  produced  by  volcanic  action,  which 
was  going  on  simultaneously  with  the  deposition  of  the  strata  with  which 
they  are  associated.  Thus  in  the  section  at  D  (fig.  656),  we  may  per- 
haps ascertain  that  the  trap  b  flowed  over  the  fossiliferous  bed  c,  and 
that,  after  its  consolidation,  a  was  deposited  upon  it,  a  and  c  both  belong- 
ing to  the  same  geological  period.  But  if  the  stratum  a  be  altered  by 
b  at  the  point  of  contact,  we  must  then  conclude  the  trap  to  have  been 
intrusive,  or  if,  in  pursuing  b  for  some  distance,  we  find  at  length  that 
it  cuts  through  the  stratum  a,  and  then  overlies  it  as  at  E. 

We  may,  however,  be  easily  deceived  in  supposing  a  volcanic  rock  to 
be  intrusive,  when  in  reality  it  is  contemporaneous ;  for  a  sheet  of  lava, 
as  it  spreads  over  the  bottom  of  the  sea,  cannot  rest  every  where  upon 
the  same  stratum,  either  because  these  have  been  denuded,  or  because. 


520 


TESTS  OF  RELATIVE  AGE 


[On.  XXX. 


Fig.  658. 


if  newly  thrown  down,  they  thin  out  in  certain  places,  thus  allowing  the 
lava  to  cross  their  edges.  .Besides,  the  heavy  igneous  fluid  will  often,  as 
it  moves  along,  cut  a  channel  into  beds  of  soft  mud  and  sand.  Suppose 
the  submarine  lava  F,  fig.  658,  to  have 
come  in  contact  in  this  manner  with  the 
strata  a,  Z>,  c,  and  that  after  its  consolida- 
tion, the  strata  c?,  e,  are  thrown  down  in  a 
nearly  horizontal  position,  yet  so  as  to  lie 
unconformably  to  F,  the  appearance  of 
subsequent  intrusion  will  here  be  com- 
plete, although  the  trap  is  in  fact  con- 
temporaneous. We  must  not,  therefore,  hastily  infer  that  the  rock  F  is 
intrusive,  unless  we  find  the  strata  c?,  e,  or  c  to  have  been  altered  at  their 
junction,  as  if  by  heat. 

When  trap  dikes  were  described  in  the  preceding  chapter,  they  were 
shown  to  be  more  modern  than  all  the  strata  which  they  traverse.  A 
basaltic  dike  at  Quarrington  Hill,  near  Durham,  passes  through  coal- 
measures,  the  strata  of  which  are  inclined,  and  shifted  so  that  those  on 
the  north  side  of  the  dike  are  24  feet  above  the  level  of  the  correspond- 

Fig.  659. 
Magnesian  limestone. 


Coal.  Dike.  Coal. 

Section  at  Quarrington  Hill,  east  of  Durham.    (Sedgwick.) 
a.  Magnesian  Limestone  (Permian).  6.  Lower  New  Red  Sandstone, 

c.  Coal  strata. 

ing  beds  on  the  south  side  (see  section,  fig.  659).  But  the  horizontal 
beds  of  overlying  Red  Sandstone  and  Magnesian  Limestone  are  not  cut 
through  by  the  dike.  Now  here  the  coal-measures  were  not  only  depos- 
ited, but  had  subsequently  been  disturbed,  fissured,  and  shifted,  before 
the  fluid  trap  now  forming  the  dike  was  introduced  into  a  rent.  It  is 
also  clear  that  some  of  the  upper  edges  of  the  coal  strata,  together  with 
the  upper  part  of  the  dike,  had  been  subsequently  removed  by  denuda- 
tion before  the  lower  New  Red  Sandstone  and  Magnesian  Limestone 
were  superimposed.  Even  in  this  case,  however,  although  the  date  of 
the  volcanic  eruption  is  brought  within  narrow  limits,  it  cannot  be  defined 
with  precision ;  it  may  have  happened  either  at  the  close  of  the  Carbo- 
niferous period,  or  early  in  that  of  the  Lower  New  Red  Sandstone,  or 
between  these  two  periods,  when  the  state  of  the  animate  creation  and 
the  physical  geography  of  Europe  were  gradually  changing  from  the  type 
of  the  Carboniferous  era  to  that  of  the  Permian. 


Cn.  XXX.]  OF  VOLCANIC  ROCKS.  521 

The  test  of  age  by  superposition  is  strictly  applicable  to  all  stratified 
volcanic  tuffs,  according  to  the  rules  already  explained  in  the  case  of 
other  sedimentary  deposits.  (See  p.  97.) 

Test  of  age  by  organic  remains. — We  have  seen  how,  in  the  vicinity 
of  active  volcanos,  scoriae,  pumice,  fine  sand,  and  fragments  of  rock  are 
thrown  up  into  the  air,  and  then  showered  down  upon  the  land,  or  into 
neighboring  lakes  or  seas.  In  the  tuffs  so  formed  shells,  corals,  or  any 
other  durable  organic  bodies  which  may  happen  to  be  strewed  over  the 
bottom  of  a  lake  or  sea  will  be  imbedded,  and  thus  continue  as  permanent 
memorials  of  the  geological  period  when  the  volcanic  eruption  occurred. 
Tufaceous  strata  thus  formed  in  the  neighborhood  of  Vesuvius,  Etna,  Strom- 
boli,  and  other  volcanos  now  active  in  islands  or  near  the  sea,  may  give 
information  of  the  relative  age  of  these  tuffs  at  some  remote  future  period 
when  the  fires  of  these  mountains  are  extinguished.  By  evidence  of  this 
kind  we  can  establish  a  coincidence  in  age  between  volcanic  rocks,  and 
the  different  primary,  secondary,  and  tertiary  fossiliferous  strata. 

The  tuffs  alluded  to  may  not  always  be  marine,  but  may  include,  in 
some  places,  freshwater  shells ;  in  others,  the  bones  of  terrestrial  quad- 
rupeds. The  diversity  of  organic  remains  in  formations  of  this  nature  is 
perfectly  intelligible,  if  we  reflect  on  the  wide  dispersion  of  ejected  matter 
during  late  eruptions,  such  as  that  of  the  volcano  of  .Coseguina,  in  the 
province  of  Nicaragua,  January  19,  1835.  Hot  cinders  and  fine  scoriaa 
were  then  cast  up  to  a  vast  height,  and  covered  the  ground  as  they  fell 
to  the  depth  of  more  than  10  feet,  and  for  a  distance  of  8  leagues  from 
the  crater  in  a  southerly  direction.  Birds,  cattle,  and  wild  animals  were 
scorched  to  death  in  great  numbers,  and  buried  in  ashes.  Some  volcanic 
dust  fell  at  Chiapa,  upwards  of  1200  miles,  not  to  leeward  of  the  volcano, 
as  might  have  been  anticipated,  but  to  windward,  a  striking  proof  of  a 
counter  current  in  the  upper  region  of  the  atmosphere  ;  and  some  on  Ja- 
maica, about  700  miles  distant  to  the  northeast.  In  the  sea,  also,  at  the 
distance  of  1100  miles  from  the  point  of  eruption,  Captain  Eden  of  the 
Conway  sailed  40  miles  through  floating  pumice,  among  which  were  some 
pieces  of  considerable  size.* 

Test  of  age  by  mineral  composition. — As  sediment  of  homogeneous 
composition,  when  discharged  from  the  mouth  of  a  large  river,  is  often 
deposited  simultaneously  over  a  wide  space,  so  a  particular  kind  of  lava, 
flowing  from  a  crater  during  one  eruption,  may  spread  over  an  extensive 
area;  as  in  Iceland  in  1783,  when  the  melted  matter,  pouriug  from 
Skaptar  Jokul,  flowed  in  streams  in  opposite  directions,  and  caused  a 
continuous  mass,  the  extreme  points  of  which  were  90  miles  distant  from 
each  other.  This  enormous  current  of  lava  varied  in  thickness  from  100 
feet  to  600  feet,  and  in  breadth  from  that  of  a  narrow  river  gorge  to  15 
miles.f  Now,  if  such  a  mass  should  afterwards  be  divided  into  separate 

*  Caldcleugh,  Phil.  Trans.  1836,  p.  27. 
f  See  Principles,  Index,  "Skaptar  Jokul." 


522        RELATIVE  AGES  OF  VOLCANIC  ROCKS.    [On.  XXX. 

fragments  by  denudation,  we  might  still  perhaps  identify  the  detached 
portions  by  their  similarity  in  mineral  composition.  Nevertheless,  this 
test  will  not  always  avail  the  geologist ;  for,  although  there  is  usually  a 
prevailing  character  in  lava  emitted  during  the  same  eruption,  and  even 
in  the  successive  cirfrents  flowing  from  the  same  volcano,  still,  in  many 
cases,  the  different  parts  even  of  one  lava-stream,  or,  as  before  stated,  of 
one  continuous  mass  of  trap,  vary  much  in  mineral  composition  and 
texture. 

In  Auvergne,  the  Eifel,  and  other  countries  where  trachyte  and  basalt 
are  both  present,  the  trachytic  rocks  are  for  the  most  part  older  than  the 
basaltic.  These  rocks  do,  indeed,  sometimes  alternate  partially,  as  in  the 
volcano  of  Mont  Dor,  in  Auvergne  ;  and  we  have  seen  that  in  Madeira 
trachytic  rocks  may  overlie  an  older  basaltic  series  (p.  517)  ;  but  the  great 
mass  of  trachyte  occupies  more  generally,  perhaps,  an  inferior  position,  and 
is  cut  through  and  overflowed  by  basalt.  It  can  by  no  means  be  inferred 
that  trachyte  predominated  at  one  period  of  the  earth's  history  and  basalt 
at  another,  for  we  know  that  trachytic  lavas  have  been  formed  at  many 
successive  periods,  and  are  still  emitted  from  many  active  craters  ;  but  it 
seems  that  in  each  region,  where  a  long  series  of  eruptions  have  occurred, 
the  more  felspathic  lavas  have  been  first  emitted,  and  the  escape  of  the 
more  augitic  kinds  has  followed.  The  hypothesis  suggested  by  Mr. 
Scrope  may,  perhaps,  afford  a  solution  of  this  problem.  The  minerals, 
he  observes,  which  abound  in  basalt  are  of  greater  specific  gravity  than 
those  composing  the  felspathic  lavas ;  thus,  for  example,  hornblende, 
augite,  and  olivine  are  each  more  than  three  times  the  weight  of  water ; 
whereas  common  felspar,  albite,  and  Labrador  felspar,  have  each  scarcely 
more  than  2^  times  the  specific  gravity  of  water  ;  and  the  difference  is 
increased  in  consequence  of  there  being  much  more  iron  in  a  metallic 
state  in  basalt  and  greenstone  than  in  trachyte  and  other  felspathic  lavas 
and  trap  rocks.  If,  therefore,  a  large  quantity  of  rock  be  melted  up 
in  the  bowels  of  the  earth  by  volcanic  heat,  the  denser  ingredients  of 
the  boiling  fluid  may  sink  to  the  bottom,  and  the  lighter  remaining 
above,  would  in  that  case  be  first  propelled  upwards  to  the  surface 
by  the  expansive  power  of  gases.  Those  materials,  therefore,  which 
occupied  the  lowest  place  in  the  subterranean  reservoir  will  always  be 
emitted  last,  and  take  the  uppermost  place  on  the  exterior  of  the  earth's 
crust. 

Test  by  included  fragments. — We  may  sometimes  discover  the  rela- 
tive age  of  two  trap  rocks,  or  of  an  aqueous  deposit  and  the  trap  on  which 
it  rests,  by  finding  fragments  of  one  included  in  the  other,  in  cases  such 
as  those  before  alluded  to,  where  the  evidence  of  superposition  alone 
would  be  insufficient.  It  is  also  not  uncommon  to  find  a  conglomerate 
almost  exclusively  composed  of  rolled  pebbles  of  trap,  associated  with 
some  fossiliferous  stratified  formation  in  the  neighborhood  of  massive 
trap.  If  the  pebbles  agree  generally  in  mineral  character  with  the 
latter,  we  are  then  enabled  to  determine  its  relative  age  by  knowing 
that  of  the  fossiliferous  strata  associated  with  the  conglomerate.  The 


CH.  XXX.]  POST-PLIOCENE  VOLCANIC  ROCKS.  523 

origin  of  such  conglomerates  is  explained  by  observing  the  shingle 
beaches  composed  of  trap  pebbles  in  modern  volcanic  islands,  or  at  the 
base  of  Etna. 

Post-Pliocene  Period  (including  the  Recent). — I  shall  now  select 
examples  of  contemporaneous  volcanic  rocks  of  successive  geological 
periods,  to  show  that  igneous  causes  have  been  in  activity  in  all  past 
ages  of  the  world,  and  that  they  have  been  ever  shifting  the  places 
where  they  have  broken  out  at  the  earth's  surface. 

One  portion  of  the  lavas,  tuffs,  and  trap-dikes  of  Etna,  Vesuvius, 
and  the  Island  of  Ischia,  has  been  produced  within  the  historical  era  j 
another,  and  a  far  more  considerable  part,  originated  at  times  immedi- 
ately antecedent,  when  the  waters  of  the  Mediterranean  were  already 
inhabited  by  the  existing  species  of  testacea.  The  southern  and  eastern 
flanks  of  Etna  are  skirted  by  a  fringe  of  alternating  sedimentary  and 
volcanic  deposits,  of  submarine  origin,  as  at  Aderno,  Trezza,  and  other 
places.  Of  sixty-five  species  of  fossil  shells  which  I  procured  in  1828 
from  this  formation,  near  Trezza,  it  was  impossible  to  distinguish  any 
one  from  species  now  living  in  the  neighbouring  sea. 

The  Cyclopian  Islands,  called  by  the  Sicilians  Dei  Faraglioni,  in  the 
sea-cliffs  of  which  these  beds  of  clay,  tuff,  and  associated  lava  are  laid 
open  to  view,  are  situated  in  the  Bay  of  Trezza,  and  may  be  regarded 

Fig.  660. 


View  of  the  Isle  of  Cyclops,  in  the  Bay  of  Trezza.* 

as  the  extremity  of  a  promontory  severed  from  the  main  land.  Here 
numerous  proofs  are  seen  of  submarine  eruptions,  by  which  the  argilla- 
ceous and  sandy  strata  were  invaded  and  cut  through,  and  tufaceous 
breccias  formed.  Inclosed  in  these  breccias  are  many  angular  and  har- 
dened fragments  of  laminated  clay  in  different  states  of  alteration  by  heat, 
and  intermixed  with  volcanic  sands. 

The  loftiest  of  the  Cyclopian  islets,  or  rather  rocks,  is  about  200  feet 
in  height,  the  summit  being  formed  of  a  mass  of  stratified  clay,  the 
laminae  of  which  are  occasionally  subdivided  by  thin  arenaceous  layers. 

*  This  yiew  of  the  Isle  of  Cyclops  is  from  an  original  drawing  by  my  friend 
the  late  Capt.  Basil  Hall,  R.  N. 


524 


VOLCANIC  KOCKS  OF 


[Cn.  XXX. 


These  strata  dip  to  the  K.  W.,  and  rest  on  a  mass  of  columnar  lava  (see 
fig.  660),  in  which  the  tops  of  the  pillars  are  weathered,  and  so  rounded 
as  to  be  often  hemispherical.  In  some  places  in  the  adjoining  and  largest 
islet  of  the  group,  which  lies  to  the  north-eastward  of  that  represented 
in  the  drawing  (fig.  660),  the  overlying  clay  has  been  greatly  altered, 
and  hardened  by  the  igneous  rock,  and  occasionally  contorted  in  the 
most  extraordinary  manner ;  yet  the  lamination  has  not  been  obliterated, 
but,  on  the  contrary,  rendered  much  more  conspicuous,  by  the  indurat- 
ing process. 

In  the  annexed  woodcut  (fig.  661)  I  have  represented  a  portion  of 
the  altered  rock,  a  few  feet  square,  where  the  alternating  thin  laminge 
n^  6C1  of  sand  and  clay  have  put  on 

the  appearance  which  we  often 
observe  in  some  of  the  most 
contorted  of  the  metamorphic 
schists. 

A  great  fissure,  running  from 
east  to  west,  nearly  divides  this 
larger  island  into  two  partgj  and 
lays  open  its  internal  structure. 
In  the  section  thus  exhibited,  a 
dike  of  lava  is  seen,  first  cutting 
through  an  older  mass  of  lava, 
and  then  penetrating  the  super- 
incumbent tertiary  strata.  In 
one  place  the  lava  ramifies  and 
terminates  in  thin  veins,  from  a 
few  feet  to  a  few  inches  in 
thickness.  (See  fig.  662.) 

The  arenaceous  laminae  are 
much  hardened  at  the  point  of 
contact,  and  the  clays  are  con- 
verted into  siliceous  schist.  In 
this  island  the  altered  rocks  as- 

Contortions  of  strata  in  the  largest  of  the  Cyclopian     SUme    a   honeycombed    structure 

on  their  weathered  surface,  sin- 
gularly contrasted  with  the  smooth  and  even  outline  which  the  same 
beds  present  in  their  usual  soft  and  yielding  state. 

The  pores  of  the  lava  are  sometimes  coated,  or  entirely  filled  with 
carbonate  of  lime,  and  with  a  zeolite  resembling  analcime,  which  has 
been  called  cyclopite.  The  latter  mineral  has  also  been  found  in  small 
fissures  traversing  the  altered  marl,  showing  that  the  same  cause  which 
introduced  the  minerals  into  the  cavities  of  the  lava,  whether  we  sup- 
pose sublimation  or  aqueous  infiltration,  conveyed  it  also  into  the  open 
rents  of  the  contiguous  sedimentary  strata. 

Post- Pliocene  formations  near  Naples. — I  have  traced  in  the  "Prin- 
ciples of  Geology"  the  history  of  the  changes  which  the  volcanic  region 


CH.  XXX.  1 


THE    POST-PLIOCENE    PERIOD. 
Fig.  662. 


525 


Clay.    Lara. 
6.  a. 


Clay. 


Lava. 


Altered. 

c. 

Post-Pliocene  strata  inyaded  by  laya,  Isle  of  Cyclops  (horizontal  section). 
a.  Lava.  6.  Laminated  clay  and  sand.  c.  The  same  altered. 


of  Campania  is  known  to  have  undergone  during  the  last  2000  years. 
The  aggregate  effect  of  igneous  operations  during  that  period  is  far 
from  insignificant,  comprising  as  it  does  the  formation  of  the  modern 
cone  of  Vesuvius  since  the  year  79,  and  the  production  of  several  minor 
cones  in  Ischia,  together  with  that  of  Monte  Nuovo  in  the  year  1538. 
Lava-currents  have  also  flowed  upon  the  land  and  along  the  bottom  of 
the  sea  —  volcanic  sand,  pumice,  and  scoriae  have  been  showered  down 
so  abundantly,  that  whole  cities  were  buried  —  tracts  of  the  sea  have 
been  filled  up  or  converted  into  shoals  —  and  tufaceous  sediment  has 
been  transported  by  rivers  and  land-floods  to  the  sea.  There  are  also 
proofs,  during  the  same  recent  period,  of  a  permanent  alteration  of  the 
relative  levels  of  the  land  and  sea  in  several  places,  and  of  the  same 
tract  having,  near  Puzzuoli,  been  alternately  upheaved  and  depressed  to 
the  amount  of  more  than  20  feet.  In  connection  with  these  convul- 
sions, there  are  found,  on  the  shores  of  the  Bay  of  Baiee,  recent  tufa- 
ceous strata,  filled  with  articles  fabricated  by  the  hands  of  man,  and 
mingled  with  marine  shells. 

It  was  also  stated  in  this  work  (p.  119),  that  when  we  examine  this 
same  region,  it  is  found  to  consist  largely  of  tufaceous  strata,  of  a  date 
anterior  to  human  history  or  tradition,  which  are  of  such  thickness  as 
to  constitute  hills  from  500  to  more  than  2000  feet  in  height.  These 
post-pliocene  strata,  containing  recent  marine  shells,  alternate  with  dis- 
tinct currents  and  sheets  of  lava  which  were  of  contemporaneous  origin ; 
and  we  find  that  in  Vesuvius  itself,  the  ancient  co&e  called  Somma  is  of 
far  greater  volume  than  the  modern  cone,  and  is  intersected  by  a  far 
greater  number  of  dikes.  In  contrasting  this  ancient  part  of  the  moun- 
tain with  that  of  modern  date,  one  principal  point  of  difference  is  ob- 
served ;  namely,  the  greater  frequency  in  the  older  cone  of  fragments 


526  VOLCANIC  EOCKS  OF  [Ca  X3X. 

of  altered  sedimentary  rocks  ejected  during  eruptions.  We  may  easily 
conceive  that  the  first  explosions  would  act  with  the  greatest  violence; 
rending  and  shattering  whatever  solid  masses  obstructed  the  escape  of 
lava  and  the  accompanying  gases,  so  that  great  heaps  of  ejected  pieces 
of  rock  would  naturally  occur  in  the  tufaceous  breccias  formed  by  the 
earliest  eruptions.  But  when  a  passage  had  once  been  opened,  and  an 
habitual  vent  established,  the  materials  thrown  out  would  consist  of 
liquid  lava,  which  would  take  the  form  of  sand  and  scoriae,  or  of  angu- 
lar fragments  of  such  solid  lavas  as  may  have  choked  up  the  vent. 

Among  the  fragments  which  abound  in  the  tufaceous  breccias  of 
Somma,  none  are  more  common  than  a  saccharoid  dolomite,  supposed 
to  have  been  derived  from  an  ordinary  limestone  altered  by  heat  and 
volcanic  vapours. 

Carbonate  of  lime  enters  into  the  composition  of  so  many  of  the 
simple  minerals  found  in  Somma,  that  M.  Mitscherlich,  with  much  pro- 
bability, ascribes  their  great  variety  to  the  action  of  the  volcanic  heat 
on  subjacent  masses  of  limestone. 

Dikes  of  Somma.  —  The  dikes  seen  in  the  great  escarpment  which 
Somma  presents  towards  the  modern  cone  of  Vesuvius  are  very  nume- 
rous. They  are  for  the  most  part  vertical,  and  traverse  at  right  angles 
the  beds  of  lava,  scoriae,  volcanic  breccia,  and  sand,  of  which  the  ancient 
cone  is  composed.  They  project  in  relief  several  inches,  or  sometimes 
feet,  from  the  face  of  the  cliff,  being  extremely  compact,  and  less  de- 
structible than  the  intersected  tuffs  and  porous  lavas.  In  vertical  extent 
they  vary  from  a  few  yards  to  500  feet,  and  in  breadth  from  1  to  12  feet. 
Many  of  them  cut  all  the  inclined  beds  in  the  escarpment  of  Somma 
from  top  to  bottom,  others  stop  short  before  they  ascend  above  half  way, 
and  a  few  terminate  at  both  ends,  either  in  a  point  or  abruptly.  In 
mineral  composition  they  scarcely  differ  from  the  lavas  of  Somma,  the 
rock  consisting  of  a  base  of  leucite  and  augite,  through  which  large 
crystals  of  augite  and  some  of  leucite  are  scattered.*  Examples  are  not 
rare  of  one  dike  cutting  through  another,  and  in  one  instance  a  shift  or 
fault  is  seen  at  the  point  of  intersection. 

In  some  cases,  however,  the  rents  seem  to  have  been  filled  laterally, 
when  the  walls  of  the  crater  had  been  broken  by  star-shaped  cracks,  as 
seen  in  the  accompanying  wood-cut  (fig.  663).  But  the  shape  of  these 
rents  is  an  exception  to  the  general  rule ;  for  nothing  is  more  remarka- 
ble than  the  usual  parallelism  of  the  opposite  sides  of  the  dikes,  which 
correspond  almost  as  regularly  as  the  two  opposite  faces  of  a  wall  of 
masonry.  This  character  appears  at  first  the  more  inexplicable,  when 
we  consider  how  jagged  and  uneven  are  the  rents  caused  by  earthquakes 
in  masses  of  heterogeneous  composition,  like  those  composing  the  cone 
of  Somma.  In  explanation  of  this  phenomenon,  M.  Necker  refers  us 
to  Sir  W.  Hamilton's  account  of  an  eruption  of  Vesuvius  in  the  year 

*.  L.  A.  decker,  Mem.  de  la  Soc.  de  Phys.  et  d'Hist.  Nat.  de  G6n£ve,  torn.  ii. 
part  i.  Nov.  1822. 


CH.  XXX.' 


THE   POST-PLIOCENE   PERIOD. 


Fig.  663. 


527 


Dikes  or  reins  at  the  Punto  del  Naaone  on  Somma.    (Necker.*) 

1779,  who  records  the  following  facts :  —  "  The  lavas,  when  they  either 
boiled  over  the  crater,  or  broke  out  from  the  conical  parts  of  the  volcano, 
constantly  formed  channels  as  regular  as  if  they  had  been  cut  by  art 
down  the  steep  part  of  the  mountain ;  and,  whilst  in  a  state  of  perfect 
fusion,  continued  their  course  in  those  channels,  which  were  sometimes 
full  to  the  brim,  and  at  other  times  more  or  less  so,  according  to  the 
quantity  of  matter  in  motion. 

u  These  channels,  upon  examination  after  an  eruption,  I  have  found 
to  be  in  general  from  two  to  five  or  six  feet  wide,  and  seven  or  eight 
feet  deep.  They  were  often  hid  from  the  sight  by  a  quantity  of  scoriae 
that  had  formed  a  crust  over  them ;  and  the  lava,  having  been  conveyed 
in  a  covered  way  for  some  yards,  came  out  fresh  again  into  an  open  chan- 
nel. After  an  eruption,  I  have  walked  in  some  of  those  subterraneous 
or  covered  galleries,  which  were  exceedingly  curious,  the  sides,  top,  and 
bottom  being  worn  perfectly  smooth  and  even  in  most  parts,  by  the  vio- 
lence of  the  currents  of  the  red-hot  lavas  which  they  had  conveyed  for 
many  weeks  successively,  "f 

Now,  the  walls  of  a  vertical  fissure,  through  which  lava  has  ascended 
in  its  way  to  a  volcanic  vent,  must  have  been  exposed  to  the  same  ero- 
sion as  the  sides  of  the  channels  before  adverted  to.  The  prolonged  and 
uniform  friction  of  the  heavy  fluid,  as  it  is  forced  and  made  to  flow  up- 
wards, cannot  fail  to  wear  and  smooth  down  the  surfaces  on  which  it 
rubs,  and  the  intense  heat  must  melt  all  such  masses  as  project  and 
obstruct  the  passage  of  the  incandescent  fluid. 

The  texture  of  the  Vesuvian  dikes  is  different  at  the  edges  and  in  the 
middle.  Towards  the  centre,  observes  M.  Necker,  the  rock  is  larger 
grained,  the  component  elements  being  in  a  far  more  ciystalline  state ; 
while  at  the  edge  the  lava  is  somewhat  vitreous,  and  always  finer  grained. 
A  thin  parting  band,  approaching  in  its  character  to  pitchstone,  occasion- 

*  From  a  drawing  of  M.  Necker,  in  Mem.  above  cited, 
f  PhiL  Trans,  vol.  Ixx.  1780. 


528  POST-PLIOCENE  VOLCANIC  EOCKS.  [On.  XXX. 

ally  intervenes,  on  the  contact  of  the  vertical  dike  and  intersected  beds. 
M.  Necker  mentions  one  of  these  at  the  place  called  Primo  Monte,  in  the 
Atrio  del  Cavallo  ;  and  when  I  examined  Somma,  in  1828, 1  saw  three 
or  four  others  in  different  parts  of  the  great  escarpment.  These  phenom- 
ena are  in  perfect  harmony  with  the  results  of  the  experiments  of  Sir 
James  Hall  and  Mr.  Gregory  Watt,  which  have  shown  that  a  glassy  tex- 
ture is  the  effect  of  sudden  cooling,  while,  on  the  contrary,  a  crystalline 
grain  is  produced  where  fused  minerals  are  allowed  to  consolidate  slowly 
and  tranquilly  under  high  pressure. 

It  is  evident  that  the  central  portion  of  the  lava  in  a  fissure  would, 
during  consolidation,  part  with  its  heat  more  slowly  than  the  sides, 
although  the  contrast  of  circumstances  would  not  be  so  great  as  when  we 
compare  the  lava  near  the  bottom  and  at  the  surface  of  a  current  flow- 
ing in  the  open  air.  In  this  case  the  uppermost  part,  where  it  has  been 
in  contact  with  the  atmosphere,  and  where  refrigeration  has  been  most 
rapid,  is  always  found  to  consist  of  scoriform,  vitreous,  and  porous  lava ; 
while  at  a  greater  depth  the  mass  assumes  a  more  lithoidal  structure, 
and  then  becomes  more  and  more  stony  as  we  descend,  until  at  length 
we  are  able  to  recognize  with  a  magnifying  glass  the  simple  minerals  of 
which  the  rock  is  composed.  On  penetrating  still  deeper,  we  can  detect 
the  constituent  parts  by  the  naked  eye,  and  in  the  Vesuvian  currents 
distinct  crystals  of  augite  and  leucite  become  apparent. 

The  same  phenomenon,  observes  M.  Necker,  may  readily  be  exhibited 
on  a  smaller  scale,  if  we  detach  a  piece  of  liquid  lava  from  a  moving 
current.  The  fragment  cools  instantly,  and  we  find  the  surface  covered 
with  a  vitreous  coat ;  while  the  interior,  although  extremely  fine-grained, 
has  a  more  stony  appearance. 

It  must,  however,  be  observed,  that  although  the  lateral  portions  of 
the  dikes  are  finer  grained  than  the  central,  yet  the  vitreous  parting 
layer  before  alluded  to  is  rare  in  Vesuvius.  This  may,  perhaps,  be 
accounted  for,  as  the  above-mentioned  author  suggests,  by  the  great  heat 
which  the  walls  of  a  fissure  may  acquire  before  the  fluid  mass  begins  to 
consolidate,  in  which  case  the  lava,  even  at  the  sides,  would  cool  very 
slowly.  Some  fissures,  also,  may  be  filled  from  above,  as  frequently 
happens  in  the  volcanos  of  the  Sandwich  Islands,  according  to  the  obser- 
vations of  Mr.  Dana;  and  in  this  case  the  refrigeration  at  the  sides 
would  be  more  rapid  than  when  the  melted  matter  flowed  upwards  from 
the  volcanic  foci,  in  an  intensely  heated  state.  Mr.  Darwin  informs  me 
that  in  St.  Helena  almost  every  dike  has  a  vitreous  selvage. 

The  rock  composing  the  dikes  both  in  the  modern  and  ancient  part  of 
Vesuvius  is  far  more  compact  than  that  of  ordinary  lava,  for  the  pres- 
sure of  a  column  of  melted  matter  in  a  fissure  greatly  exceeds  that  in 
an  ordinary  stream  of  lava;  and  pressure  checks  the  expansion  of  those 
gases  which  give  rise  to  vesicles  in  lava. 

There  is  a  tendency  in  almost  all  the  Vesuvian  dikes  to  divide  into 
horizontal  prisms,  a  phenomenon  in  accordance  with  the  formation  of 
vertical  columns  in  horizontal  beds  of  lava ;  for  in  both  cases  the  divi- 


CH.  XXX.]  NEWER  PLIOCENE  VOLCANIC  ROCKS. 


529 


sions  which  give  rise  to  the  prismatic  structure  are  at  right  angles  to  the 
cooling  surfaces. 

Newer  Pliocene  Period  —  Val  di  Noto.  —  I  have  already  alluded  (see 
p.  156)  to  the  igneous  rocks  which  are  associated  with  a  great  marine 
formation  of  limestone,  sand,  and  marl,  in  the  southern  part  of  Sicily, 
as  at  Vizzini  and  other  places.  In  this  formation,  which  was  shown  to 
belong  to  the  Newer  Pliocene  period,  large  beds  of  oysters  and  corals 
repose  upon  lava,  and  are  unaltered  at  the  point  of  contact.  In  other 
places  we  find  dikes  of  igneous  rock  intersecting  the  fossiliferous  beds, 
and  converting  the  clays  into  siliceous  schist,  the  laminae  being  contorted 
and  shivered  into  innumerable  fragments  at  the  junction,  as  near  the 
town  of  Vizzini. 

The  volcanic  formations  of  the  Val  di  Noto  usually  consist  of  the 
most  ordinary  variety  of  basalt,  with  or  without  olivine.  The  rock  is 
sometimes  compact,  often  very  vesicular.  The  vesicles  are  occasionally 
empty,  both  in  dikes  and  currents,  and  are  in  some  localities  filled  with 
calcareous  spar,  arragonite,  and  zeolites.  The  structure  is,  in  some 
places,  spheroidal  j  in  others,  though  rarely,  columnar.  I  found  dikes 
of  amygdaloid,  wacke,  and  prismatic  basalt,  intersecting  the  limestone 
at  the  bottom  of  the  hollow  called  Gozzo  degli  Martiri,  below  Melilli. 

Dikes.  —  Dikes  of  vesicular  and  amygdaloidal  lava  are  also  seen  tra- 
versing marine  tuff  or  peperino,  west  of  Palagonia,  some  of  the  pores 
of  the  lava  being  empty,  while  others  are  filled  with  carbonate  of  lime 

Fig.  664. 


Ground-plan  of  dikes  near  Palagonia. 
a.  Lara. 

6.  Peperino,  consisting  of  rolcanic  sand,  mixed  with 
fragments  of  lava  and  limestone. 

In  such  cases,  we  may  suppose  the  peperino  to  have  resulted  from 
showers  of  volcanic  sand  and  scoriae,  together  with  fragments  of  lime- 
stone, thrown  out  by  a  submarine  explosion,  similar  to  that  which  gave 
rise  to  Graham  Island  in  1831.  When  the  mass  was,  to  a  certain 
degree,  consolidated,  it  may  have  been  rent  open,  so  that  the  lava 
ascended  through  fissures,  the  walls  of  which  were  perfectly  even  and 
parallel.  After  the  melted  matter  that  filled  the  rent  in  fig.  664,  had 
cooled  down,  it  must  have  been  fractured  and  shifted  horizontally  by  a 
lateral  movement 

In  the  second  figure  (fig.  665),  the  lava  has  more  the  appearance  of  a 
vein  which  forced  its  way  through  the  peperino.     It  is  highly  probable 

34 


530  PLIOCENE  VOLCANOS.  [On.  XXXI. 

that  similar  appearances  would  be  seen,  if  we  could  examine  the  floor 
of  the  sea  in  that  part  of  the  Mediterranean  where  the  waves  have 
recently  washed  away  the  new  volcanic  island ;  for  when  a  superincum- 
bent mass  of  ejected  fragments  has  been  removed  by  denudation,  we 
may  expect  to  see  sections  of  dikes  traversing  tuff,  or  in  other  words, 
sections  of  the  channels  of  communication  by  which  the  subterranean 
lavas  reached  the  surface. 


CHAPTER  XXXI. 

ON   THE   DIFFERENT   AGES   OF   THE   VOLCANIC   ROCKS  —  continued. 

Volcanic  rocks  of  the  Older  Pliocene  period — Tuscany — Home— Volcanic  region 
of  Olot  in  Catalonia — Cones  and  lava-currents  —  Eavines  and  ancient  gravel- 
beds — Jets  of  air  called  Bufadors — Age  of  the  Catalonian  volcanos — Miocene 
period  —  Brown  coal  of  the  Eifel  and  contemporaneous  trachytic  breccias  — 
Age  of  the  brown-coal — Peculiar  characters  of  the  volcanos  of  the  upper  and 
lower  Eifel  —  Lake  craters  —  Trass  —  Hungarian  volcanos. 

Older  Pliocene  Period — Italy. — IN  Tuscany,  as  at  Radicofani,  Viterbo, 
and  Aquapendente,  and  in  the  Campagna  di  Roma,  submarine  volcanic 
tuffs  are  interstratified  with  the  Older  Pliocene  strata  of  the  Subapennine 
hills,  in  such  a  manner  as  to  leave  no  doubt  that  they  were  the  products 
of  eruptions  which  occurred  when  the  shelly  marls  and  sands  of  the  Sub- 
apennine hills  were  in  the  course  of  deposition.  This  opinion  I  expressed* 
after  my  visit  to  Italy  in  1828,  and  it  has  recently  (1850)  been  confirmed 
by  the  arguments  adduced  by  Sir  R.  Murchison  in  favor  of  the  submarine 
origin  of  the  earlier  volcanic  rocks  of  Italy .f  These  rocks  are  well  known 
to  rest  conformably  on  the  Subapennine  marls,  even  as  far  south  as  Monte 
Mario  in  the  suburbs  of  Rome.  On  the  exact  age  of  the  deposits  of  Monte 
Mario  new  light  has  recently  been  thrown  by  a  careful  study  of  their 
marine  fossil  shells,  undertaken  by  MM.  Rayneval,  Vanden  Hecke,  and 
Ponza.  They  have  compared  no  less  than  160  species^  with  the  shells  of 
the  Coralline  Crag  of  Suffolk,  so  well  described  by  Mr.  Searles  Wood  ; 
and  the  specific  agreement  between  the  British  and  Italian  fossils  is  so 
great,  if  we  make  due  allowance  for  geographical  distance  and  the  differ- 
ence of  latitude,  that  we  can  have  little  hesitation  in  referring  both  to  the 
same  period  or  to  the  Older  Pliocene  of  this  work.  It  is  highly  probable 
that,  between  the  oldest  trachytes  of  Tuscany  and  the  newest  rocks  in  the 

*  See  1st  edit,  of  Principles  of  Geology,  vol.  iii.  chaps,  xiii.  and  xiv.  1833;  and 
former  edits,  of  this  work,  ch.  XXXL 
f  Geol.  Quart.  Journ.  vol.  vi.  p.  281. 
j  Catalogue  des  Fossiles  de  Monte  Mario,  Rome,  1854. 


Or.  XXXI.] 


VOLCANOS  OF  CATALONIA. 


531 


neighborhood  of  Naples,  a  series  of  volcanic  products  might  be  detected 
of  every  age  from  the  Older  Pliocene  to  the  historical  epoch. 

Catalonia. — Geologists  are  far  from  being  able,  as  yet,  to  assign  to 
each  of  the  volcanio  groups  scattered  over  Europe  a  precise  geological 
place  in  the  tertiary  series ;  but  I  shall  describe  here,  as  probably  refer- 
able to  some  part  of  the  Pliocene  period,  a  district  of  extinct  volcanos 
near  Olot,  in  the  north  of  Spain,  which  is  little  known,  and  which  I  visited 
in  the  summer  of  1830. 

The  whole  extent  of  country  occupied  by  volcanic  products  in  Cata- 
lonia is  not  more  than  fifteen  geographical  miles  from  north  to  south,  and 
about  six  from  east  to  west  The  vents  of  eruption  range  entirely  within 
a  narrow  band  running  north  and  south ;  and  the  branches,  which  are 
represented  as  extending  eastward  in  the  map,  are  formed  simply  of  two 
lava-streams — those  of  Castell  Follit  and  Cellent. 


Fig.  666. 


Volcanic  district  of  Catalonia. 

Dr.  MacClure,  the  American  geologist,  was  the  first  who  made  known 
the  existence  of  these  volcanos  ;*  and,  according  to  his  description,  the 
volcanic  region  extended  over  twenty  square  leagues,  from  Amer  to 
Massanet.  I  searched  in  vain  in  the  environs  of  Massanet,  in  the  Pyre- 
nees, for  traces  of  a  lava-current;  and  I  can  say,  with  confidence,  that 

*  Maclure,  Journ.  de  Phys.,  vol.  Ixvi.  p.  213,  1808;  cited  by  Daubeny,  De 
scription  of  Volcanos,  p.  24. 


532  VOLCANOS  OF   CATALONIA.'  [On.  XXXI. 

the  adjoining  map  gives  a  correct  view  of  the  true  area  of  the  volcanic- 
action. 

Geological  structure  of  the  district. — The  eruptions  have  burst  entirely 
through  fossiliferous  rocks,  composed  in  great  part  of  gray  and  greenish 
sandstone  and  conglomerate,  with  some  thick  beds  of  nurnmulitic  lime- 
stone. The  conglomerate  contains  pebbles  of  quartz,  limestone,  and 
Lydian  stone.  This  system  of  rocks  is  very  extensively  spread  throughout 
Catalonia  ;  one  of  its  members  being  a  red  sandstone,  to  whi«h  the  cele- 
brated salt-rock  of  Cardona,  usually  considered  as  of  the  cretaceous  era, 
is  subordinate. 

Near  Amer,  in  the  Valley  of  the  Ter,  on  the  southern  borders  of  the 
region  delineated  in  the  map,  primary  rocks  are  seen,  consisting  of  gneiss, 
mica-schist,  and  clay-slate.  They  run  in  a  line  nearly  parallel  to  the 
Pyrenees,  and  throw  off  the  fossiliferous  strata  from  their  'Janks,  causing 
them  to  dip  to  the  north  and  northwest.  This  dip,  which  is  towards 
the  Pyrenees,  is  connected  with  a  distinct  axis  of  elevatioa,  and  pre- 
vails through  the  whole  area  described  in  the  map,  the  inclination  of 
the  beds  being  sometimes  at  an  angle  of  between  40  and  50  degrees. 

It  is  evident  that  the  physical  geography  of  the  country  has  under- 
gone no  material  change  since  the  commencement  of  the  era  of  the 
volcanic  eruptions,  except  such  as  has  resulted  from  the  introduction  of 
new  hills  of  scoriae,  and  currents  of  lava  upon  the  surface.  If  the  lavas 
could  be  remelted  and  poured  out  again  from  their  respective  craters, 
they  would  descend  the  same  valleys  in  which  they  are  now  seen,  and 
re-occupy  the  spaces  which  they  at  present  fill.  The  only  difference  in 
the  external  configuration  of  the  fresh  lavas  would  consist  in  this,  that 
they  would  nowhere  be  intersected  by  ravines,  or  exhibit  marks  of  ero- 
sion by  running  water. 

Fig.  667. 


View  of  the  Volcanos  around  Olot  in  Catalonia. 


CH.  XXXI.]  •   PLIOCENE  YOLCAXOS.  533 

Volcanic  cones  and  lavas. — There  are  about  fourteen  distinct  cones 
with  craters  in  this  part  of  Spain,  besides  several  points  whence  lavas 
may  have  issued ;  all  of  them  arranged  along  a  narrow  line  running 
north  and  south,  as  will  be  seen  in  the  map.  The  greatest  number  of 
perfect  cones  are  in  the  immediate  neighborhood  of  Clot,  some  of  which 
(fig.  667,  Nos.  2,  3,  and  5)  are  represented  in  the  above  drawing ;  and 
the  level  plain  on  which  that  town  stands  has  clearly  been  produced  by 
the  flowing  down  of  many  lava-streams  from  those  hills  into  the  bottom 
of  a  valley,  probably  once  of  considerable  depth,  like  those  of  the  sur- 
rounding country. 

In  the  above  drawing  an  attempt  is  made  to  represent,  by  the  shading 
of  the  landscape,  the  different  geological  formations  of  which  the  country 
is  composed.*  The  white  line  of  mountains  (No.  1)  in  the  distance  is 
the  Pyrenees,  which  are  to  the  north  of  the  spectator,  and  consist  of  hy- 
pogene  and  ancient  fossiliferous  rocks.  In  front  of  these  are  the  fossilifer- 
ous  formations  (No.  4)  which  are  in  shade.  Still  nearer  to  us,  the  hills 
2,  3,  5  are  volcanic  cones,  and  the  rest  o%the  ground  on  which  the  sun- 
shine falls  is  strewed  over  with  volcanic  ashes  and  lava. 

The  Fluvia,  which  flows  near  the  town  of  Olot,  has  cut  to  the  depth 
of  only  40  feet  through  the  lavas  of  the  plain  before  mentioned.  The 
bed  of  the  river  is  hard  basalt ;  and  at  the  bridge  qf  Santa  Madalena  are 
seen  two  distinct  lava-currents,  one  above  the  other,  separated  by  a  hori- 
zontal bed  of  scoriae  8  feet  thick. 

In  one  place,  to  the  south  of  Olot,  the  even  surface  of  the  plain  is 
broken  by  a  mound  of  lava,  called  the  "  Bosque  de  Tosca,"  the  upper 
part  of  which  is  scoriaceous,  and  covered  with  enormous  heaps  of  frag- 
ments of  basalt,  more  or  less  porous.  Between  the  numerous  hummocks 
thus  formed  are  deep  cavities,  having  the  appearance  of  small  craters. 
The  whole  precisely  resembles  some  of  the  modern  currents  of  Etna,  or 
that  of  Come,  near  Clermont;  the  last  of  which,  like  the  Bosque  de 
Tosca,  supports  only  a  scanty  vegetation. 

Most  of  the  Catalonian  volcanoes  are  as  entire  as  those  in  the  neigh- 
borhood of  Naples,  or  on  the  flanks  of  Etna.  One  of  these,  called 
Montsacopa  (No.  3,  fig.  667),  is  of  a  very  regular  form,  and  has  a  cir- 
cular depression  or  crater  at  the  summit  It  is  chiefly  made  up  of 
red  scoriae,  undistinguishable  from  those  of  minor  cones  of  Etna.  The 
neighboring  hills  of  Olivet  (No.  2)  and  Garrinada  (No.  5)  are  of  simi- 
lar composition  and  shape.  The  largest  crater  of  the  whole  district 
occurs  farther  to  the  east  of  Olot,  and  is  called  Santa  Margarita.  It  is 
455  feet  deep,  and  about  a  mile  in  circumference.  Like  Astroni,  near 
Naples,  it  is  richly  covered  with  wood,  wherein  game  of  various  kinds 
abounds. 

Although  the  volcanos  of  Catalonia  have  broken  out  through  sand 
stone,  shale,  and  limestone,  as  have  those  of  the  Eifel,  in  Germany,  to 
DA  described  in  the  sequel,  there  is  a  remarkable  difference  in  the  nature 

*  This  view  is  taken  from  a  sketch  which  I  made  on  the  spot  in  1839. 


534:  PLIOCENE  YOLCANOS.      *  [Cn.  XXXI. 

of  the  ejections  composing  the  cones  in  these  two  regions.  In  the  Eifel, 
the  quantity  of  pieces  of  sandstone  and  shale  thrown  out  from  the  vents 
is  often  so  immense  as  far  to  exceed  in  volume  the  scoriae,  pumice,  and 
lava ;  but  I  sought  in  vain  in  the  cones  near  Olot  for  a  single  fragment 
of  any  extraneous  rock ;  and  Don  Francisco  Bolos,  an  eminet  botanist 
of  Olot,  informed  me  that  he  had  never  been  able  to  detect  any.  Vol- 
Fig  668  canic  sand  and  ashes  are  not  confined 

to  the  cones,  but  have  been  some- 
times scattered  by  the  wind  over  the 
country,  and  drifted  into  narrow  val- 
leys, as  is  seen  between  Olot  and 
Cellent,  where  the  annexed  section 
(fig.  668)  is  exposed.  The  light 


a.  Secondary  conglomerate.  cindery  volcanic  matter  rests  in  thin 

p.  Thin  seams  of  volcanic  sand  and  scoriae.  .  *  _ 

regular  layers,  just  as  it  alighted  on 

the  slope  formed  by  the  solid  conglomerate.  No  flood  could  have  passed 
through  the  valley  since  the  storiae  fell,  or  these  would  have  been  for 
the  most  part  removed. 

The  currents  of  lava  in  Catalonia,  like  those  of  Auvergne,  the  Viva- 
rais,  Iceland,  and  all  mountainous  countries,  are  of  considerable  depth  in 
narrow  defiles,  but  spread  out  into  comparatively  thin  sheets  in  places 
where  the  valleys  widen.  If  a  river  has  flowed  on  nearly  level  ground, 
as  in  the  great  plain  near  Olot,  the  water  has  only  excavated  a  channel 
of  slight  depth ;  but  where  the  declivity  is  great,  the  stream  has  cut  a 
deep  section,  sometimes  by  penetrating  directly  through  the  central  part 
of  a  lava-current,  but  more  frequently  by  passing  between  the  lava  and 
the  secondary  or  tertiary  rock  which  bounds  the  valley.  Thus,  in  the 
accompanying  section,  fig.  669,  at  the  bridge  of  Cellent,  six  miles  east  of 
Olot,  we  see  the  lava  on  one  side  of  the  small  stream  ;  while  the  inclined 
stratified  rocks  constitute  the  channel  and  opposite  bank.  The  upper  part 
of  the  lava  at  that  place,  as  is  usual  in  the  currents  of  Etna  and  Vesuvius, 
is  scoriaceous ;  farther  down  it  becomes  less  porous,  and  assumes  a  sphe- 
roidal structure ;  still  lower  it  divides  in  horizontal  plates,  each  about  2 
inches  in  thickness,  and  is  more  compact.  Lastly,  at  the  bottom  is  a 
mass  of  prismatic  basalt  about  five  feet  thick.  The  vertical  columns  often 
rest  immediately  on  the  subjacent  stratified  rocks ;  but  there  is  sometimes 
an  intervention  of  sand  and  scoriae  such  as  cover  the  country  during  vol- 
canic eruptions,  and  which,  unless  protected,  as  here,  by  superincumbent 
lava,  is  washed  away  from  the  surface  of  the  laud.  Sometimes,  the  bed 
d  contains  a  few  pebbles  and  angular  fragments  of  rock  ;  in  other  places 
fine  earth,  which  may  have  constituted  an  ancient  vegetable  soil. 

In  several  localities,  beds  of  sand  and  ashes  are  interposed  between 
the  lava  and  subjacent  stratified  rock,  as  may  be  seen  if  we  follow  the 
course  of  the  lava-current  which  descends  from  Las  Planas  towards 
Amer,  and  stops  two  miles  short  of  that  town.  The  river  there  has 
often  cut  through  the  lava,  and  through  18  feet  of  underlying  limestone. 
Occasionally  an  alluvium,  several  feet  thick,  is  interposed  between  the 


CH.  XXXL] 


•YOLCANOS  OF  CATALOXIA. 


535 


Fig.  669. 


Section  above  the  bridge  of  Cellent 


a.  Scoriaceous  lava. 

b.  Schistose  basalt. 

c.  Columnar  basalt. 


fl.  Scoriae,  vegetable  soil,  and  alluvium. 
«.  Nummulitic  limestone. 
j.  Micaceous  grey  sandstone. 


gneous  and  marine  formations  ;  and  it  is  interesting  to  remark  that  in 
this,  as  in  other  beds  of  pebbles  occupying  a  similar  position,  there  are 
no  rounded  fragments  of  lava  ;  whereas  in  the  most  modern  gravel-beds 
of  the  rivers  of  this  country,  volcanic  pebbles  are  abundant. 

The  deepest  excavation  made  by  a  river  through  lava,  which  I  ob- 
served in  this  part  of  Spain,  is  seen  in  the  bottom  of  a  valley  near 
San  Feliu  de  Pallerdls,  opposite  the  Castell  de  Stolles.  The  lava  there 
has  filled  up  the  bottom  of  a  valley,  and  a  narrow  ravine  has  been  cut 
through  it  to  the  depth  of  100  feet.  In  the  lower  part  the  lava  has  a 
columnar  structure.  A  great  number  of  ages  were  probably  required 
for  the  erosion  of  so  deep  a  ravine ;  but  we  have  no  reason  to  infer  that 
this  current  is  of  higher  antiquity  than  those  of  the  plain  near  Olot. 
The  fall  of  the  ground,  and  consequent  velocity  of  the  stream,  being  in 
this  case  greater,  a  more  considerable  volume  of  rock  may  have  been 
removed  in  the  same  time. 


Fig.  era 


Section  at  Castell  Follit. 

A.  Church  and  town  of  Castell  Follit,  overlooking  precipices  of  basalt. 

B.  Small  island,  on  each  side  of  which  branches  of  the  river  Teronel  flow  to  meet  the 

Fluvia, 

c.  Precipice  of  basaltic  lava,  chiefly  columnar,  about  130  feet  in  height. 

d.  Ancient  alluvium,  underlying  the  lava-current. 
c.  Inclined  strata  of  secondary  sandstone. 


530  PLIOCENE  VOLCANOS.  [On.  XXXI. 

I  shall  describe  one  more  section  to  elucidate  the  phenomena  of  this 
district.  A  lava- stream,  flowing  from  a  ridge  of  hills  on  the  east  of 
Olot,  descends  a  considerable  slope,  until  it  reaches  the  valley  of  the 
river  Fluvia.  Here,  for  the  first  time,  it  comes  in  contact  with  running 
water,  which  has  removed  a  portion,  and  laid  open  its  internal  structure 
in  a  precipice  about  180  feet  in  height,  at  the  edge  of  which  stands  the 
town  of  Castell  Follit. 

By  the  junction  of  the  rivers  Fluvia  and  Teronel  the  mass  of  lava  has 
been  cut  away  on  two  sides;  and  the  insular  rock  B  (fig.  474)' has  been 
left,  which  was  probably  never  so  high  as  the  cliff  A,  as  it  may  have  con- 
stituted the  lower  part  of  the  sloping  side  of  the  original  current. 

From  an  examination  of  the  vertical  cliffs,  it  appears  that  the  upper 
part  of  the  lava  on  which  the  town  is  built  is  scoriaceous,  passing  down- 
wards into  a  spheroidal  basalt ;  some  of  the  huge  spheroids  being  no  less 
than  6  feet  in  diameter.  Below  this  is  a  more  compact  basalt,  with  crys- 
tals of  olivine.  There  are  in  all  five  distinct  ranges  of  basalt,  the  upper- 
most spheroidal,  and  the  rest  prismatic,  separated  by  thinner  beds  not 
columnar,  and  some  of  which  are  schistose.  These  were  probably  formed 
by  successive  flows  of  lava,  whether  during  the  same  eruption  or  at  dif- 
ferent periods.  The  whole  mass  rests  on  alluvium,  ten  or  twelve  feet 
in  thickness,  composed  of  pebbles  of  limestone  and  quartz,  but  without 
any  intermixture  of  igneous  rocks;  in  which  circumstance  alone  it 
appears  to  differ  from  the  modern  gravel  of  the  Fluvia. 

Bufadors.  —  The  volcanic  rocks  near  Olot  have  often  a  cavernous 
structure,  like  some  of  the  lavas  of  Etna ;  and  in  many  parts  of  the  hill 
of  Batet,  in  the  environs  of  the  town,  the  sound  returned  by  the  earth, 
when  struck,  is  like  that  of  an  archway.  At  the  base  of  the  same  hill 
are  the  mouths  of  several  subterranean  caverns,  about  twelve  in  num- 
ber, called  in  the  country  "bufadors,"  from  which  a  current  of  cold 
air  issues  during  summer,  but  which  in  winter  is  said  to  be  scarcely 
perceptible.  I  visited  one  of  these  bufadors  in  the  beginning  of  August, 
1830,  when  the  heat  of  the  season  was  unusually  intense,  and  found  a 
cold  wind  blowing  from  it,  which  may  easily  be  explained ;  for  as  the 
external  air,  when  rarefied  by  heat,  ascends,  the  pressure  of  the  colder 
and  heavier  air  of  the  caverns  in  the  interior  of  the  mountain  causes  it 
to  rush  out  to  supply  its  place. 

In  regard  to  the  age  of  these  Spanish  volcanos,  attempts  have  been 
made  to  prove,  that  in  this  country,  as  well  as  in  Auvergne  and  the 
Eifel,  the  earliest  inhabitants  were  eye-witnesses  to  the  volcanic  action. 
In  the  year  1421,  it  is  said,  when  Olot  was  destroyed  by  an  earthquake, 
an  eruption  broke  out  near  Amer,  and  consumed  the  town.  The  re- 
searches of  Don  Francisco  Bolos  have,  I  think,  shown,  in  the  most 
satisfactory  manner,  that  there  is  no  good  historical  foundation  for  the 
latter  part  of  this  story  j  and  any  geologist  who  has  visited  Amer  must 
be  convinced  that  there  never  was  any  eruption  on  that  spot.  It  is  true 
that,  in  the  year  above  mentioned,  the  whole  of  Olot,  with  the  exception 


CH.  XXXI.]  MIOCENE  VOLCANIC  ROCKS.  537 

of  a  single  house,  was  cast  down  by  an  earthquake ;  one  of  those  shocks 
which,  at  distant  intervals  during  the  last  five  centuries,  have  shaken  the 
Pyrenees,  and  particularly  the  country  between  Perpignan  and  Olot, 
where  the  movements,  at  the  period  alluded  to,  were  most  violent. 

The  annihilation  of  the  town  may,  perhaps,  have  been  due  to  the  cav- 
ernous nature  of  the  subjacent  rocks ;  for  Catalonia  is  beyond  the  line  of 
those  European  earthquakes  which  have,  within  the  period  of  history,  de- 
stroyed towns  throughout  extensive  areas. 

As  we  have  no  historical  records,  then,  to  guide  us  in  regard  to  the 
extinct  volcanos,  we  must  appeal  to  geological  monuments.  The  annexed 
diagram,  fig.  671,  will  present  to  the  reader,  in  a  synoptical  form,  the  re- 
sults obtained  from  numerous  sections. 

The  more  modern  alluvium   (d)  is  partial,  and  has  been  formed  by 

Fig.  671. 


Superposition  of  rocks  in  the  vokanic  district  of  Catalonia. 

a.  Sandstone  and  nummulitic  limestone. 

b.  Older  alluvium  without  volcanic  pebbles. 

c.  Cones  of  scoriae  and  lava.  d.  Newer  alluvium. 

the  action  of  rivers  and  floods  upon  the  lava ;  whereas  the  older  gravel 
(£>)  was  strewed  over  the  country  before  the  volcanic  eruptions.  In 
neither  have  any  organic  remains  been  discovered ;  so  that  we  can  merely 
affirm,  as  yet,  that  the  volcacos  broke  out  after  the  elevation  of  some 
of  the  newest  rocks  of  the  nummulitic  (Eocene)  series  of  Catalonia,  and 
before  the  formation  of  an  alluvium  (d)  of  unknown  date.  The  integrity 
of  the  cones  merely  shows  that  the  country  has  not  been  agitated  by  vio- 
lent earthquakes,  or  subjected  to  the  action  of  any  great  flood  since  their 
origin. 

East  of  Olot,  on  the  Catalonian  coast,  marine  tertiary  strata  occur, 
which,  near  Barcelona,  attain  the  height  of  about  500  feet.  From  the 
shells  which  I  collected,  these  strata  appear  to  correspond  in  age  with  the 
Subapennine  beds ;  and  it  is  not  improbable  that  their  upheaval  from 
beneath  the  sea  took  place  during  the  period  of  volcanic  eruption  round 
Olot.  In  that  case  these  eruptions  may  have  occurred  at  the  close  of  the 
Older  Pliocene  era,  but  perhaps  subsequently,  for  their  age  is  at  present 
quite  uncertain. 

Volcanic  rocks  of  the  Eifel. — The  chronological  relations  of  the  vol- 
canic rocks  of  the  lower  Rhine  and  the  Eifel  are  also  involved  in  a  con- 
siderable degree  of  ambiguity  ;  but  we  know  that  some  portion  of  them 
were  coeval  with  certain  tertiary  deposits  called  "  Brown-Coal"  by  the 


538 


MIOCENE  VOLCANIC  KOCKS. 


[Cn.  XXXI. 


Germans,  which  probably  belong  in  part  to  the  Miocene,  and  in  part  to 
the  Upper  Eocene,-  epoch. 

This  JBrown-Coal  is  seen  on  both  sides  of  the  Rhine,  in  the  neighbor- 
hood of  Bonn,  resting  unconforraably  on  highly  inclined  and  vertical 
strata  of  Silurian  and  Devonian  rocks.  Its  geographical  position,  and  the 
space  occupied  by  the  volcanic  rocks,  both  of  the  Westerwald  and  Eifel, 
will  be  seen  by  referring  to  the  map  (fig.  672),  for  which  I  am  indebted 
to  Mr.  Horner,  whose  residence  for  some  years  in  the  country  enabled 
him  to  verify  the  maps  of  MM.  Noeggerath  and  Von  Oeynhausen,  from 
which  that  now  given  has  been  principally  compiled.* 

The  Brown-coal  formation  of  that  region  consists  of  beds  of  loose  sand, 
sandstone,  and  conglomerate,  clay  with  nodules  of  clay-ironstone,  and  oc- 
casionally silex.  Layers  of  light  brown,  and  sometimes  black  lignite,  are 
interstratified  with  the  clays  and  sands,  and  often  irregularly  diffused 


Fig.  672. 


Map  of  the  volcanic  region  of  the  Upper  and  Lower  Eifel. 
1234  5  English  miles. 

(•.•-:..-..-. .  |  Volcanic     J  A.  of  the  Upper  Eifel.  <    .-^  \  Points  of  eruption,  with  craters  and 

L/Sr^Sj  District       (  B.  of  the  Lower  Eifel.  \   ^^  I      scoriae. 

Trachyte. 


Basalt. 
Brown  coal. 

ZV.  B.    The  country  in  that  part  of  the  map  which  is  left  blank  is  composed  of  inclined  Silurian 
and  Devonian  rocks. 

*  Horner,  Trans,  of  Geol.  Soc.  2d  ser.  vcL  v. 


CH.  XXXL]  AGE   OF  THE  BROWN  COAL.  539 

through  them.  They  contain  numerous  impressions  of  leaves  and  stems 
of  trees,  and  are  extensively  worked  for  fuel,  whence  the  name  of  the 
formation. 

In  several  places,  layers  of  trachytic  tuff  are  interstratified,  and  in  these 
tuffs  are  leaves  of  plants  identical  with  those  found  in  the  brown-coal, 
showing  that,  during  the  period  of  the  accumulation  of  the  latter,  some 
volcanic  products  were  ejected. 

Mr.  Von  Decken,  in  his  work  on  the  Siebengebirge,*  has  given  a 
copious  list  of  the  animal  and  vegetable  remains  of  the  freshwater  strata 
associated  with  the  brown-coal.  Plants  of  the  genera  Flabellaria. 
Ceanothus,  and  Daphnogene,  including  D.  cinnamomifolia  (fig.  169, 
p.  191),  occur  in  these  beds,  with  nearly  150  other  plants,  if  we  include 
all  which  have  been  named  from  the  somewhat  uncertain  data  furnished 
by  leaves.  They  are  referred  for  the  most  part  to  living  genera,  but  to 
extinct  species.  Among  the  animal  remains,  both  vertebrate  and  inver- 
tebrate, many  are  peculiar,  while  some  few,  such  as  Littorinella  acuta, 
Desh.,  help  to  approximate  these  strata  with  some  of  the  upper  fresh- 
water portions  of  the  Mayence  basin.  The  marine  base  of  the  Mayence 
series  consists  of  sandy  strata  closely  allied,  in  geological  date,  as  we 
have  already  seen,  p.  1 90,  to  the  Limburg  group,  called  Upper  Eocene 
in  this  work.  But  in  regard  to  the  Rhenish  freshwater  deposits  near 
Bonn,  so  large  a  proportion  of  the  plants,  insects,  fish,  batrachians,  and 
other  fossils,  are  such  as  have  been  met  with  nowhere  else,  that  we 
cannot  as  yet  assign  to  them  a  very  definite  place  in  the  chronological 
series.  They  were  undoubtedly  formed  during  that  long  interval  of  time 
which  separated  the  Nummulitic  from  the  Falunian  tertiary  formations, 
so  that  they  are  newer  than  the  Middle  Eocene,  and  older  than  the 
Miocene  strata  of  our  Table  given  at  p.  104.  The  classification  of  the 
deposits  belonging  to  this  interval  must  still  be  regarded  as  debatable 
ground,  very  different  opinions  being  entertained  on  the  subject  by 
geologists  of  high  authority.  Should  a  passage  be  eventually  made 
out  from  the  tertiaries  of  the  north  of  Germany,  on  which  the  labors 
of  M.  Beyrich  have  thrown  so  much  light,  to  the  faluns  of  the  Loire, 
by  the  discovery  of  beds  intermediate  in  age  and  paleoutological  char- 
acters, the  best  line  of  demarcation  that  we  can  adopt  is  that  pro- 
posed by  M.  Hebert,  according  to  which  all  the  Limburg  beds,  the 
Gres  de  Fontainebleau,  the  lower  part  of  the  Mayence  basin,  and 
the  Hempstead  beds  of  the  Isle  of  Wight  (see  p.  192),  are  classed  as 
Lower  Miocene,  while  the  Faluns  rank  as  Upper  Miocene.  Between 
these  formations  there  is  still  so  vast  an  hiatus,  that  I  have  thought  it 
inexpedient,  for  reasons  before  explained,  to  unite  them  under  a  common 
name.f 

*  Geognost.  Beschreib.  des  Siebengebirges  am  Rhein.  Bonn.  1852. 

•j-  "While  this  sheet  was  passing  through  the  press,  a  valuable  paper  on  the 
Brown-Coal  and  other  deposits  of  the  Mayence  Basin,  by  "William  J.  Hamilton, 
Esq.,  P.  G.  S.,  has  been  published  (Geol.  Quart.  Journ.,  vol.  x.  p.  254),  in  which 
the  question  of  classification  above  alluded  to  is  discussed.  Whatever  termi- 


540  TEKTIAKY  VOLCANIC  ROCKS.  [On.  XXXI. 

The  fishes  of  the  brown-coal  near  Bonn  are  found  in  a  bituminous  shale, 
called  paper-coal,  from  being  divisible  into  extremely  thin  leaves.  The 
individuals  are  very  numerous ;  but  they  appear  to  belong  to  a  small 
number  of  species,  some  of  which  were  referred  by  Agassiz  to  the  genera 
Leuciscus,  Aspius,  and  Perca.  The  remains  of  frogs  also,  of  extinct 
species,  have  been  discovered  in  the  paper-coal ;  and  a  complete  series 
may  be  seen  in  the  museum  at  Bonn,  from  the  most  imperfect  state  of 
the  tadpole  to  that  of  the  full-grown  animal.  With  these  a  salamander, 
scarcely  distinguishable  from  the  recent  species,  has  been  found,  and  the 
remains  of  many  insects. 

A  vast  deposit  of  gravel,  chiefly  composed  of  pebbles  of  white  quartz, 
but  containing  also  a  few  fragments  of  other  rocks,  lies  over  the  brown- 
coal,  forming  sometimes  only  a  thin  covering,  at  others  attaining  a 
thickness  of  more  than  100  feet.  This  gravel  is  v«ry  distinct  in  char- 
acter from  that  now  forming  the  bed  of  the  Rhine.  It  is  called  "  Kiesel 
gerolle"  by  the  Germans,  often  reaches  great  elevations,  and  is  covered  in 
several  places  with  volcanic  ejections.  It  is  evident  that  the  country  has 
undergone  great  changes  in  its  physical  geography  since  this  gravel  was 
formed  5  for  its  position  has  scarcely  any  relation  to  the  existing  drainage, 
and  the  great  valley  of  the  Rhine  and  all  the  more  modern  volcanic 
rocks  of  the  same  .region  are  posterior  to  it  in  date. 

Some  of  the  newest  beds  of  volcanic  sand,  pumice,  and  scoriae,  are 
interstratified  near  Andernach  and  elsewhere  with  the  loam  called  loess, 
which  was  before  described  as  being  full  of  land  and  freshwater  shells  of 
recent  species,  and  referable  to  the  Post-Pliocene  period.  I  have  before 
hinted  (see  p.  123),  that  this  intercalation  of  volcanic  matter  between 
beds  of  loess  may  possibly  be  explained  without  supposing  the  last  erup- 
tions of  the  Lower  Eifel  to  have  taken  place  so  recently  as  the  era  of  the 
deposition  of  the  loess. 

The  igneous  rocks  of  the  Westerwald,  and  of  the  mountains  called 
the  Siebengebirge,  consist  partly  of  basaltic  and  partly  of  trachytic  lavas, 
the  latter  being  in  general  the  more  ancient  of  the  two.  There  are 
many  varieties  of  trachyte,  some  of  which  are  highly  crystalline,  resem- 
bling a  coarse-grained  granite,  with  large  separate  crystals  of  felspar. 
Trachytic  tuff  is  also  very  abundant.  .These  formations,  some  of  which 
were  certainly  contemporaneous  with  the  origin  of  the  brown-coal,  were 
the  first  of  a  long  series  of  eruptions,  the  more  recent  of  which  hap- 
pened when  the  country  had  acquired  nearly  all  its  present  geographical 
features. 

Newer  volcanos  of  the  Eifel. — Lake  craters. — As  I  recognized  in  the 
more  modern  volcanos  of  the  Eifel  characters  distinct  from  any  pre- 
viously observed  by  me  in  those  of  France,  Italy,  or  Spain,  I  shall  briefly 
describe  them.  The  fundamental  rocks  of  the  district  are  gray  and  red 

nology  be  adopted,  I  would  strongly  urge  the  necessity  of  referring  the  Hemp- 
stead  beds  of  the  Isle  of  Wight  and  the  Limburg  strata  to  one  and  the  same 
period,  whether  it  be  named  Lower  Miocene  or  Upper  Eocene. 


CH,  XXXI.] 


TERTIARY   VOLCANIC  ROCKS. 


sandstones  and  shales,  with  some  associated  limestones,  replete  with  fossils 
of  the  Devonian  or  Old  Red  Sandstone  group.  The  volcanos  broke  out 
in  the  midst  of  these  inclined  strata,  and  when  the  present  systems  of 
hills  and  valleys  had  already  been  formed.  The  eruptions  occurred 
sometimes  at  the  bottom  of  deep  valleys,  sometimes  on  the  summit  of 
hills,  and  frequently  on  intervening  platforms.  In  travelling  through 
this  district  we  often  fall  upon  them  most  unexpectedly,  and  find  ourselves 
on  the  very  edge  of  a  crater  before  we  had  been  led  to  suspect  that  we 
were  approaching  the  site  of  any  igneous  outburst.  Thus,  for  example, 
on  arriving  at  the  village  of  Gemund,  immediately  south  of  Daun,  we 
leave  the  stream,  which  flows  at  the  bottom  of  a  deep  valley  in  which 
strata  of  sandstone  and  shale  crop  out.  We  then  climb  a  steep  hill,  on 
the  surface  of  which  we  see  the  edges  of  the  same  strata  dipping  inwards 
towards  the  mountain.  When  we  have  ascended  to  a  considerable  height, 
we  see  fragments  of  scoriae  sparingly  scattered  over  the  surface  ;  until,  at 
length,  on  reaching  the  summit,  we  find  ourselves  suddenly  on  the  ecge 
of  a  tarn,  or  deep  circular  lake-basin  (see  fig.  673). 

rig.  eia 


The  Gemunder  Maar. 


Fig.  674. 


a.  Village  of  Gemund 
Z>.  Gemunder  Maar. 


c.  Weinfeldcr  Maar. 

d.  Schalkenmchren  Maar. 


This,  which  is  called  the  Gemunder  Maar,  is  one  of  three  lakes  which 
are  in  immediate  contact,  the  same  ridge  forming  the  barrier  of  two 
neighboring  cavities.  On  viewing  the  first  of  these  (fig.  673),  we  recog- 
nize the  ordinary  form  of  a  crater,  for  which  we  have  been  prepared  by 
the  occurrence  of  scoriae  scattered  over  the  surface  of  the  soil.  But  on 
examining  the  walls  of  the  crater,  we  find  precipices  of  sandstone  and 


542  LAKE  CKATERS  OF  THE  EIFEL.  [Ca  XXXI. 

shale  which  exhibit  no  signs  of  the  action  of  heat ;  and  we  look  in  vain 
for  those  beds  of  lava  and  scorise,  dipping  in  opposite  directions  on 
every  side,  which  we  have  been  accustomed  to  consider  as  characteristic 
of  volcanic  vents.  As  we  proceed,  however,  to  the  opposite  side  of  the  lake, 
and  afterwards  visit  the  craters  c  and  d  (fig.  674),  we  find  a  considerable 
quantity  of  scoriae  and  some  lava,  and  see  the  whole  surface  of  the  soil 
sparkling  with  volcanic  sand,  and  strewed  with  ejected  fragments  of  half- 
fused  shale,  which  preserves  its  laminated  texture  in  the  interior,  while  it 
has  a  vitrified  or  scoriform  coating. 

A  few  miles  to  the  south  of  the  lakes  above  mentioned,  occurs  the 
Pulvermaar  of  Gillenfeld,  an  oval  lake  of  very  regular  form,  and  sur- 
rounded by  an  unbroken  ridge  of  fragmentary  materials,  consisting  of 
ejected  shale  and  sandstone,  and  preserving  a  uniform  height  of  about 
150  feet  above  the  water.  The  side  slope  in  the  interior  is  at  an  angle 
of  about  forty-five  degrees  ;  on  the  exterior,  of  thirty-five  degrees. 
Volcanic  substances  are  intermixed  very  sparingly  with  the  ejections, 
which  in  this  place  entirely  conceal  from  view  the  stratified  rocks  of  the 
country.* 

The  Meerfelder  Maar  is  a  cavity  of  far  greater  size  and  depth,  hol- 
lowed out  of  similar  strata ;  the  sides  presenting  some  abrupt  sections 
of  inclined  secondary  rocks,  which  in  other  places  are  buried  under  vast 
heaps  of  pulverized  shale.  I  could  discover  no  scoriaB  amongst  the 
ejected  materials,  but  balls  of  olivine  and  other  volcanic  substances  are 
mentioned  as  having  been  found.f  This  cavity,  which  we  must  suppose 
to  have  discharged  an  immense  volume  of  gas,  is  nearly  a  mile  in 
diameter,  and  is  said  to  be  more  than  one  hundred  fathoms  deep.  In 
the  neighborhood  is  a  mountain  called  the  Mosenberg,  which  consists 
of  red  sandstone  and  shale  in  its  lower  parts,  but  supports  on  its 
summit  a  triple  volcanic  cone,  while  a  distinct  current  of  lava  is  seen 
descending  the  flanks  of  the  mountain.  The  edge  of  the  crater  of  the 
largest  cone  reminded  me  of  the  form  and  characters  of  that  of  Vesuvius  ; 
but  I  was  much  struck  with  the  precipitous  and  almost  overhanging 
wall  or  parapet  which  the  scoriae  presented  towards  the  exterior,  as  at  a  b 
(fig.  6*75),  which  I  can  only  explain  by  supposing  that  fragments  of  red-hot 


Stratified  rocks.  «.  Yolcanic. 

Outline  of  the  Mosenberg,  Upper  Eifel. 

*  Scrope,  Edin.  Journ.  of  Science,  June,  1826,  p.  145. 
\  Hibbert,  Extinct  Volcanos  of  the  Rhine,  p.  24. 


CH.  XXXI.]  MIOCENE  VOLCANIC  ROCKS.  543 

lava,  as  they  fell  round  the  vent,  were  cemented  together  into  one  com- 
pact mass,  in  consequence  of  continuing  to  be  in  a  half-melted  state. 

If  we  pass  from  the  upper  to  the  lower  Eifel,  from  A  to  B  (see  map,  p. 
538),  we  find  the  celebrated  lake-crater  of  Laach,  which  has  a  greater  re- 
semblance than  any  of  those  before  mentioned  to  the  Lago  di  Bolsena, 
and  others  in  Italy — being  surrounded  by  a  ridge  of  gently  sloping  hills, 
composed  of  loose  tuffs,  scoriae,  and  blocks  of  a  variety  of  lavas. 

One  of  the  most  interesting  volcanos  on  the  left  bank  of  the  Rhine,  near 
Bonn,  is  called  the  Roderberg.  It  forms  a  circular  crater  nearly  a  quarter 
of  a  mile  in  diameter,  and  100  feet  deep,  now  covered  with  fields  of  corn. 
The  highly  inclined  strata  of  ancient  sandstone  and  shale  rise  even  to 
the  rim  of  one  side  of  the  crater ;  but  they  are  overspread  by  quartzose 
gravel,  and  this  again  is  covered  by  volcanic  scoriae  and  tufaceous  sand. 
The  opposite  wall  of  the  crater  is  composed  of  cinders  and  scorified 
rock,  like  that  at  the  summit  of  Vesuvius.  It  is  quite  evident  that  the 
eruption  in  this  case  burst  through  the  sandstone  and  alluvium  which 
immediately  overlies  it;  and  I  observed  some  of  the  quartz  pebbles 
mixed  with  scoriae  on  the  flanks  of  the  mountain,  as  if  they  had  been 
cast  up  into  the  air,  and  had  fallen  again  with  the  volcanic  ashes.  I 
have  already  observed,  that  a  large  part  of  this  crater  has  been  filled  up 
with  loess  (p.  123). 

The  most  striking  peculiarity  of  a  great  many  of  the  craters  above 
described,  is  the  absence  of  any  signs  of  alteration  or  torrefaction  in 
their  walls,  when  these  are  composed  of  regular  strata  of  ancient  sand- 
stone and  shale.  It  is  evident  that  the  summits  of  hills  formed  of  the 
above-mentioned  stratified  rocks  have,  in  some  cases,  been  carried  away 
by  gaseous  explosions,  while  at  the  same  time  no  lava,  and  often  a  very 
small  quantity  only  of  scoria,  has  escaped  from  the  newly-formed  cavity. 
There  is,  indeed,  no  feature  in  the  Eifel  volcanos  more  worthy  of  note, 
than  the  proofs  they  afford  of  very  copious  aeriform  discharges,  unac- 
companied by  the  pouring  ont  of  melted  matter,  except,  here  and  there, 
in  very  insignificant  volume.  I  know  of  no  other  extinct  volcanos 
where  gaseous  explosions  of  such  magnitude  have  been  attended  by  the 
emission  of  so  small  a  quantity  of  lava.  Yet  I  looked  in  vain  in  the 
Eifel  for  any  appearances  which  could  lend  support  to  the  hypothesis, 
that  the  sudden  rushing  out  of  such  enormous  volumes  of  gas  had  ever 
'if ted  up  the  stratified  rocks  immediately  around  the  vent,  so  as  to  form 
conical  masses,  having  their  strata  dipping  outwards  on  all  sides  from  a 
central  axis,  as  is  assumed  in  the  theory  of  elevation  craters,  alluded  to 
in  Chap.  XXIX. 

Trass. — In  the  Lower  Eifel,  eruptions  of  trachytic  lava  preceded  the 
emission  of  currents  of  basalt,  and  immense  quantities  of  pumice  were 
thrown  out  wherever  trachyte  issued.  The  tufaceous  alluvium  called 
trass,  which  has  covered  large  areas  in  this  region  and  choked  up  some 
valleys  now  partially  re-excavated,  is  unstratified.  Its  base  consists 
almost  entirely  of  pumice,  in  which  are  included  fragments  of  basalt 
and  other  lavas,  pieces  of  burnt  shale,  slate,  and  sandstone,  and  nume- 


544  HUNGAKY.  [Cn.  XXXI. 

rous  trunks  and  branches  of  trees.  If  this  trass  was  formed  during  the 
period  of  volcanic  eruptions  it  may  perhaps  have  originated  in  the  man- 
ner of  the  moya  of  the  Andes. 

We  may  easily  conceive  that  a  similar  mass  might  now  be  produced, 
if  a  copious  evolution  of  gases  should  occur  in  one  of  the  lake  basins. 
The  water  might  remain  for  weeks  in  a  state  of  violent  ebullition,  until 
it  became  of  the  consistency  of  mud,  just  as  the  sea  continued  to  be 
charged  with  red  mud  round  Graham's  Island,  in  the  Mediterranean,  in 
the  year  1831.  If  a  breach  should  then  be  made  in  the  side  of  the 
cone,  the  flood  would  sweep  away  great  heaps  of  ejected  fragments  of 
shale  and  sandstone,  which  would  be  borne  down  into  the  adjoining 
valleys.  Forests  might  be  torn  up  by  such  a  flood,  and  thus  the  occur- 
rence of  the  numerous  trunks  of  trees  dispersed  irregularly  through  the 
trass,  can  be  explained. 

Hungary. — M.  Beudant,  in  his  elaborate  work  on  Hungary,  describes 
five  distinct  groups  of  volcanic  rocks,  which,  although  nowhere  of  great 
extent,  form  striking  features  in  the  physical  geography  of  that  country, 
rising  as  they  do  abruptly  from  extensive  plains  composed  of  tertiary 
strata.  They  may  have  constituted  islands  in  the  ancient  sea,  as  Santo- 
rin  and  Milo  now  do  in  the  Grecian  Archipelago ;  and  M.  Beudant  has 
remarked  that  the  mineral  products  of  the  last-mentioned  islands  resem- 
ble remarkably  those  of  the  Hungarian  extinct  volcanos,  where  many 
of  the  same  minerals,  as  opal,  chalcedony,  resinous  silex  (silex  resinite), 
pearlite,  obsidian,  and  pitchstone  abound. 

The  Hungarian  lavas  are  chiefly  felspatjiic,  consisting  of  different 
varieties  of  trachyte ;  many  are  cellular,  and  used  as  millstones ;  some 
so  porous  and  even  scoriform  as  to  resemble  those  which  have  issued  in 
the  open  air.  Pumice  occurs  in  great  quantity ;  and  there  are  conglom- 
erates, or  rather  breccias,  wherein  fragments  of  trachyte  are  bound 
together  by  pumiceous  tuff,  or  sometimes  by  silex. 

It  is  probable  that  these  rocks  were  permeated  by  the  waters  of  hot 
springs,  impregnated,  like  the*  Geysers,  with  silica ;  or  in  some  instances, 
perhaps,  by  aqueous  vapours,  which,  like  those  of  Lancerote,  may  have 
precipitated  hydrate  of  silica. 

By  the  influence  of  such  springs  or  vapours  the  trunks  and  branches 
of  trees  washed  down  during  floods,  and  b'uried  in  tuffs  on  the  flanks 
of  the  mountains,  are  supposed  to  have  become  siJicificd.  It  is  scarcely 
possible,  says  M.  Beudant,  to  dig  into  any  of  the  pumiceous  deposits  of 
these  mountains  without  meeting  with  opalized  wood,  and  sometimes 
entire  silicified  trunks  of  trees  of  great  size  and  weight. 

It  appears  from  the  species  of  shells  collected  principally  by  M.  Boue*, 
and  examined  by  M.  Deshayes,  that  the  fossil  remains  imbedded  in  the 
volcanic  tuffs,  and  in  strata  alternating  with  them  in  Hungary,  are  of 
the  Miocene  type,  and  not  identical,  as  was  formerly  supposed,  with  the 
fossils  of  the  Paris  basin. 


CH.  XXXH]  TERTIARY  VOLCANIC  ROCKS.  545 

CHAPTER  XXXE. 

ON   THE    DIFFERENT    AGES    OF   THE    VOLCANIC    ROCKS Continued. 

Volcanic  rocks  of  the  Pliocene,  Miocene,  and  Eocene  periods  continued — Au- 
vergne — Mont  Dor — Breccias  nnd  alluviums  of  Mont  Perrier,  with  bones  of 
quadrupeds — River  dammed  up  by  lava-current — Range  of  minor  cones  from 
Auvergne  to  the  Vivarais — Monts  Dome — Puy  de  C6me — Puy  de  Pariou — 
Cones  not  denuded  by  general  flood — Velay — Bones  of  quadrupeds  buried  in 
scorise — Cantal — Eocene  volcanic  rocks — Tuffs  near  Clermont — Hill  of  Ger- 
govia — Trap  of  Cretaceous  period — Oolitic  period — Xew  Red  Sandstone  pe- 
riod— Carboniferous  period — Old  Red  Sandstone  period — "Rock  and  Spindle" 
near  St.  Andrew's — Silurian  period — Cambrian  volcanic  rocks. 

Volcanic  Rocks  of  Auvergne. — THE  extinct  volcanos  of  Auvergne  and 
Cantal  in  Central  France  seem  to  have  commenced  their  eruptions  in  the 
Upper  Eocene  period,  but  to  have  been  most  active  during  the  Miocene 
and  Pliocene  eras.  I  have  already  alluded  to  the  grand  succession  of 
events,  of  which  there  is  evidence  in  Auvergne  since  the  last  retreat  of 
the  sea  (see  p.  196). 

The  earliest  monuments  of  the  tertiary  period  in  that  region  are 
lacustrine  deposits  of  great  thickness  (2,  fig.  676,  p.  547),  in  the  lowest 
conglomerates  of  which  are  rounded  pebbles  of  quartz,  mica-schist, 
granite,  and  other  non-volcanic  rocks,  without  the  slightest  intermixture 
of  igneous  products.  To  these  conglomerates  succeed  argillaceous  and 
calcareous  marls  and  limestones  (3,  fig.  607)  containing  upper  Eocene 
shells  and  bones  of  mammalia,  the  higher  beds  of  which  sometimes  al- 
ternate with  volcanic  tuff  of  contemporaneous  origin.  After  the  filling 
up  or  drainage  of  the  ancient  lakes,  huge  piles  of  trachytic  and  basaltic 
rocks,  with  volcanic  breccias,  accumulated  to  a  thickness  of  several  thou- 
sand feet,  and  were  superimposed  upon  granite,  or  the  contiguous  lacus- 
trine strata.  The  greater  portion  of  these  igneous  rocks  appear  to  have 
originated  during  the  Miocene  and  Pliocene  periods ;  and  extinct  quad- 
rupeds of  those  eras,  belonging  to  the  genera  Mastodon,  Rhinoceros, 
and  others,  were  buried  in  ashes  and  beds  of  alluvial  sand  and  gravel, 
which  owe  their  preservation  to  overspreading  sheets  of  lava. 

In  Auvergne  the  most  ancient  and  conspicuous  of  the  volcanic  masses 

is  Mont  Dor,  which  rests  immediately  on  the  granitic  rocks  standing 

apart  from  the  fresh-water  strata.*     This  great  mountain  rises  suddenly 

to  the  height  of  several  thousand  feet  above  the  surrounding  platform, 

and  retains  the  shape  of  a  flattened  and  somewhat  irregular  cone,  all  the 

sides  sloping  more  or  less  rapidly,  until  their  inclination  is  gradually 

lost  in  the  high  plain  around.    This  cone  is  composed  of  layers  of  scoria?, 

pumice  stones,  and  their  fine  detritus,  with  interposed  beds  of  trachyte 

*  See  the  map,  p.  195. 

35 


546  MONT  DOE,  AUVEKGNE.  [Ca  XXXII. 

and  basalt,  which  descend  often  in  uninterrupted  sheets,  until  they  reach 
and  spread  themselves  round  the  base  of  the  mountain.*  Conglome* 
rates  also,  composed  of  angular  and  rounded  fragments  of  igneous  rocks, 
are  observed  to  alternate  with  the  above ;  and  the  various  masses  are 
seen  to  dip  off  from  the  central  axis,  and  to  lie  parallel  to  the  sloping 
flanks  of  the  mountain. 

The  summit  of  Mont  Dor  terminates  in  seven  or  eight  rocky  peaks, 
where  no  regular  crater  can  now  be  traced,  but  where  we  may  easily 
imagine  one  to  have  existed,  which  may  have  been  shattered  by  earth- 
quakes, and  have  suffered  degradation  by  aqueous  agents.  Originally, 
perhaps,  like  the  highest  crater  of  Etna,  it  may  have  formed  an  insig- 
nificant feature  in  the  great  pile,  and  may  frequently  have  been  destroyed 
and  renovated. 

According  to  some  geologists,  this  mountain,  as  well  as  Vesuvius, 
Etna,  and  all  large  volcanos,  has  derived  its  dome-like  form  not  from 
the  preponderance  of  eruptions  from  one  or  more  central  points,  but 
from  the  upheaval  of  horizontal  beds  of  lava  and  scoriae.  I  have 
explained  my  reasons  for  objecting  to  this  view  in  Chapter  XXIX., 
when  speaking  of  Palma,  and  in  the  Principles  of  Geology .f  The 
average  inclination  of  the  dome-shaped  mass  of  Mont  Dor  is  8°  6', 
whereas  in  Mounts  Loa  and  Kea,  before  mentioned,  in  the  Sandwich 
Islands  (see  fig.  640,  p.  490),  the  flanks  of  which  have  been  raised  by 
recent  lavas,  we  find  from  Mr.  Dana's  description  that  the  one  has  a 
slope  of  6°  30',  the  other  of  7°  46'.  We  may,  therefore,  reasonably 
question  whether  there  is  any  absolute  necessity  for  supposing  that  the 
basaltic  currents  of  the  ancient  French  volcano  were  at  first  more  hori- 
zontal than  they  are  now.  Nevertheless  it  is  highly  probable  that 
during  the  long  series  of  eruptions  required  to  give  rise  to  so  vast  a  pile 
of  volcanic  matter,  which  is  thickest  at  the  summit  or  centre  of  the 
dome,  some  dislocation  and  upheaval  took  place ;  and  during  the  disten- 
sion of  the  mass,  beds  of  lava  and  scoriae  may,  in  some  places,  have 
acquired  a  greater,  in  others  a  less  inclination,  than  that  which  at  first 
belonged  to  them. 

Respecting  the  age  of  the  great  mass  of  Mont  Dor,  we  cannot  come 
at  present  to  any  positive  decision,  because  no  organic  remains  have  yet 
been  found  in  the  tuffs,  except  impressions  of  the  leaves  of  trees  of 
species  not  yet  determined.  We  may  certainly  conclude,  that  the  ear- 
liest eruptions  were  posterior  in  origin  to  those  grits,  and  conglomerates 
of  the  fresh-water  formation  of  the  Limagne,  which  contain  no  pebbles 
of  volcanic  rocks ;  while,  on  the  other  hand,  some  eruptions  took  place 
before  the  great  lakes  were  drained;  and  others  occurred  after  the 
desiccation  of  those  lakes,  and  when  deep  valleys  had  aleady  been  exca- 
vated through  fresh-water  strata. 

In  the  annexed  section,  I  have  endeavored   to  explain  the  geological 
structure  of  a  portion  of  Auvergne,  which  I  re-examined  in  1843.J     It 
*  Scrope's  Central  France,  p.  98. 

f  See  chaps,  xxiv.  xxv.  and  xxvi.  7th,  8th,  and  9th  editions, 
j  See  Quarterly  Geol.  Journ.  voL  ii.  p.  77. 


CH.  XXXII]  TERTIARY  VOLCANIC  ROCKS.  54Y 


Fig.  6T6. 

Mont  Perrier. 

*•                         Sc          s* 

nfljf  of  the       Toor  . 

5 

/"nTiTgrrrn    '.—^aimM^fc-    >     * 

Allier.              Boula.1 

3\ 

c°BzeR-          vi^^MB^ 

t        "-*•      .,/? 

w& 

^       «^^^x^^^:^^->^^«^^ 

Section  from  the  valley  of  the  Couze  at  Nechers,  through  Mont  Perrier  and  Issoire  to  the  Vallej 
of  the  Allier,  and  the  Tour  de  Boulade,  Auvergne. 

10.  Lara-current  of  Tartaret  near  its  termina-  5.    Lower  bone-bed  of  Perrier,  ochreous  sand 
tion  at  Nechers.  and  gravel. 

9.  Bone-bed,  red  sandy  clay  under  the  lava  of  4  a.  Basaltic  dyke. 

Tartaret.  4.  Basaltic  platform. 

8.  Bone-bed  of  the  Tour  de  Boulade.  3.  Upper   fresh-water   beds,  limestone,  marl, 

7.  Alluvium  newer  than  No.  6.  gypsum,  Ac. 

6.  Alluvium  with  bones  of  hippopotamus.  2.  Lower  fresh-water  formation,  red  clay,  green 

5  c.  Trachytic  breccia  resembling  5  a.  sand,  Ac. 

5  b.  Upper  bone-bed  of  Perrier,  gravel,  Ac.  1.  Granite. 

5  a.  Pumiceous  breccia  and  conglomerate,  angu- 
lar masses  of  trachyte,  quartz,  pebbles,  Ac. 

may  convey  some  idea  to  the  reader  of  the  long  and  .  om  plicated  series 
of  events  which  have  occurred  in  that  country,  since  the  first  lacustrine 
strata  (No.  2)  were  deposited  on  the  granite  (No.  1).  The  changes  of 
which  we  have  evidence  are  the  more  striking,  because  they  imply  great 
denudation,  without  there  being  any  proofs  of  the  intervention  of  the 
sea  during  the  whole  period.  It  will  be  seen  that  the  upper  fresh-water 
beds  (No.  3j,  once  formed  in  a  lake,  must  have  suffered  great  destruc- 
tion before  the  excavation  of  the  valleys  of  the  Couze  and  Allier  had 
begun.  In  these  fresh-water  beds,  Upper  Eocene  fossils,  as  described 
in  Chap.  XV.,  have  been  found.  The  basaltic  dike  4'  is  one  of  many 
examples  of  the  intrusion  of  volcanic  matter  through  the  Eocene  fresh- 
water beds,  and  may  have  been  of  Upper  Eocene  or  Miocene  date,  giv- 
ing rise,  when  it  reached  the  surface  and  overflowed,  to  such  platforms 
of  basalt,  as  often  cap  the  tertiary  hills  in  Auvergne,  and  one  of  which 
(4)  is  seen  on  Mont  Perrier. 

It  not  unfrequently  happens  that  beds  of  gravel  containing  bones  of 
extinct  mammalia  are  detected  under  these  very  ancient  sheets  of  basalt, 
as  between  No.  4  and  the  fresh-water  strata,  No.  3,  at  A,  from  which  it 
is  clear  that  the  surface  of  No.  3  formed  at  that  period  the  lowest  level  at 
which  the  waters  then  draining  the  country  flowed.  Next  in  age  to  this 
basaltic  platform  comes  a  patch  of  ochreous  sand  and  gravel  (No.  5), 
containing  many  bones  of  quadrupeds.  Upon  this  rests  a  pumiceous 
breccia  or  conglomerate,  with  angular  masses  of  trachyte,  and  some 
quartz  pebbles.  This  deposit  is  followed  by  5  b,  which  is  similar  to  5, 
and  5  c  similar  to  the  trachytic  breccia  5  a.  These  two  breccias  are 
supposed,  from  their  similarity  to  others  found  on  Mount  Dor,  to  have 
descended  from  the  flanks  of  that  mountain  during  eruptions ;  and  the 
interstratified  alluvial  deposits  contain  the  remains  of  mastodon,  rhino- 
ceros, tapir,  deer,  beaver,  and  quadrupeds  of  other  genera  referable  to 
about  forty  species,  all  of  which  are  extinct.  I  formerly  supposed  them 
to  belong  to  the  same  era  as  the  Miocene  faluns  of  Touraine;  but, 


548  VOLCANOS  OF  AUYEKGNE.  [Ca  XXXII 

whether  they  may  not  ratheft  be  ascribed  to  the  older  Pliocene  epoch  is 
a  question  which  farther  inquiries  and  comparisons  must  determine. 

Whatever  be  their  date  in  the  tertiaiy  series,  they  are  quadrupeds 
which  inhabited  the  country  when  the  formations  5  and  5  c  originated. 
Probably  they  were  drowned  during  floods,  such  as  rush  down  the  flanks 
of  volcanos  during  eruptions,  when  great  bodies  of  steam  are  emitted 
from  the  crater,  or  when,  as  we  have  seen,  both  on  Etna  and  in  Iceland 
in  modern  times,  large  masses  of  snow  are  suddenly  melted  by  lava,  causing 
a  deluge  of  water  to  bear  down  fragments  of  igneous  rocks  mixed  with 
mud,  to  the  valleys  and  plains  below. 

It  will  be  seen  that  the  valley  of  the  Issoire,  down  which  these  an- 
cient inundations  swept,  was  first  excavated  at  the  expense  of  the  for- 
mations 2,  3,  and  4,  and  then  filled  up  by  the  masses  5  and  5  c,  after 
which  it  was  re-excavated  before  the  more  modern  alluviums  (Nos.  6  and 
7)  were  formed.  In  these  again  other  fossil  mammalia  of  distinct  species 
have  been  detected  by  M.  Bravard,  the  bones  of  an  hippopotamus  having 
been  found  among  the  rest. 

At  length,  when  the  valley  of  the  Allier  was  eroded  at  Issoire  down 
to  its  lowest  level,  a  talus  of  angular  fragments  of  basalt  and  freshwater 
limestone  (No.  8)  was  formed,  called  the  bone-bed  of  the  Tour  de  Bou- 
lade,  from  which  a  great  many  other  mammalia  have  been  collected  by 
MM.  Bravard  and  Pomel.  In  this  assemblage  the  Eleplias  primigenius 
Rhinoceros  tichorinus,  Deer  (including  rein-deer),  Eqims,  Bos,  Antelope, 
FeliSj  and  Canis,  were  included.  Even  this  deposit  seems  hardly  to  be 
the  newest  in  the  neighbourhood,  for  if  we  cross  from  the  town  of  Issoire 
(see  fig.  6*76)  over  Mont  Perrier  to  the  adjoining  valley  of  the  Couze, 
we  find  another  bone-bed  (No.  9),  overlaid  by  a  current  of  lava  (No.  10). 

The  history  of  this  lava-current,  which  terminates  a  few  hundred 
yards  below  the  point  No.  10,  in  the  suburbs  of  the  village  of  Nechers, 
is  interesting.  It  forms  a  long  narrow  stripe  more  than  13  miles  in 
length,  at  the  bottom  of  the  valley  of  the  Couze,  which  flows  out  of  a 
lake  at  the  foot  of  Mont  Dor.  This  lake  is  caused  by  a  barrier 
thrown  across  the  ancient  channel  of  the  Couze,  consisting  partly  of  the 
volcanic  cone  called  the  Puy  de  Tartaret,  formed  of  loose  scoriae,  from 
the  base  of  which  has  issued  the  lava-current  before  mentioned.  The 
materials  of  the  dam  which  blocked  up  the  river,  and  caused  the  Lac  de 
Chambon,  are  also,  in  part,  derived  from  a  land-slip  which  may  have 
happened  at  the  time  of  the  great  eruptipn  which  formed  the  cone. 

This  cone  of  Tartaret  affords  an  impressive  monument  of  the  very 
different  dates  at  which  the  igneous  eruptions  of  Auvergne  have  hap- 
pened ;  for  it  was  evidently  thrown  up  at  the  bottom  of  the  existing 
valley,  which  is  bounded  by  lofty  precipices  composed  of  sheets  of  an- 
cient columnar  trachyte  and  basalt,  which  once  flowed  at  very  high  levels 
from  Mont  Dor.* 

*  For  a  view  of  Puy  de  Tartaret  and  Mont  Dor,  see  Scrope's  Volcanos  of  Cen- 
tral France. 


CH.  XXXIL]  TEKTIARY  VOLCANIC  ROCES.  549 

When  we  follow  the  course  of  the  river  Couze,  from  its  source  m  the 
lake  of  Chambon,  to  the  termination  of  the  lava-current  at  Nechers,  a  dis- 
tance of  thirteen  miles,  we  find  that  the  torrent  has  in  most  places  cut  a 
deep  channel  through  the  lava,  the  lower  portion  of  which  is  columnar. 
In  some  narrow  gorges  the  water  has  even  had  power  to  remove  the 
entire  mass  of  basaltic  rock,  though  the  work  of  erosion  must  have  been 
very  slow,  as  the  basalt  is  tough  and  hard,  and  one  column  after  another 
must  have  been  undermined  and  reduced  to  pebbles,  and  then  to  sand. 
During  the  time  required  for  this  operation,  the  perishable  cone  of  Tar- 
taret,  composed  of  sand  and  ashes,  has  stood  uninjured,  proving  that  no 
great  flood  or  deluge  can  have  passed  over  this  region  in  the  interval 
between  the  eruption  of  Tartaret  and  our  own  times. 

If  we  now  return  to  the  section  (fig.  676),  we  may  observe  that  the 
lava-current  of  Tartaret,  which  has  diminished  greatly  in  height  and 
volume  near  its  termination,  presents  here  a  steep  and  perpendicular 
face  25  feet  in  height  towards  the  river.  Beneath  it  is  the  alluvium 
No.  9,  consisting  of  a  red  sandy  clay,  which  must  have  covered  the 
bottom  of  the  valley  when  the  current  of  melted  rock  flowed  down. 
The  bones  found  in  this  alluvium,  which  I  obtained  myself,  consisted 
of  a  species  of  field-mouse,  Arvicola,  and  the  molar  tooth  of  an  extinct 
horse,  Equmfossilis.  The  other  species,  obtained  from  the  same  bed, 
are  referable  to  the  genera  Sus,  Bos,  Ccrvusf  Felis,  Canis,  Maries,  Talpa, 
SoreXj  LepuSj  Sciurm,  Mus,  and  Logomys,  in  all  no  less  than  forty- 
three  species,  all  closely  allied  to  recent  animals,  yet  nearly  all  of  them, 
according  to  M.  Bravard,  showing  some  points  of  difference,  like  those 
which  Mr.  Owen  discovered  in  the  case  of  the  horse  above  alluded  to. 
The  bones,  also,  of  a  frog,  snake,  and  lizard,  and  of  several  birds,  were 
associated  with  the  fossils  before  enumerated,  and  several  recent  land 
shells,  such  as  Cyclostoma  elegans,  Helix  liortensis,  H.  nemoralis,  H.  la- 
pitida,  and  Clausilia  rugosa.  If  the  animals  were  drowned  by  floods, 
which  accompanied  the  eruptions  of  the  Puy  de  Tartaret,  they  would  give 
an  exceedingly  modern  geological  date  to  that  event,  which  must,  in  that 
case,  have  belonged  to  the  Newer-Pliocene,  or,  perhaps,  the  Post-Plio- 
cene period.  That  the  current,  which  has  issued  from  the  Puy  de  Tar- 
taret, may  nevertheless  be  very  ancient  in  reference  to  the  events  of 
human  history,  we  may  conclude,  not  only  from  the  divergence  of  the 
mammiferous  fauna  from  that  of  our  day,  but  from  the  fact  that  a  Roman 
bridge  of  such  form  and  construction  as  continued  in  use  down  to  the 
fifth  century,  but  which  may  be  older,  is  now  seen  at  a  place  about  a 
mile  and  a  half  from  St.  Nectaire.  This  ancient  bridge  spans  the  river 
Couze  with  two  arches,  each  about  14  feet  wide.  These  arches  spring 
from  the  lava  of  Tartaret,  on  both  banks,  showing  that  a  ravine  pre- 
cisely like  that  now  existing,  had  already  been  excavated  by  the  river 
through  that  lava  thirteen  or  fourteen  centuries  ago. 

In  Central  France  there  are  several  hundred  minor  cones,  like  that 
of  Tartaret,  a  great  number  of  which,  like  Monte  Nuovo,  near  Naples, 
may  have  been  principally  due  to  a  single  eruption.  Most  of  these  cones 


550  VOLCANOS  OF  AUVERGNE.  [On.  XXXII. 

range  in  a  linear  direction  from  Auvergne  to  the  Vivarais,  and  they  were 
faithfully  described  so  early  as  the  year  1802,  by  M.  de  Montlosier.  They 
have  given  rise  chiefly  to  currents  of  basaltic  lava.  Those  of  Auvergne 
called  the  Monts  Dome,  placed  on  a  granitic  platform,  form  an  irregular 
ridge  (see  fig.  621,  p.  462),  about  18  miles  in  length,  and  2  in  breadth. 
They  are  usually  truncated  at  the  summit,  where  the  crater  is  often  pre- 
served entire,  the  lava  having  issued  from  the  base  of  the  hill.  But  fre- 
quently the  crater  is  broken  down  on  one  side,  where  the  lava  has  flowed 
out,  The  hills  are  composed  of  loose  scoriae,  blocks  of  lava,  lapilli,  and 
pozzuolana,  with  fragments  of  trachyte  and  granite. 

Puy  de  Cdme. — The  Puy  de  Come  and  its  lava-current,  near  Clermont, 
may  be  mentioned  as  one  of  these  minor  volcanos.  This  conical  hill  rises 
from  the  granitic  platform,  at  an  angle  of  between  30°  and  40°,  to  the 
height  of  more  than  900  feet.  Its  summit  presents  two  distinct  craters, 
one  of  them  with  a  vertical  depth  of  250  feet.  A  stream  of  lava  takes 
its  rise  at  the  western  base  of  the  hill,  instead  of  issuing  from  either  crater, 
and  descends  the  granitic  slope  towards  the  present  site  of  the  town  of 
Pont  Gibaud.  Thence  it  pours  in  a  broad  sheet  down  a  steep  declivity 
into  the  valley  of  the  Sioule,  filling  the  ancient  river-channel  for  the  dis- 
tance of  more  than  a  mile.  The  Sioule,  thus  dispossessed  of  its  bed,  has 
worked  out  a  fresh  one  between  the  lava  and  the  granite  of  its  western 
bank ;  and  the  excavation  has  disclosed,  in  one  spot,  a  wall  of  columnar 
basalt  about  50  feet  high.* 

The  excavation  of  the  ravine  is  still  in  progress,  every  winter  some 
columns  of  basalt  being  undermined  and  carried  down  the  channel  of  the 
river,  and  in  the  course  of  a  few  miles  rolled  to  sand  and  pebbles.  Mean- 
while the  cone  of  Come  remains  unimpaired,  its  loose  materials  being 
protected  by  a  dense  vegetation,  and  the  hill  standing  on  a  ridge  not  com- 
manded by  any  higher  ground,  so  that  no  floods  of  rain-water  can  descend 
upon  it.  There  is  no  end  to  the  waste  which  the  hard  basalt  may  undergo 
in  future,  if  the  physical  geography  of  the  country  continue  unchanged, 
no  limit  to  the  number  of  years  during  which  the  heap  of  incoherent  and 
transportable  materials  called  the  Puy  de  Come  may  remain  in  a  station- 
ary condition.  In  this  place,  therefore,  we  behold  in  the  results  of  aque- 
ous and  atmospheric  agency  in  past  times,  a  counterpart  of  what  we  must 
expect  to  recur  in  future  ages. 

Lava  of  Chaluzet. — At  another  point,  farther  down  the  course  of  the 
Sioule,  we  find  a  second  illustration  of  the  same  phenomenon  in  the  Puy 
Eouge,  a  conical  hill  to  the  north  of  the  village  of  Pranal.  The  cone  is 
composed  entirely  of  red  and  black  scoriae,  tuff,  and  volcanic  bombs.  On 
its  western  side,  towards  the  village  of  Chaluzet,  there  is  a  worn-down 
crater,  whence  a  powerful  stream  of  lava  has  issued,  and  flowed  into  the 
valley  of  the  Sioule.  The  river  has  since  excavated  a  ravine  through  the 
lava  and  subjacent  gneiss,  to  the  depth  in  some  places  of  400  feet. 

On  the  upper  part  of  the  precipice  forming  the  left  side  of  this  ravine, 

*  Scrope's  Central  France,  p.  60,  and  plate. 


CH.  XXXIL] 


TERTIARY  VOLCANIC   ROCKS. 


551 


we  see  a  great  mass  of  black  and  red  scoriaceous  lava  becoming  more 
and  more  columnar  towards  its  base.    (See  fig.  677).    Below  this  is  a  bed 


Fig.  677. 


a.  Scoriaceons  lava. 
6.  Columnar  basalt 
c.  Gravel 

D.  Ancient  mining  gallery. 

E.  Pathway. 
/  Gneiss. 


Lava-current  of  Chaluzet,  Auvergne,  near  its  termination.* 

of  sand  and  gravel  3  feet  thick,  evidently  an  ancient  river-bed,  now  at  an 
elevation  of  25  feet  above  the  channel  of  the  Sioule.  This  gravel,  from 
which  water  gushes  out,  rests  upon  gneiss,/,  which  has  been  eroded  to 
the  depth  of  25  feet  at  the  point  where  the  annexed  view  is  taken.  At 
D,  close  to  the  village  of  Les  Combres,  the  entrance  of  a  gallery  is  seen, 
in  which  lead  has  been  worked  in  the  gneiss.  This  mine  shows  that  the 
pebble-bed  is  continuous,  in  a  horizontal  direction,  between  the  gneiss  and 
the  volcanic  mass.  Here  again  it  is  quite  evident,  that,  while  the  basalt 
was  gradually  undermined  and  carried  away  by  the  force  of  running 
water,  the  cone  whence  the  lava  issued  escaped  destruction,  because  it 
stood  upon  a  platform  of  gneiss  several  hundred  feet  above  the  level  of 
the  valley  in  which  the  force  of  running  water  was  exerted. 

Puy  de  Pariou. — The  brim  of  the  crater  of  the  Puy  de  Pariou,  near 
Clermont,  is  so  sharp,  and  has  been  so  little  blunted  by  time,  that  it 
scarcely  affords  room  to  stand  upon.  This  and  other  cones  in  an  equally 
remarkable  state  of  integrity  have  stood,  I  conceive,  uninjured,  not  in 
spite  of  their  loose  porous  nature,  as  might  at  first  be  naturally  supposed, 
but  in  consequence  of  it.  JSTo  rills  can  collect  where  all  the  rain  is  in- 
stantly absorbed  by  the  sand  and  scoria?,  as  is  remarkably  the  case  on 
Etna  ;  and  nothing  but  a  waterspout  breaking  directly  upon  the  Puy  de 
Pariou  could  carry  away  a  portion  of  the  hill,  so  long  as  it  is  not  rent  or 
engulfed  by  earthquakes. 

*  Lyell  and  Murchison,  Ed.  New  PhiL  Journ.  1829. 


552  TERTIAEY  VOLCANIC   ROCKS.  [Cn.  XXXII. 

Hence  it  is  conceivable  that  even  those  cones  which  have  the  freshest 
aspect,  and  most  perfect  shape,  may  lay  claim  to  very  high  antiquity. 
Dr.  Daubeny  has  justly  observed,  that  had  any  of  these  volcanos  been 
in  a  state  of  activity  in  the  age  of  Julius  Caesar,  that  general,  who  en- 
camped upon  the  plains  of  Auvergne,  and  laid  siege  to  its  principal  city 
(Gergovia,  near  Ciermont),  could  hardly  have  failed  to  notice  them. 
Had  there  been  any  record  of  their  eruptions  in  the  time  of  Pliny  or  Si- 
donius  Apollinaris,  the  one  would  scarcely  have  omitted  to  make  mention 
of  it  in  his  Natural  History,  nor  the  other  to  introduce  some  allusion  to  it 
among  the  descriptions  of  this  his  native  province.  This  poet's  residence 
was  on  the  borders  of  the  Lake  Aidat,  which  owed  its  very  existence  to 
the  damming  up  of  a  river  by  one  of  the  most  modern  lava-currents.* 

Vclay.  —  The  observations  of  M.  Bertrand  de  Doue  have  not  yet  es- 
tablished that  any  of  the  most  ancient  volcanos  of  Velay  were  in  action 
during  the  Eocene  period.  There  are  beds  of  gravel  in  Velay,  as  in 
Auvergne,  covered  by  lava  at  different  heights  above  the  channel  of  the 
existing  rivers.  In  the  highest  and  most  ancient  of  these  alluviums  the 
pebbles  are  exclusively  of  granitic  rocks ;  but  in  the  newer,  which  are 
found  at  lower  levels,  and  which  originated  when  the  valleys  had  been 
cut  to  a  greater  depth,  an  intermixture  of  volcanic  rocks  has  been  ob- 
served. 

At  St.  Privat  d'Allier  a  bed  of  volcanic  scoriae  and  tuff  was  discovered 
by  Dr.  Hibbert,  inclosed  between  two  sheets  of  basaltic  lava ;  and  in 
this  tuff  were  found  the  bones  of  several  quadrupeds,  some  of  them 
adhering  to  masses  of  slaggy  lava.  Among  other  animals  were  Rhino- 
ceros leptorliinus,  Hyaena  speldea,  and  a  species  allied  to  the  spotted 
hyaena  of  the  Cape,  together  with  four  undetermined  species  of  deer. 
The  manner  of  the  occurrence  of  these  bones  reminds  us  of  the  pub- 
lished accounts  of  an  eruption  of  Coseguina,  1835,  in  Central  America 
(see  p.  521),  during  which  hot  cinders  and  scoriae  fell  and  scorched  to 
death  great  numbers  of  wild  and  domestic  animals  and  birds. 

Plomb  du  Cantal. — In  regard  to  the  age  of  the  igneous  rocks  of  the  Can- 
tal,  we  can  at  present  merely  affirm,  that  they  overlie  the  (Upper  ?)  Eocene 
lacustrine  strata  of  that  country  (see  Map,  p.  195).  They  form  a  great 
dome-shaped  mass,  having  an  average  slope  of  only  4°,  which  has  evi- 
dently been  accumulated,  like  the  cone  of  Etna,  during  a  long  series  of 
eruptions.  It  is  composed  of  trachytic,  phonolitic,  and  basaltic  lavas, 
tuffs,  and  conglomerates,  or  breccias,  forming  a  mountain  several  thou- 
sand feet  in  height.  Dikes  also  of  phonolite,  trachyte,  and  basalt  are 
numerous,  especially  in  the  neighbourhood  of  the  large  cavity,  probably 
once  a  crater,  around  which  the  loftiest  summits  of  the  Cantal  are 
ranged  circularly,  few  of  them,  except  the  Plomb  du  Cantal,  rising  far 
above  the  border  or  ridge  of  this  supposed  crater.  A  pyramidal  hill, 
called  the  Puy  Griou,  occupies  the  middle  of  the  cavity. f  It  is  clear 
that  the  volcano  of  the  Cantal  broke  out  precisely  on  the  site  of  the 
*  Daubeny  on  Volcanos,  p.  14. 
f  Mem.  de  la  Soc.  Geol.  de  France,  torn.  i.  p.  176. 


CH.  XXXIL]  EOCENE  VOLCANIC  ROCKS.  553 

lacustrine  deposit  before  described  (p.  204),  which  had  accumulated  in 
a  depression  of  a  tract  composed  of  micaceous  schist.  In  the  breccias, 
even  to  the  very  summit  of  the  mountain,  we  find  ejected  masses  of  the 
fresh-water  beds,  and  sometimes  fragments  of  flint,  containing  Eocene 
shells.  Valleys  radiate  in  all  directions  from  the  central  heights  of  the 
mountain,  increasing  in  size  as  they  recede  from  those  heights.  Those 
of  the  Cer  and  Jourdanne,  which  are  more  than  20  miles  in  length,  are 
of  great  depth,  and  lay  open  the  geological  structure  of  the  mountain. 
No  alternation  of  lavas  with  undisturbed  Eocene  strata  has  been  ob- 
served, nor  any  tuffs  containing  fresh-water  shells,  although  some  of 
these  tuffs  include  fossil  remains  of  terrestrial  plants,  said  to  imply  seve- 
ral distinct  restorations  of  the  vegetation  of  the  mountain  in  the  inter- 
vals between  great  eruptions.  On  the  northern  side  of  the  Plomb  du 
Cantal,  at  La  Vissiere,  near  Murat,  is  a  spot,  pointed  out  on  the  Map 
(p.  195),  where  fresh-water  limestone  and  marl  are  seen  covered  by  a 
thickness  of  about  800  feet  of  volcanic  rock.  Shifts  are  here  seen  in 
the  strata  of  limestone  and  marl.* 

In  treating  of  the  lacustrine  deposits  of  Central  France,  in  the  fifteenth 
chapter,  it  was  stated  that,  in  the  arenaceous  and  pebbly  group  of  the 
lacustrine  basins  of  Auvergne,  Cantal,  and  Velay,  no  volcanic  pebbles  had 
ever  been  detected,  although  massive  piles  of  igneous  rocks  are  now  found 
in  the  immediate  vicinity.  As  this  observation  has  been  confirmed  by 
minute  research,  we  are  warranted  in  inferring  that  the  volcanic  eruptions 
had  not  commenced  when  the  older  subdivisions  of  the  freshwater  groups 
originated. 

In  Cantal  and  Velay  no  decisive  proofs  have  yet  been  brought  to 
light  that  any  of  the  igneous  outbursts  happened  during  the  deposition 
of  the  fresh-water  strata ;  but  there  can  be  no  doubt  that  in  Auvergne 
some  volcanic  explosions  took  place  before  the  drainage  of  the  lakes, 
and  at  a  time  when  the  Upper  Eocene  species  of  animals  and  plants  still 
flourished.  Thus,  for  example,  at  Pont  du  Chateau,  near  Clermont,  a 
section  is  seen  in  a  precipice  on  the  right  bank  of  the  river  Allier,  in 
which  beds  of  volcanic  tuff  alternate  with  a  fresh-water  limestone,  which 
is  in  some  places  pure,  but  in  others  spotted  with  fragments  of  volcanic 
matter,  as  if  it  were  deposited  while  showers  of  sand  and  scoriae  were 
projected  from  a  neighboring  ventf 

Another  example  occurs  in  the  Puy  de  Marmont,  near  Veyres,  where 
a  fresh-water  marl  alternates  with  volcanic  tuff  containing  Eocene  shells. 
The  tuff  or  breccia  in  this  locality  is  precisely  such  as  is  known  to  result 
from  volcanic  ashes  falling  into  water,  and  subsiding  together  with 
ejected  fragments  of  marl  and  other  stratified  rocks.  These  tuffs  and 
marls  are  highly  inclined,  and  traversed  by  a  thick  vein  of  basalt,  which, 
as  it  rises  in  the  hill,  divides  into  two  branches. 

Gergovia. —  The  hill  of  Gergovia,  near  Clermont,  affords  a  third 
example.     I  agree  with  MM.  Dufrenoy  and  Jobert  that  there  is  no 
*  See  Lyell  and  Murchison,  Ann.  de  Sci.  Nat,,  Oct.  1829. 
f  See  Scrope's  Central  France,  p.  21. 


554: 


EOCENE  VOLCANIC  HOCKS. 


[On.  XXXII. 


alternation  here  of  a  contemporaneous  sheet  of  lava  with  freshwater 
strata  in  the  manner  supposed  by  some  other  observers  ;*  but  the  posi- 
tion and  contents  of  some  of  the  associated  tuffs,  prove  them  to  have 
been  derived  from  volcanic  eruptions  which  occurred  during  the  deposi- 
tion of  the  lacustrine  strata. 

The  bottom  of  the  hill  consists  of  slightly  inclined  beds  of  white  and 
greenish  marls,  more  than  300  feet  in  thickness,  intersected  by  a  dike 
of  basalt,  which  may  be  studied  in  the  ravine  above  the  village  of  Mer- 
dogne.  The  dike  here  cuts  through  the  marly  strata  at  a  considerable 
angle,  producing,  in  general,  great  alteration  and  confusion  in  them  for 
some  distance  from  the  point  of  contact.  Above  the  white  and  green 

Fig.  678. 


White 
and  green 
marls. 


Hill  of  Gergovia. 

marls,  a  series  of  beds  of  limestone  and  marl,  containing  fresh-water 
shells,  are  seen  to  alternate  with  volcanic  tuff.  In  the  lowest  part  of  this 
division,  beds  of  pure  marl  alternate  with  compact  fissile  tuff,  resembling 
some  of  the  subaqueous  tuffs  of  Italy  and  Sicily  called  peperinos.  Oc- 
casionally fragments  of  scoriae  are  visible  in  this  rock.  Still  higher  is 
seen  another  group  of  some  thickness,  consisting  exclusively  of  tuff, 
upon  which  lie  other  marly  strata  intermixed  with  volcanic  matter. 
Among  the  species  of  fossil  shells  which  I  found  in  these  strata  were 
Melania  inquinata,  a  Unio,  and  a  Melanop&t,  but  they  were  not  suffi- 
cient to  enable  me  to  determine  with  precision  the  age  of  the  formation. 
There  are  many  points  in  Auvergne  where  igneous  rocks  have  been 
forced  by  subsequent  injection  through  clays  and  marly  limestones,  in 
such  a  manner  that  the  whole  has  become  blended  in  one  confused  and 
brecciated  mass,  between  which  and  the  basalt  there  is  sometimes  no 
very  distinct  line  of  demarcation.  In  the  cavities  of  such  mixed  rocks 
we  often  find  chalcedony,  and  crystals  of  mesotype,  stilbite,  and  arrago- 
nite.  To  formations  of  this  class  may  belong  some  of  the  breccias 
immediately  adjoining  the  dike  in  the  hill  of  Gergovia;  but  it  cannot  be 
contended  that  the  volcanic  sand  and  scoriae  interstratified  with  the  marls 


*  See  Scrope's  Central  France,  p.  7. 


CH.  XXXII]  CRETACEOUS  VOLCANIC  ROCKS.  555 

and  limestones  in  the  upper  part  of  that  hill  were  introduced,  like  the 
dike,  subsequently,  by  intrusion  from  below.  They  must  have  been 
thrown  down  like  sediment  from  water,  and  can  only  have  resulted  from 
igneous  action,  which  was  going  on  contemporaneously  with  the  deposi- 
tion of  the  lacustrine  strata. 

The  reader  will  bear  in  mind  that  this  conclusion  agrees  well  with  the 
proofs,  adverted  to  in  the  fifteenth  chapter,  of  the  abundance  of  silex. 
travertin,  and  gypsum  precipitated  when  the  upper  lacustrine  strata  were 
formed ;  for  these  rocks  are  such  as  the  waters  of  mineral  and  thermal 
springs  might  generate. 

Cretaceous  period.  —  Although  we  have  no  proof  of  volcanic  rocks 
erupted  in  England  during  the  deposition  of  the  chalk  and  greensand,  it 
would  be  an  error  to  suppose  that  no  theatres  of  igneous  action  existed 
in  the  cretaceous  period.  M.  Virlet,  in  his  account  of  the  geology  of 
the  Morea,  p.  205,  has  clearly  shown  that  certain  traps  in  Greece,  called 
by  him  ophiolites,  are  of  this  date ;  as  those,  for  example,  which  alter- 
nate conformably  with  cretaceous  limestone  and  greensand  between  Kas- 
tri  and  Damala  in  the  Morea.  They  consist  in  great  part  of  diallage 
rocks  and  serpentine,  and  of  an  amygdaloid  with  calcareous  kernels,  and 
a  base  of  serpentine. 

In  certain  parts  of  the  Morea,  the  age  of  these  volcanic  rocks  is  es- 
tablished by  the  following  proofs ;  first,  the  lithographic  limestones  of 
the  Cretaceous  era  are  cut  through  by  trap,  and  then  a  conglomerate 
occurs,  at  Nauplia  and  other  places,  containing  in  its  calcareous  cement 
many  well-known  fossils  of  the  chalk  and  greensand,  together  with  peb- 
bles formed  of  rolled  pieces  of  the  same  ophiolite,  which  appear  in  the 
dikes  above  alluded  to. 

Period  of  Oolite  and  Lias.  —  Although  the  green  and  serpentinous 
trap  rocks  of  the  Morea  belong  chiefly  to  the  Cretaceous  era,  as  before 
mentioned,  yet  it  seems  that  some  eruptions  of  similar  rocks  began  dur- 
ing  the  Oolitic  period  ;*  and  it  is  probable,  that  a  large  part  of  the 
trappean  masses,  called  ophiolites  in  the  Apennines,  and  associated  with 
the  limestone  of  that  chain,  are  of  corresponding  age. 

That  some  part  of  the  volcanic  rocks  of  the  Hebrides,  in  our  own  coun- 
try, originated  contemporaneously  with  the  Oolite  which  they  traverse  and 
overlie,  has  been  ascertained  by  Prof.  E.  Forbes,  in  1850.  Some  of  the 
eruptions  in  Skye,  for  example,  occurred  at  the  close  of  the  Middle  and 
before  the  commencement  of  the  Upper  Oolitic  Period.f 

Trap  of  the  New  Red  Sandstone  penod. — In  the  southern  part  of 
Devonshire,  trappean  rocks  are  associated  with  New  Red  Sandstone,  and, 
according  to  Sir  H.  de  la  Beche,  have  not  been  intruded  subsequently 
into   the   sandstone,  but  were   produced  by  contemporaneous  volcanic 
action.     Some  beds  of  grit,  mingled  with  ordinary  red  marl,  resemble 
sands  ejected  from  a  crater ;  and  in  the  stratified  conglomerates  occurring 
near  Tiverton  are  many  angular  fragments  of  trap  porphyry,  some  of  them 
*  Boblaye  and  Virlet,  Morea,  p.  23. 
f  GeoL  Quart  Journ.  1851,  vol.  vii.  p.  108. 


556 


VOLCANIC  ROCKS  OF  THE 


[On.  XXXII. 


one  or  two  tons  in  weight,  intermingled  with  pebbles  of  other  rocks. 
These  angular  fragments  were  probably  thrown  out  from  volcanic  vents, 
and  fell  upon  sedimentary  matter  then  in  the  course  of  deposition.* 

Carboniferous  period.  —  Two  classes  of  contemporaneous  trap  rocks 
have  been  ascertained  by  Dr.  Fleming  to  occur  in  the  coal-field  of  the 
Forth  in  Scotland.  The  newest  of  these,  connected  with  the  higher  series 
of  coal-measures,  is  well  exhibited  along  the  shores  of  the  Forth,  in  Fife- 
*hire,  where  they  consist  of  basalt  with  olivine,  amygdaloid,  greenstone, 

Fig.  6T9. 


Eock  and  Spindle,  St  Andrew's,  as  seen  in  1888. 
a.  Unstratified  tuff.  &.  Columnar  greenstone.  c.  Stratified  tuffi 

*  De  la  Beche,  Geol.  Proceedings,  No.  41,  p.  198. 


CH.  XXXIL]  CARBONIFEROUS  PERIOD.  557 

wacke,  and  tuff.  They  appear  to  have  been  erupted  while  the  sediment- 
ary strata  were  in  a  horizontal  position,  and  to  have  suffered  the  same 
dislocations  which  those  strata  have  subsequently  undergone.  In  the 
volcanic  tuffs  of  this  age  are  found  not  only  fragments  of  limestone, 
shale,  flinty  slate,  and  sandstone,  but  also  pieces  of  coal. 

The  other  or  older  class  of  carboniferous  traps  are  traced  along  the 
south  margin  of  Stratheden,  and  constitute  a  ridge  parallel  with  the 
Ochils,  and  extending  from  Stirling  to  near  St.  Andrews.  They  consist 
almost  exclusively  of  greenstone,  becoming,  in  a  few  instances,  earthy 
and  amygdaloidal.  They  are  regularly  interstratified  with  the  sandstone, 
shale,  and  ironstone  of  the  lower  Coal-measures,  and,  on  the  East  Lo- 
mond, with  Mountain  Limestone. 

I  examined  these  trap  rocks  in  1838,  in  the  cliffs  south  of  St.  An- 
drews, where  they  consist  in  great  part,  of  stratified  tuffs,  which  are 
curved,  vertical,  and  contorted,  like  the  associated  coal-measures.  In 
the  tuff  I  found  fragments  of  carboniferous  shale  and  limestone,  and 
intersecting  veins  of  greenstone.  At  one  spot,  about  two  miles  from 
St.  Andrews,  the  encroachment  of  the  sea  on  the  cliffs  has  isolated 
several  masses  of  traps,  one  of  which  (fig.  679)  is  aptly  called  the 
"rock  and  spindle,"*  for  it  consists  of  a  pinnacle  of  tuff,  which  may 
be  compared  to  a  distaff,  and  near  the  base  is  a  mass  of  columnar 
greenstone,  in  which  the  pillars  radiate  from  a  centre,  and  appear  at 
a  distance  like  the  spokes  of  a  wheel.  The  largest  diameter  of  this 
wheel  is  about  twelve  feet,  and  the  polygonal  termina- 
tions of  the  columns  are  seen  round  the  circumference 
(or  tire,  as  it  were,  of  the  wheel),  as  in  the  accompany- 
ing figure.  I  conceive  this  mass  to  be  the  extremity  of 
a  string  or  vein  of  greenstone,  which  penetrated  the 
tuff.  The  prisms  point  in  every  direction,  because  they 
were  surrounded  on  all  sides  by  cooling  surfaces,  to 
which  they  always  arrange  themselves  at  right  angles, 


as  before  explained  (p.  484).  -wise  at  &,  fig.  679. 

A  trap  dike  was  pointed  out  to  me  by  Dr.  Fleming,  in  the  parish  of 
Flisk,  in  the  northern  part  of  Fifeshire,  which  cuts  through  the  grey 
sandstone  and  shale,  forming  the  lowest  part  of  the  Old  Red  Sandstone. 
It  may  be  traced  foi  many  miles,  passing  through  the  amygdaloidal  and 
other  traps  of  the  hill  called  Normans  Law.  In  its  course  it  affords  a 
good  exemplification  of  the  passage  from  the  trappean  into  the  plutonic, 
or  highly  crystalline  texture.  Professor  Gustavus  Rose,  to  whom  I 
submitted  specimens  of  this  dike,  finds  the  rock,  which  he  calls  dolerite, 
to  consist  of  greenish  black  augite  and  Labrador  felspar,  the  latter  being 
the  most  abundant  ingredient.  A  small  quantity  of  magnetic  iron,  per- 
haps titaniferous,  is  also  present.  The  result  of  this  analysis  is  interest- 
ing, because  both  the  ancient  and  modern  lavas  of  Etna  consist  in  like 
manner  of  augite,  Labradorite,  and  titaniferous  iron. 

*  "  The  rock,"  as  English  readers  of  Burns'  poems  may  remember,  is  a  Scotch 
term  for  distaff. 


558  SILURIAN  VOLCANIC  ROCKS.  [On.  XXXII. 

Trmp  of  the  Old  Red  Sandstone  period. — By  referring  to  the  section 
explanatory  of  the  structure  of  Forfarshire,  already  given  (p.  48),  the 
reader  will  perceive  that  beds  of  conglomerate,  No.  3,  occur  in  the  middle 
of  the  Old  Red  sandstone  system,  1, 2,  3,  4.  The  pebbles  in  these  conglom 
erates  are  sometimes  composed  of  granitic  and  quartzose  rocks,  some 
times  exclusively  of  different  varieties  of  trap,  which,  although  pur- 
posely omitted  in  the  section  referred  to,  are  often  found  either  intruding 
themselves  in  amorphous  masses  and  dikes  into  the  old  fossiliferous  tile- 
stones,  No.  4,  or  alternating  with  them  in  conformable  beds.  All  the 
different  divisions  of  the  red  sandstone,  1,  2,  3,  4,  are  occasionally  inter- 
sected by  dikes,  but  they  are  very  rare  in  Nos.  1  and  2,  the  upper  mem- 
bers of  the  group  consisting  of  red  shale  and  red  sandstone.  These 
phenomena,  which  occur  at  the  foot  of  the  Grampians,  are  repeated  in 
the  Sidlaw  Hills ;  and  it  appears  that  in  this  part  of  Scotland,  volcanic 
eruptions  were  most  frequent  in  the  earlier  part  of  the  Old  Red  sand- 
stone period. 

The  trap  rocks  alluded  to  consist  chiefly  of  felspathic  porphyry  and 
amygdaloid,  the  kernels  of  the  latter  being  sometimes  calcareous,  often 
chalcedonic,  and  forming  beautiful  agates.  We  meet  also  with  claystone, 
clinkstone,  greenstone,  compact  felspar,  and  tuff.  Some  of  these  rocks 
flowed  as  lavas  over  the  bottom  of  the  sea,  and  enveloped  quartz  pebbles 
which  were  lying  there,  so  as  to  form  conglomerates  with  a  base  of  green- 
stone, as  is  seen  in  Lumley  Den,  in  the  Sidlaw  Hills.  On  either  side  of 
the  axis  of  this  chain  of  hills  (see  section,  p.  48),  the  beds  of  massive 
trap,  and  the  tuffs  composed  of  volcanic  sand  and  ashes,  dip  regularly  to 
the  south-east  or  north-west,  conformably  with  the  shales  and  sandstones. 

Silurian  period.  —  It  appears  from  the  investigations  of  Sir  R.  Mur- 
chison  in  Shropshire,  that  when  the  lower  Silurian  strata  of  that  county 
were  accumulating,  there  were  frequent  volcanic  eruptions  beneath  the 
sea ;  and  the  ashes  and  scoria  then  ejected  gave  rise  to  a  peculiar  kind 
of  tufaceous  sandstone  or  grit,  dissimilar  to  the  other  rocks  of  the  Silu- 
rian series,  and  only  observable  in  places  where  syenitic  and  other  trap 
rocks  protrude.  These  tuffs  occur  on  the  flanks  of  the  Wrekin  and 
Caer  Caradoc,  and  contain  Silurian  fossils,  such  as  casts  of  encrinites, 
trilobites,  and  mollusca.  Although  fossiliferous,  the  stone  resembles  a 
sandy  claystone  of  the  trap  family.* 

Thin  layers  of  trap,  only  a  few  inches  thick,  alternate,  in  some  parts 
of  Shropshire  and  Montgomeryshire,  with  sedimentary  strata  of  the 
lower  Silurian  system.  This  trap  consists  of  slaty  porphyry  and  granu- 
lar felspar  rock,  the  beds  being  traversed  by  joints  like  those  in  the 
associated  sandstone,  limestone,  and  shale,  and  having  the  same  strike 
and  dip.f 

In  Radnorshire  there  is  an  example  of  twelve  bands  of  stratified  trap, 
alternating  with  Silurian  schists  and  flagstones,  in  a  thickness  of  350  feet. 
The  bedded  traps  consist  of  felspar-porphyry,  clinkstone,  and  other  va- 

*  Murchison,  Silurian  System,  &c.  p.  230.  f  Ibid.  p.  272. 


On.  XXX1U  CAMBRIAN  VOLCANIC   ROCKS.  559 

neties ,  and  the  interposed  Llandeilo  flags  are  of  sandstone  and  shale, 
with  trilobites  and  graptolites.* 

Cambrian  Volcanic  Rocks. — In  a  former  chapter  (Ch.  XXVIL  p.  447), 
we  have  seen  that  below  the  Llandeilo  and  Bala  beds  of  Lower  Silurian 
date  there  occur,  in  North  "Wales,  a  series  of  rocks  of  vast  tliickness, 
which  may  be  called  Cambrian.  The  upper  subdivision,  named  by  Pro- 
fessor Sedgwick  the  "  Festiniog  group,"  comprises,  first,  the  Arenig  Slates, 
7000  feet  thick  in  North  "Wales,  in  the  midst  of  which  dense  masses  of 
porphyry,  trap-conglomerate,  and  other  igneous  rocks,  which  are  supposed 
by  Professor  Sedgwick  to  be  of  contemporaneous  origin,  are  intercalated ; 
secondly,  the  Lingula  flags  underlying  the  former,  and  of  which  the  fossils 
were  treated  of  at  p.  448  ;  thirdly,  still  lower,  the  Bangor  group  or  Lower 
Cambrian,  in  which  bands  of  felspathic  porphyry  occur.  These  last  are, 
in  the  opinion  of  Professor  Ramsay,  intrusive  and  not  of  the  same  date  as 
the  associated  sedimentary  deposits. 

Professor  Sedgwick  has  also  described,  in  his  account  of  the  geology  of 
Cumberland,  various  trap  rocks  which  accompany  green  slates,  agreeing 
in  mineral  character  and  aspect  with  the  Arenig  Slates,  which  underlie 
all  the  fossiliferous  strata  of  Cumberland,  and  consist  of  felspathic  and 
porphyritic  rocks  and  greenstones,  occurring  not  only  in  dikes,  but  in 
conformable  beds.  Occasionally  there  is  a  passage  from  these  igneous 
rocks  to  some  of  the  green  quartzose  slates.  These  porphyries  are  sup- 
posed to  have  been  produced  contemporaneously  with  the  stratified  chlo- 
ritic  slates  by  submarine  eruptions  oftentimes  repeated,  the  materials  of  the 
slates  having  been  supplied,  in  part  at  least,  from  the  same  source.f 

*  Murehison,  Silurian  System,  dzc.  p.  825. 
f  Geoi  Trans.  2d  series,  voL  iv.  p.  55. 


560  PLUTONIC  ROCKS.  [On.  XXXIII 


CHAPTER  XXXIII. 

PLUTONIC   ROCKS  —  GRANITE. 

General  aspect  of  granite — Decomposing  into  spherical  masses — Rude  columnar 
structure — Analogy  and  difference  of  volcanic  and  plutonic  formations — Mine- 
rals in  granite,  and  their  arrangement — Graphic  and  porphyritic  granite  — 
Mutual  penetration  of  crystals  of  quartz  and  felspar — Occasional  minerals — 
Syenite — Syenitic,  talcose,  and  schorly  granites — Eurite — Passage  of  granite 
into  trap — Examples  near  Christiania  and  in  Aberdeenshire — Analogy  in  com- 
position of  trachyte  and  granite  —  Granite  veins  in  Glen  Tilt,  Cornwall,  the 
Valorsine,  and  other  countries — Different  composition  of  veins  from  main  body 
of  granite  —  Metalliferous  veins  in  strata  near  their  junction  with  granite  — 
Apparent  isolation  of  nodules  of  granite — Quartz  veins  —  Whether  plutonic 
rocks  are  ever  overlying  —  Their  exposure  at  the  surface  due  to  denudation. 

THE  plutonic  rocks  may  be  treated  of  next  in  order,  as  they  are  most 
nearly  allied  to  the  volcanic  class  already  considered.  I  have  described, 
in  the  first  chapter,  these  plutonic  rocks  as  the  unstratified  division  of 
the  crystalline  or  hypogene  formations,  and  have  stated  that  they  differ 
from  the  volcanic  rocks,  not  only  by  their  more  crystalline  texture,  but 
also  by  the  absence  of  tuffs  and  breccias,  which  are  the  products  of  erup- 
tions at  the  earth's  surface,  or  beneath  seas  of  inconsiderable  depth. 
They  differ  also  by  the  absence  of  pores  or  cellular  cavities,  to  which  the 
expansion  of  the  entangled  gases  gives  rise  in  ordinary  lava.  From  these 
and  other  peculiarities,  it  has  been  inferred,  that  the  granites  have  been 
formed  at  considerable  depths  in  the  earth,  and  have  cooled  and  crystal- 
lized slowly  under  great  pressure,  where  the  contained  gases  could  not 
expand.  The  volcanic  rocks,  on  the  contrary,  although  they  also  have 
risen  up  from  below,  have  cooled  from  a  melted  state  more  rapidly  upon 
or  near  the  surface.  From  this  hypothesis  of  the  great  depth  at  which 
the  granites  originated,  has  been  derived  the  name  of  "Plutonic  rocks." 
The  beginner  will  easily  conceive  that  the  influence  of  subterranean  heat 
may  extend  downwards  from  the  crater  of  every  active  volcano  to  a  great 
depth  below,  perhaps  several  miles  or  leagues,  and  the  effects  which  are 
produced  deep  in  the  bowels  of  the  earth  may,  or  rather  must  be,  dis- 
tinct ;  so  that  volcanic  and  plutonic  rocks,  each  different  in  texture,  and 
sometimes  even  in  composition,  may  originate  simultaneously,  the  one 
at  the  surface,  the  other  far  beneath  it. 

By  some  writers,  all  the  rocks  now  under  consideration  have  been 
comprehended  under  the  name  of  granite,  which  is,  then,  understood  to 
embrace  a  large  family  of  crystalline  and  compound  rocks,  usually  found 
underlying  all  other  formations ;  whereas  we  have  seen  that  trap  very 
commonly  overlies  strata  of  different  ages.  Granite  often  preserves  a 
very  uniform  character  throughout  a  wide  range  of  territory,  forming 
hills  of  a  peculiar  rounded  form,  usually  clad  with  a  scanty  vegetatioa 


CH.  XXXIII. ] 


GENERAL  ASPECT   OF   GRANITE. 


561 


The  surface  of  the  rock  is  for  the  most  part  in  a  crumbling  state,  and 
he  hills  are  often  surmounted  by  piles  of  stones  like  the  remains  of  a 
stratified  mass,  as  in  the  annexed  figure,  and  sometimes  like  heaps  of 
boulders,  for  which  they  have  been  mistaken.  The  exterior  of  these 

Fig.  681. 


Mass  of  granite  near  the  Sharp  Tor,  Cornwall. 

Btones,  originally  quadrangular,  acquires  a  rounded  form  by  the  action 
of  air  and  water,  for  the  edges  and  angles  waste  away  more  rapidly  than 
the  sides.  A  similar  spherical  structure  has  already  been  described  as 
characteristic  of  basalt  and  other  volcanic  formations,  and  it  must  be 
referred  to  analogous  causes,  as  yet  but  imperfectly  understood. 

Although  it  is  the  general  peculiarity  of  granite  to  assume  no  definite 
shapes,  it  is  nevertheless  occasionally  subdivided  by  fissures,  so  as  to 
assume  a  cuboidal,  and  even  a  columnar  structure.  Examples  of  these 
appearances  may  be  seen  near  the  Land's  End,  in  Cornwall.  (See 
figure  682.) 

Fig.  6S2. 


Granite  having  a  cuboidal  and  rude  columnar  structure,  Land's  End,  Cornwall. 

The  plutonic  formations  also  agree  with  the  volcanic,  in  having  veins 
•>r  ramifications  proceeding  from  central  masses  into  the  adjoining  rocks, 

36 


562  MINERAL  COMPOSITION  OF   GRANITE.         [Cn.  XXXIII 

aiid  causing  alterations  in  these  last,  which  will  be  presently  described, 
They  also  resemble  trap  in  containing  no  organic  remains;  but  they 
differ  in  being  more  uniform  in  texture,  whole  mountain  masses  of  inde- 
finite extent  appearing  to  have  originated  under  conditions  precisely 
similar.  They  also  differ  in  never  being  scoriaceous  or  amygdaloidal, 
and  never  forming  a  porphyry  with  an  uncrystalline  base,  or  alternating 
with  tuffs.  Nor  do  they  form  conglomerates,  although  there  is  sometimes 
an  insensible  passage  from  a  fine  to  a  coarse-grained  granite,  and  occa- 
sionally patches  of  a  fine  texture  are  imbedded  in  a  coarser  variety. 

Felspar,  quartz,  and  mica  are  usually  considered  as  the  minerals 
essential  to  granite,  the  felspar  being  most  abundant  in  quantity,  and 
the  proportion  of  quartz  exceeding  that  of  mica.  These  minerals  are 
united  in  what  is  termed  a  confused  crystallization ;  that  is  to  say,  there 
is  no  regular  arrangement  of  the  crystals  in  granite,  as  in  gneiss  (see 
fig.  704,  p.  590),  except  in  the  variety  termed  graphic  granite,  which 
occurs  mostly  in  granitic  veins.  This  variety  is  a  compound  of  felspar 
and  quartz,  so  arranged  as  to  produce  an  imperfect  laminar  structure. 
The  crystals  of  felspar  appear  to  have  been  first  formed,  leaving  between 

Fig.  683.  Jig.  684. 


Graphic  granite. 

Fig.  683.  Section  parallel  to  the  laminae. 
Fig.  684.  Section  transverse  to  the  laminae. 

them  the  space  now  occupied  by  the  darker-colored  quartz.  This  min- 
eral, when  a  section  is  made  at  right  angles  to  the  alternate  plates  of 
felspar  and  quartz,  presents  broken  lines,  which  have  been  compared  to 
Hebrew  characters.  The  variety  of  granite  called  by  the  French 
Pegmatite,  which  is  a  mixture  of  quartz  and  common  felspar,  usually 
with  some  small  admixture  of  white  silvery  mica,  often  passes  into 
graphic  granite. 

As  a  general  rule,  quartz,  in  a  compact  or  amorphous  state,  forms 
a  vitreous  mass,  serving  as  the  base  in  which  felspar  and  mica  have 
crystallized ;  for  although  these  minerals  are  much  more  fusible  than 
silex,  they  have  often  imprinted  their  shapes  upon  the  quartz.  This 
fact,  apparently  so  paradoxical,  has  given  rise  to  much  ingenious  specu- 
lation. We  should  naturally  have  anticipated  that,  during  the  cooling 
of  the  mass,  the  flinty  portion  would  be  the  first  to  consolidate  ;  and 
that  the  different  varieties  of  felspar,  as  well  as  garnets  and  tourmalines, 
being  more  easily  liquefied  by  heat,  would  be  the  last.  Precisely  the 


G*n.  XXXIII.]  PORPHYRITIC   GRANITE.  563 

reverse  has  taken  place  in  the  passage  of  most  granite  aggregates  from 
a  fluid  to  a  solid  state,  crystals  of  the  more  fusible  minerals  being  found 
enveloped  in  hard,  transparent,  glassy  quartz,  which  has  often  taken 
very  faithful  casts  of  each,  so  as  to  preserve  even  the  microscopically 
minute  striations  on  the  surface  of  prisms  of  tourmaline.  Various  ex- 
planations of  this  phenomenon  have  been  proposed  by  MM.  de  Beau- 
mont, Fournet,  and  Durocher.  They  refer  to  M.  Gaudin's  experiments 
on  the  fusion  of  quartz,  which  show  that  silex,  as  it  cools,  has  the  prop- 
erty of  remaining  in  a  viscous  state,  whereas  alumina  never  does.  This 
"  gelatinous  flint"  is  supposed  to  retain  a  considerable  degree  of  plas- 
ticity long  after  the  granitic  mixture  has  acquired  a  low  temperature ; 
and  M.  E.  de  Beaumont  suggests,  that  electric  action  may  prolong  the 
duration  of  the  viscosity  of  silex.  Occasionally,  however,  we  find  the 
quartz  and  felspar  mutually  imprinting  their  forms  on  each  other,  afford- 
ing evidence  of  the  simultaneous  crystallization  of  both.* 

It  may  here  be  remarked  that  ordinary  granite,  as  well  as  syenite 
and  eurite,  usually  contains  two  kinds  of  felspar ;  1st,  the  common,  or 
orthoclase,  in  which  potash  is  the  prevailing  alkali,  and  this  generally 
occurs  in  large  crystals  of  a  white  or  flesh  color ;  and  2dly,  felspar  in 
smaller  crystals,  in  which  soda  predominates,  usually  of  a  dead  white  or 
spotted,  and  striated  like  albite,  but  not  the  same  in  composition.! 

Porphyritic  granite. — This  name  has  been  sometimes  given  to  that 
variety  in  which  large  crystals  of  common  felspar,  sometimes  more  than 
3  inches  in  length,  are  scattered  through  an  ordinary  base  of  granite. 
An  example  of  this  texture  may  be  seen  in  the  granite  of  the  Land's 
End,  in  Cornwall  (fig.  685).  The  two  larger  prismatic  crystals  in  this 

Fig.  685. 


Porphyritic  granite.    Land's  End,  Cornwall. 

drawing  represent  felspar,  smaller  crystals  of  which  are  also  seen,  similar 
in  form,  scattered  through  the  base.  In  this  base  also  appear  black 
specks  of  mica,  the  crystals  of  which  have  a  more  or  less  perfect  hex- 
agonal outline.  The  remainder  of  the  mass  is  quartz,  the  translucency 
of  which  is  strongly  contrasted  to  the  opaqueness  of  the  white  felspar 
and  black  mica.  But  neither  the  transparency  of  the  quartz,  nor  the 
silvery  lustre  of  the  mica,  can  be  expressed  in  the  engraving. 

*  Bulletin,  2d  sfcrie,  iv.  1304;  and  Archiac,  Hist,  des  Progres  de  Geol.,  i.  38. 
t  Delesse,  Ann.  des  Mines,  1852,  t,  iii.  p.  409,  and  1848,  t  xiii.  p.  675. 


564  PASSAGE   OF  [Oa  XXXIIL 

The  uniform  mineral  character  of  large  masses  of  granite  seems  tc 
indicate  that  large  quantities  of  the  component  elements  were  thoroughly 
mixed  up  together,  and  then  crystallized  under  precisely  similar  condi- 
tions. There  are,  however,  many  accidental,  or  "  occasional,"  minerals, 
as  they  are  termed,  which  belong  to  granite.  Among  these  black  schorl 
or  tourmaline,  actinolite,  zircon,  garnet,  and  fluor  spar,  are  not  uncom- 
mon ;  but  they  are  too  sparingly  dispersed  to  modify  the  general  aspect 
of  the  rock.  They  show,  nevertheless,  that  the  ingredients  were  not 
everywhere  exactly  the  same ;  and  a  still  greater  variation  may  be  traced 
in  the  ever-varying  proportions  of  the  felspar,  quartz,  and  mica. 

Syenite. — When  hornblende  is  the  substitute  for  mica,  which  is  very 
commonly  the  case,  the  rock  becomes  Syenite  :  so  called  from  the  cele- 
brated ancient  quarries  of  Syene  in  Egypt.  It  has  all  the  appearance  of 
ordinary  granite,  except  where  mineralogically  examined  in  hand  specimens, 
and  is  fully  entitled  to  rank  as  a  geological  member  of  the  same  plutonic 
family  as  granite.  Syenite,  however,  after  maintaining  the  granitic  char- 
acter throughout  extensive  regions,  is  not  uncommonly  found  to  lose  its 
quartz,  and  to  pass  insensibly  into  syenitic  greenstone,  a  rock  of  the  trap 
family.  Werner  considered  syenite  as  a  binary  compound  of  felspar  and 
hornblende,  and  regarded  quartz  as  merely  one  of  its  occasional  minerals 

Syenitic  granite. — The  quadruple  compound  of  quartz,  felspar,  mica, 
and  hornblende,  may  be  so  termed.  This  rock  occurs  in  Scotland  and  in 
Guernsey. 

Talcose  granite,  or  Protogine  of  the  French,  is  a  mixture  of  felspar, 
quartz,  and  talc.  It  abounds  in  the  Alps,  and  in  some  parts  of  Cornwall, 
producing  by  its  decomposition  the  china  clay,  more  than  12,000  tons  of 
which  are  annually  exported  from  that  country  for  the  potteries.* 

Schorl  rock,  and  schorly  granite. — The  former  of  these  is  an  aggregate 
of  schorl,  or  tourmaline,  and  quartz.  When  felspar  and  mica  are  also 
present,  it  may  be  called  schorly  granite.  This  kind  of  granite  is  com- 
paratively rare. 

Eurite. — A  rock  in  which  all  the  ingredients  of  granite  are  blended 
into  a  finely  granular  mass.  When  crystalline,  it  is  seen  to  contain 
crystals  of  quartz,  mica,  common  felspar,  and  soda  felspar.  When  there 
is  no  mica,  and  when  common  felspar  predominates,  so  as  to  give  it  a 
white  color,  it  becomes  a  felspathic  granite,  called  "  whitestone"  (Weis- 
stein)  by  Werner,  or  Leptynite  by  the  French,  in  which  microscopic 
crystals  of  garnet  are  often  present. 

All  these  and  other  varieties  of  granite  pass  into  certain  kinds  of  trap, 
a  circumstance  which  affords  one  of  many  arguments  in  favor  of  what  is 
now  the  prevailing  opinion,  that  the  granites  are  also  of  igneous  origin. 
The  contrast  of  the  most  crystalline  form  of  granite,  to  that  of  the  most 
common  and  earthy  trap,  is  undoubtedly  great ;  but  each  member  of  the 
volcanic  class  is  capable  of  becoming  porphyritic,  and  the  base  of  the 
porphyry  may  be  more  and  more  crystalline,  until  the  mass  passes  to  the 
kind  of  granite  most  nearly  allied  in  mineral  composition. 
*  Boase  on  Primary  Geology,  p.  16. 


CH.  XXXIIL]  GRANITE  INTO  TRAP.  565 

The  minerals  which  constitute  alike  the  granitic  and  volcanic  rocks 
consist,  almost  exclusively,  of  seven  elements;  namely,  silica,  alumina, 
magnesia,  lime,  soda,  potash,  and  iron  (see  Table,  p.  475) ;  and  these  may 
sometimes  exist  in  about  the  same  proportions  in  a  porous  lava,  a  compact 
trap,  or  a  crystalline  granite.  It  may  perhaps  be  found,  on  further  ex- 
amination— for  on  this  subject  we  have  yet  much  to  learn — that  the  pres- 
ence of  these  elements  in  certain  proportions  is  more  favorable  than  in 
others  to  their  assuming  a  crystalline  or  true  granitic  structure  ;  but  it  is 
also  ascertained  by  experiment,  that  the  same  materials  may,  under  differ- 
ent circumstances,  form  very  different  rocks.  The  same  lava,  for  example, 
may  be  glassy,  or  scoriaceous,  or  stony,  or  porphyritic,  according  to  the 
more  or  less  rapid  rate  at  which  it  cools ;  and  some  trachytes  and  sye- 
nitic-greenstones  may  doubtless  form  granite  and  syenite,  if  the  crystal- 
lization take  place  slowly. 

It  has  also  been  suggested  that  the  peculiar  nature  and  structure  of 
granite  may  be  due  to  its  retaining  in  it  that  water  which  is  seen  to 
escape  from  lavas  when  they  cool  slowly,  and  consolidate  in  the  atmo- 
sphere. Boutigny's  experiments  have  shown  that  melted  matter,  at  a 
white  heat,  requires  to  have  its  temperature  lowered  before  it  can  va- 
pourize  water ;  and  such  discoveries,  if  they  fail  to  explain  the  manner 
in  which  granites  have  been  formed,  serve  at  least  to  remind  us  of  the 
entire  distinctness  of  the  conditions  under  which  plutonic  and  volcanic 
rocks  must  be  produced.* 

It  would  be  easy  to  multiply  examples  and  authorities  to  prove  the 
gradation  of  the  granitic  into  the  trap  rocks.  On  the  western  side  of 
the  fiord  of  Christiania,  in  Norway,  there  is  a  large  district  of  trap, 
chiefly  greenstone-porphyry,  and  syenitic-greenstone,  resting  on  fossilife- 
rous  strata.  To  this,  on  its  southern  limit,  succeeds  a  region  equally 
extensive  of  syenite,  the  passage  from  the  volcanic  to  the  plutonic  rock 
being  so  gradual  that  it  is  impossible  to  draw  a  line  of  demarcation  be- 
tween them. 

"The  ordinary  granite  of  Aberdeenshire,"  says  Dr.  MacCulloch,  "is 
the  usual  ternary  compound  of  quartz,  felspar,  and  mica;  but  some- 
times hornblende  is  substituted  for  the  mica.  But  in  many  places  a 
variety  occurs  which  is  composed  simply  of  felspar  and  hornblende ;  and 
in  examining  more  minutely  this  duplicate  compound,  it  is  observed  in 
some  places  to  assume  a  fine  grain,  and  at  length  to  become  undistin- 
guishable  from  the  greenstones  of  the  trap  family.  It  also  passes  in 
the  same  uninterrupted  manner  into  a  basalt,  and  at  length  into  a  soft 
claystone,  with  a  schistose  tendency  on  exposure,  in  no  respect  differing 
from  those  of  the  trap  islands  of  the  western  coast.  The  same 
author  mentions,  that  in  Shetland,  a  granite  composed  of  hornblende, 
mica,  felspar,  and  quartz,  graduates  in  an  equally  perfect  manner  into 
basalif 

In  Hungary,  there  are  varieties  of  trachyte,  which,  geologically 

*  E.  de  Beaumont,  Bulletin,  vol.  iv.  2d  ser.  pp.  1318  and  1820. 
*       f  Syst.  of  GeoL  voL  i.  pp.  157,  158. 


566 


BOCKS  ALTERED   BY 


[Cn.  XXXIII 


ing,  are  of  modern  origin,  in  which  crystals,  not  only  of  mica,  but  of 
quartz,  are  common,  together  with  felspar  and  hornblende.  It  is  easy 
to  conceive  how  such  volcanic  masses  may,  at  a  certain  depth  from  the 
surface,  pass  downwards  into  granite. 

I  have  already  hinted  at  the  close  analogy  in  the  forms  of  certain 
granitic  and  trappean  veins ;  and  it  will  be  found  that  strata  penetrated 
by  plutonic  rocks  have  suffered  changes  very  similar  to  those  exhibited 
near  the  contact  of  volcanic  dikes.  Thus,  in  Glen  Tilt,  in  Scotland,  al- 
ternating strata  of  limestone  and  argillaceous  schist  come  in  contact  with 
a  mass  of  granite.  The  contact  does  not  take  place  as  might  have  been 
looked  for,  if  the  granite  had  been  formed  there  before  the  strata  were 
deposited,  in  which  case  the  section  would  have  appeared  as  in  fig.  686  ; 
but  the  union  is  as  represented  in  fig.  687,  the  undulating  outline  of  the 

Fig.  686.  Fig.  687. 


Junction  of  granite  and  argillaceous  schist  in  Glen 
Tilt.    (MacCulloch.)* 


(MacCulloch.)* 

granite  intersecting  d  inherent  strata,  and  occasionally  intruding  itself  in 
tortuous  veins  into  the  beds  of  clay-slate  and  limestone,  from  which  it 
differs  so  remarkably  in  composition.  The  limestone  is  sometimes 
changed  in  character  by  the  proximity  of  the  granitic  mass  or  its  veins, 
and  acquires  a  more  compact  texture,  like  that  of  hornstone  or  chert, 
with  a  splintery  fracture,  and  effervescing  feebly  with  acids. 

The  annexed  diagram  (fig.  688)  represents  another  junction,  in  the 
same  district,  where  the  granite  sends  forth  so  many  veins  as  to  reticu- 
late the  limestone  and  schist,  the  veins  diminishing  towards  their  termi- 
nation to  the  thickness  of  a  leaf  of  paper  or  a  thread.  In  some  places 
fragments  of  granite  appear  entangled,  as  it  were,  in  the  limestone,  and 
are  not  visibly  connected  with  any  larger  mass;  while  sometimes,  on 
the  other  hand,  a  lump  of  the  limestone  is  found  in  the  midst  of  the 
granite.  The  ordinary  colour  of  the  limestone  of  Glen  Tilt  is  lead  blue, 
and  its  texture  large-grained  and  highly  crystalline ;  but  where  it  ap- 
proximates to  the  granite,  particularly  where  it  is  penetrated  by  the 
smaller  veins,  the  crystalline  texture  disappears,  and  it  assumes  an  ap- 
pearance exactly  resembling  that  of  hornstone.  The  associated  argilla- 
ceous schist  often  passes  into  hornblende  slate,  where  it  approaches  very 
near  to  the  granite,  f 

»  Geol.  Trans.,  1st  series,  vol.  iii.  pi.  21. 

f  MacCulloch,  Geol.  Trans.,  vol.  iii.  p.  259. 


CH.  XXXIII.] 


GRANITE  VEINS. 
Kg.  633. 


567 


Junction  of  granite  and  limestone  in  Glen  Tilt.    (MacCulloch.) 


Fig.  689. 


The  conversion  of  the  limestone  in  these  and  many  other  instances 
into  a  siliceous  rock,  effervescing  slowly  with  acids,  would  be  difficult 
of  explanation,  were  it  not  ascertained  that  such  limestones  are  always 
impure,  containing  grains  of  quartz,  mica,  or  felspar  disseminated 
through  them.  The  elements  of  these  minerals,  when  the  rock  has 
been  subjected  to  great  heat,  may  have  been 
fused,  and  so  spread  more  uniformly  through 
the  whole  mass. 

In  the  plutonic,  as  in  the  volcanic  rocks, 
there  is  every  gradation  from  a  tortuous  vein 
to  the*  most  regular  form  of  a  dike,  such  as 
intersect  the  tuffs  and  lavas  of  Vesuvius  and 
Etna.  Dikes  of  granite  may  be  seen,  among 
other  places,  on  the  southern  flank  of  Mount 
Battock,  one  of  the  Grampians,  the  opposite 
walls  sometimes  preserving  an  exact  paral- 
lelism for  a  considerable  distance. 

As  a  general  rule,  however,  granite  veins 
Granite  veins  traversing  clay  slate    in  all  quarters  of  the  globe  are  ni ore  sinuous 
Hope*Mountain'  Cape  of  Goo<i   in  their  course  than  those  of  trap.     They 
present  similar  shapes  at  the  most  northern 

point  of  Scotland,  and  the  southernmost  extremity  of  Africa,  as  the 
annexed  drawings  will  show. 

*  Capt.  B.  Hall,  Trans.  Roy.  Soc.  Edin.,  vol.  vii. 


568 


MINERAL  STRUCTURE   OF 


[On.  XXXIII 


It  is  not  uncommon  for  one  set  of  granite  veins  to  intersect  another ; 
and  sometimes  there  are  three  sets,  as  in  the  environs  of  Heidelberg, 
where  the  granite  on  the  banks  of  the  river  Necker  is  seen  to  consist  of 
three  varieties,  differing  in  colour,  grain,  and  various  peculiarities  of 

mineral  composition.  One  of  these, 
which  is  evidently  the  second  in 
age,  is  seen  to  cut  through  an  older 
granite;  and  another,  still  newer, 
traverses  both  the  second  and  the 
first. 

In  Shetland  there  are  two  kinds 
of  granite.  One  of  them  composed 
of  hornblende,  mica,  felspar,  and 
quartz,  is  of  a  dark  color,  and  is 
seen  underlying  gneiss.  The  other 
is  a  red  granite,  which  penetrates 
the  dark  variety  everywhere  in 
veins.* 

The  accompanying  sketches  will  explain  the  manner  in  which  granite 
veins  often  ramify  and  cut  each  other  (figs.  690  and  691).  They  repre- 

Fig.  691. 


Granite  veins  traversing  gneiss,  Capo  Wrath. 


Granite  veins  traversing  gneiss,  at  Cape  Wrath,  in  Scotland.    (MacCulloch.) 

sent  the  manner  in  which  the  gneiss  at  Cape  "Wrath,  in  Sutherlandshire, 
is  intersected  by  veins.  Their  light  'colour,  strongly  contrasted  with 
that  of  the  hornblende-schist,  here  associated  with  the  gneiss,  renders 
them  very  conspicuous. 

Granite  very  generally  assumes  a  finer  grain,  and  undergoes  a  change 
in  mineral  composition,  in  the  veins  which  it  sends  into  contiguous  rocks. 
Thus,  according  to  Professor  Sedgwick,  the  main  body  of  the  Cornish 
granite  is  an  aggregate  of  mica,  quartz,  and  felspar  ;  but  the  veins  are 
sometimes  without  mica,  being  a  granular  aggregate  of  quartz  and  fel- 
spar. In  other  varieties  quartz  prevails  to  the  almost  entire  exclusion 
both  of  felspar  and  mica  j  in  others,  the  mica  and  quartz  both  disappear. 
and  the  vein  is  simply  composed  of  white  granular  felspar.  J 


*  MacCulloch,  Syst.  of  Geol.,  vol.  i.,  p.  58.          f  Western  Islands,  pi.  31. 
J  On  Geol.  of  Cornwall,  Camb.  Trans.,  vol.  i.  p.  124. 


CH.  XXXIII.  ] 


GRANITE   IN  VEINS. 


569 


Fig.  692  is  a  sketch  of  a  group  of  granite  veins  in  Cornwall,  given 
by  Messrs.  Von  Oeynhausen  and  Von  Dechen.*     The  main  body  of  the 


Fig.  692. 


Granite  -veins  passing  through  hornblende  slate,  Carnsilyer  Cove,  Cornwall. 

granite  here  is  of  a  porphyritic  appearance,  with  large  crystals  of  fel- 
spar ;  but  in  the  veins  it  is  fine  grained,  and  without  these  large  crystals. 
The  general  height  of  the  veins  is  from  16  to  20  feet,  but  some  are  much 
higher. 

In  the  Valorsine,  a  valley  not  far  from  Mont  Blanc  in  Switzerland,  an 
ordinary  granite,  consisting  of  felspar,  quartz,  and  mica,  sends  forth  veins 
into  a  talcose  gneiss  (or  stratified  protogine),  and  in  some  places  lateral 
ramifications  are  thrown  off  from  the  principal  veins  at  right  angles  (see 
fig.  693),  the  veins,  especially  the  minute  ones,  being  finer  grained  than 
the  granite  in  mass. 

Fig.  698. 


Veins  of  granite  in  talcose  gneiss.    (L.  A  Necker.) 

It  is  here  remarked,  that  the  schist  and  granite,  as  they  approach, 
seem  to  exercise  a  reciprocal  influence  on  each  other,  for  both  undergo  a 
modification  of  mineral  character.  The  granite,  still  remaining  unstra- 
tified7  becomes  charged  with  green  particles;  and  the  talcose  gneiss 
assumes  a  granitiform  structure  without  losing  its  stratification.f 

*  Phil.  Mag.  and  Annals,  No.  27,  new  series,  March,  1829. 
f  Necker,  sur  de  Val.  de  Valorsine,  Me'm.  de  la  Soc.  de  Phys.  de  Geneve,  1828. 
I  visited,  in  1832,  the  spot  referred  to  in  fig.  693. 


570  ISOLATED   MASSES   OF   GRANITE.  [Cn.  XXXIIL 

Professor  Keilhau  drew  my  attention  to  several  localities  in  the 
country  near  Christiania,  where  the  mineral  character  of  gneiss  appears 
to  have  been  affected  by  a  granite  of  much  newer  origin,  for  some 
distance  from  the  point  of  contact.  The  gneiss,  without  losing  its 
laminated  structure,  seems  to  have  become  charged  with  a  larger 
quantity  of  felspar,  and  that  of  a  redder  colour,  than  the  felspar  usually 
belonging  to  the  gneiss  of  Norway. 

Granite,  syenite,  and  those  porphyries  which  have  a  granitiform 
structure,  in  short  all  plutonic  rocks,  are  frequently  observed  to  contain 
metals,  at  or  near  their  junction  with  stratified  formations.  On  the 
other  hand,  the  veins  which  traverse  stratified  rocks  are,  as  a  general  law, 
more  metalliferous  near  such  junctions  than  in  other  positions.  Hence 
it  has  been  inferred  that  these  metals  may  have  been  spread  in  a  gaseous 
form  through  the  fused  mass,  and  that  the  contact  of  another  rock,  in 
a  different  state  of  temperature,  or  sometimes  the  existence  of  rents  in 
other  rocks  in  the  vicinity,  may  have  caused  the  sublimation  of  the  me- 
tals.* 

There  are  many  instances,  as  at  Markerud,  near  Christiania,  in  Nor- 
way, where  the  strike  of  the  beds  has  not  been  deranged  throughout  a 
large  area  by  the  intrusion  of  granite,  both  in  large  masses  and  in  veins. 
This  fact  is  considered  by  some  geologists  to  militate  against  the  theory 
of  the  forcible  injection  of  granite  in  a  fluid  state.  But  it  may  be  stated 
in  repiy,  tnat  ramifying  dikes  of  trap  also,  which  almost  all  now  admit 
to  have  been  once  fluid,  pass  through  the  same  fossiliferous  strata,  near 
Christiania,  without  deranging  their  strike  or  dip.f 

The  real  or  apparent  isolation  of  large  or  small  masses  of  granite  de- 
tached from  the  main  body,  as  at  a  £,  fig.  694  and  above,  fig.  688,  and 

Fig.  694 


General  view  of  junction  of  granite,  and  schist  of  the  Valorsine. 
(L.  A.  Necker.) 

a,  fig.  693,  has  been  thought  by  some  writers  to  be  irreconcilable  with 
the  doctrine  usually  taught  respecting  veins ;  but  many  of  them  may, 
in  fact,  be  sections  of  root-shaped  prolongations  of  granite ;  while,  in 
other  cases,  they  may  in  reality  be  detached  portions  of  rock  having  the 
plutonic  structure.  For  there  may  have  been  spots  in  the  midst  of  the 
invaded  strata,  in  which  there  was  an  assemblage  of  materials  more  fusi- 
ble than  the  rest,  or  more  fitted  to  combine  readily  into  some  form  of 
granite. 

*  Necker,  Proceedings  of  Geol.  Soc.,  No.  26,  p.  392. 

f  See  Keilhau's  Gaoa  Norvegica;  Christiania,  1838. 


CH.  XXXIII.  ] 


CONFORMABLE   PORPHYRIES. 


671 


Veins  of  pure  quartz  are  often  found  in  granite,  as  in  many  stratified 
rocks,  but  they  are  not  traceable,  like  veins  of  granite  or  trap,  to  large 
bodies  of  rock  of  similar  composition.  They  appear  to  have  been  cracks, 
into  which  siliceous  matter  was  infiltered.  Such  segregation,  as  it  is 
called,  can  sometimes  be  shown  to  have  clearly  taken  place  long  subse- 
quently to  the  original  consolidation  of  the  containing  rock.  Thus,  for 
example,  I  observed  in  the  gneiss  of  Tronstad  Strand,  near  Drammen,  in 
Norway,  the  annexed  section  on  the  beach.  It  appears  that  the  alternat- 
ing strata  of  whitish  granitiform  gneiss,  and  black  hornblende-schist,  were 
first  cut  through  by  a  greenstone  dike,  about  2£  feet  wide;  then  the 
crack  a  b  passed  through  all  these  rocks,  and  was  filled  up  with  quartz. 
The  opposite  walls  of  the  vein  are  in  some  parts  encrusted  with  transpa- 
rent crystals  of  quartz,  the  middle  of  the  vein  being  filled  up  with  com- 
mon opaque  white  quartz. 

Fig.  695. 


Gnt-i". 


Gneiss. 


We  have  seen  that  the  volca- 
nic formations  have  been  called 
overlying,  because  they  not  only 
penetrate  others,  but  spread 
over  them.  Mr.  Necker  has 
proposed  to  call  the  granites 
the  underlying  igneous  rocks, 
and  the  distinction  here  indi- 
cated is  highly  characteristic. 
It  was  indeed  supposed  by  some 

a,  &.  Quartz  rein  passing  through  gneiss  and  green-    of  the  earlier  observers,  that  the 
stone,  Tronstad  Strand,  near  Christiania.         *  ^^   of  Christiania,   in   Nor. 

way,  was  intercalated  in  mountain  masses  between  the  primary  or  paleo- 
zoic strata  of  that  country,  so  as  to  overlie  fossiliferous  shale  and  lime- 
stone. But  although  the  granite  sends  veins  into  these  fossiliferous  rocks, 
and  is  decidedly  posterior  in  origin,  its  actual  superposition  in  mass  has 
been  disproved  by  Professor  Keilhau,  whose  observations  on  this  contro- 
verted point  I  had  opportunities  in  1837  of  verifying.  There  are,  how- 
ever, on  a  smaller  scale,  certain  beds  of  euritic  porphyry,  some  a  few 
feet,  others  many  yards  in  thickness,  which  pass  into  granite,  and  deserve 
perhaps  to  be  classed  as  plutonic  rather  than  trappean  rocks,  which  may 
truly  be  described  as  interposed  conformably  between  fossiliferous  strata, 
as  the  porphyries  (ac,  fig.  696),  which  divide  the  bituminous  shales  and 


Euritic  porphyry  alternating  with  primary  fossiliferous  strata, 
near  Christiania. 

argillaceous  limestones,  ff.     But  some  of  these  same  porphyries  are 
partially  unconformable,  as  b,  and  may  lead  us  to  suspect  that  the  others 


572  GRANITE   ROCKS.  [Cir.  XXXIII. 

also,  notwithstanding  their  appearance  of  interstratification,  have  been 
forcibly  injected.  Some  of  the  porphyritic  rocks  above  mentioned  are 
highly  quartzose,  others  very  felspathic.  In  proportion  as  the  masses 
are  more  voluminous,  they  become  more  granitic  in  their  texture,  less 
conformable,  and  even  begin  to  send  forth  veins  into  contiguous  strata. 
In  a  word,  we  have  here  a  beautiful  illustration  of  the  intermediate  gra- 
dations between  volcanic  and  plutonic  rocks,  not  only  in  their  mineral- 
ogical  composition  and  structure,  but  also  in  their  relations  of  position 
to  associated  formations.  If  the  term  overlying  can  in  this  instance  be 
applied  to  a  plutonic  rock,  it  is  only  in  proportion  as  that  rock  begins  to 
acquire  a  trappean  aspect. 

It  has  been  already  hinted  that  the  heat,  which  in.  every  active  volca- 
no extends  downwards  to  indefinite  depths,  must  produce  simultaneously 
very  different  effects  near  the  surface,  and  far  below  it j  and  we  cannot 
suppose  that  rocks  resulting  from  the  crystallizing  of  fused  matter  under 
a  pressure  of  several  thousand  feet,  much  less  miles,  of  the  earth's  crust 
can  resemble  those  formed  at  or  near  the  surface.  Hence  the  production 
at  great  depths  of  a  class  of  rocks  analogous  to  the  volcanic,  and  yet 
differing  in  many  particulars,  might  also  have  been  predicted,  even  had 
we  no  plutonic  formations  to  account  for.  How  well  these  agree,  both 
in  their  positive  and  negative  characters,  with  the  theory  of  their  deep 
subterranean  origin,  the  student  will  be  able  to  judge  by  considering  the 
descriptions  already  given. 

It  has,  however,  been  objected,  that  if  the  granitic  and  volcanic  rocks 
were  simply  different  parts  of  one  great  series,  we  ought  to  find  in  moun- 
tain chains  volcanic  dikes  passing^lipwards  into  lava,  and  downwards  into 
granite.  But  we  may  answer,  that  our  vertical  sections  are  usually  of 
small  extent ;  and  if  we  find  in  certain  places  a  transition  from  trap  to 
porous  lava,  and  in  others  a  passage  from  granite  to  trap,  it  is  as  much 
as  could  be  expected  of  this  evidence. 

•  The  prodigious  extent  of  denudation  which  has  been  already  demon- 
strated to  have  occurred  at  former  periods,  will  reconcile  the  student  to 
the  belief  that  crystalline  rocks  of  high  antiquity,  although  deep  in  the 
earth's  crust  when  originally  formed,  may  have  become  uncovered  and 
exposed  at  the  surface.  Their  actual  elevation  above  the  sea  may  be  re- 
ferred to  the  same  causes  to  which  we  have  attributed  the  upheaval  of 
marine  strata,  even  to  the  summits  of  some  mountain  chains.  But  to 
these  and  other  topics,  I  shall  revert  when  speaking,  in  the  next  chapter, 
of  the  relative  ages  of  different  masses  of  granite. 


CH.  XXXIV.]       TESTS   OF  AGE   OF  PLUTONIC   ROCKS. 
CHAPTER  XXXIV. 

ON   THE  DIFFERENT   AGES   OF  THE   PLUTONIC  ROCKS. 

Difficulty  in  ascertaining  the  precise  age  of  a  plutonic  rock  —  Test  of  age  by 
relative  position — Test  by  intrusion  and  alteration — Test  by  mineral  composi- 
tion— Test  by  included  fragments  —  Recent  and  Pliocene  ply  tonic  rocks,  why 
invisible — Tertiary  plutonic  rocks  in  the  Andes — Granite  altering  Cretaceous 
rocks  —  Granite  altering  Lias  in  the  Alps  and  in  Skye —  Granite  of  Dartmoor 
altering  Carboniferous  strata  —  Granite  of  the  Old  Red  Sandstone  period  — 
Syenite  altering  Silurian  strata  in  Norway — Blending  of  the  same  with  gneiss 
—  Most  ancient  plutonic  rocks  —  Granite  protruded  in  a  solid  form  —  On  the 
probable  age  of  the  granites  of  Arran,  in  Scotland. 

WHEN  we  adopt  the  igneous  theory  of  granite,  as  explained  in  the 
last  chapter,  and  believe  that  different  plutonic  rocks  have  originated  at 
successive  periods  beneath  the  surface  of  the  planet,  we  must  be  pre- 
pared to  encounter  greater  difficulty  in  ascertaining  the  precise  age  of 
such  rocks,  than  in  the  case  of  volcanic  and  fossiliferous  formations. 
We  must  bear  in  mind,  that  the  .evidence  of  the  age  of  each  contempo- 
raneous volcanic  rock  was  derived,  either  from  lavas  poured  out  upon  the 
ancient  surface,  whether  in  the  sea  or  in  the  atmosphere,  or  from  tuffs 
and  conglomerates,  also  deposited  at  the  surface,  and  either  containing 
organic  remains  themselves,  or  intercalated  between  strata  containing 
fossils.  But  all  these  tests  fail  when  we  endeavour  to  fix  the  chrono- 
logy of  a  rock  which  has  crystallized  from  a  state  of  fusion  in  the  bowels 
of  the  earth.  In  that  case,  we  are  reduced  to  the  following  tests ;  1st, 
relative  .position ;  2dly,  intrusion,  and  alteration  of  the  rocks  in  contact ; 
3dly,  mineral  characters ;  4thly,  included  fragments. 

Test  of  age  by  relative  position.  —  Unaltered  fossiliferous  strata  of 
every  age  are  met  with  reposing  immediately  on  plutonic  rocks ;  as  at 
Christiania,  in  Norway,  where  the  Newer  Pliocene  deposits  rest  on  gra- 
nite ;  in  Auvergne,  where  the  fresh-water  Eocene  strata,  and  at  Heidel- 
berg, on  the  Rhine,  where  the  New  Red  sandstone,  occupy  a  similar 
place.  In  all  these,  and  similar  instances,  inferiority  in  position  is  con- 
nected with  the  superior  antiquity  of  granite.  The  crystalline  rock  was 
solid  before  the  sedimentary  beds  were  superimposed,  and  the  latter 
usually  contain  in  them  rounded  pebbles  of  the  subjacent  granite. 

Test  by  intrusion  and  alteration.  —  But  when  plutonic  rocks  send 
veins  into  strata,  and  alter  them  near  the  point  of  contact,  in  the  manner 
before  described  (p.  567),  it  is  clear  that,  like  intrusive  traps,  they  are 
newer  than  the  strata  which  they  invade  and  alter.  Examples  of  the 
application  of  this  test  will  be  given  in  the  sequel. 

Test  by  mineral  composition. — Notwithstanding  a  general  uniformity 
in  the  aspect  of  plutonic  rocks,  we  have  seen  in  the  last  chapter  that 


57,1:  RECENT  AND   PLIOCENE  [Cn.  XXXIV. 

there  are  many  varieties,  such  as  Syenite,  Talcose  granite,  and  others 
One  of  these  varieties  is  sometimes  found  exclusively  prevailing  through- 
out an  extensive  region,  where  it  preserves  a  homogeneous  character ;  so 
that  having  ascertained  its  relative  age  in  one  place,  we  can  easily  recog- 
nize its  identity  in  others,  and  thus  determine  from  a  single  section  the 
chronological  relations  of  large  mountain  masses.  Having  observed,  for 
example,  that  the  syenitic  granite  of  Norway,  in  which  the  mineral 
called  zircon  abounds,  has  altered  the  Silurian  strata  wherever  it  is  in 
contact,  we  do  not  hesitate  to  refer  other  masses  of  the  same  zircon- 
syenite  in  the  south  of  Norway  to  the  same  era. 

Some  have  imagined  that  the  age  of  different  granites  might,  to  a 
great  extent,  be  determined  by  their  mineral  characters  alone ;  syenite, 
for  instance,  or  granite  with  hornblende,  being  more  modern  xhan  com- 
mon or  micaceous  granite.  But  modern  investigations  have  proved  these 
generalizations  to  have  been  premature.  The  syenitic  granite  of  Nor- 
way  already  alluded  to  may  be  of  the  same  age  as  the  Silurian  strata, 
which  it  traverses  and  alters,  or  may  belong  to  the  Old  Red  sandstone 
period ;  whereas  the  granite  of  Dartmoor,  although  consisting  of  mica, 
quartz,  and  felspar,  is  newer  than  the  coal.  (See  p.  580.) 

Test  ~by  included  fragments.  —  This  criterion  can  rarely  be  of  much 
importance,  because  the  fragments  involved  in  granite  are  usually  so 
much  altered,  that  they  cannot  be  referred  with  certainty  to  the  rocks 
whence  they  were  derived.  In  the  White  Mountains,  in  North  Ame- 
rica, according  to  Professor  Hubbard,  a  granite  vein  traversing  granite, 
contains  fragments  of  slate  and  trap,  which  must  have  fallen  into  the 
fissure  when  the  fused  materials  of  the  vein  were  injected  from  below,* 
and  thus  the  granite  is  shown  to  be  newer  than  certain  superficial  slaty 
and  trappean  formations. 

Recent  and  Pliocene  plutonic  rocks,  why  invisible. — The  explanation 
already  given  in  the  29th  and  in  the  last  chapter,  of  the  probtfble  rela- 
tion of  the  plutonic  to  the  volcanic  formations,  will  naturally  lead  the 
reader  to  infer,  that  rocks  of  the  one  class  can  never  be  produced  at 
or  near  the  surface  without  some  members  of  the  other  being  formed 
below  simultaneously,  or  soon  afterwards.  It  is  not  uncommon  for  lava- 
streams  to  require  more  than  ten  years  to  cool  in  the  open  air ;  and 
where  they  are  of  great  depth  a  much  longer  period.  The  melted 
matter  poured  from  Jorullo,  in  Mexico,  in  the  year  1759,  which  accu- 
mulated in  some  places  to  the  height  of  550  feet,  was  found  to  retain  a 
high  temperature  half  a  century  after  the  eruption. f  "VVe  may  conceive, 
therefore,  that  great  masses  of  subterranean  lava  may  remain  in  a  red- 
hot  or  incandescent  state  in  the  volcanic  foci  for  immense  periods,  and 
the  process  of  refrigeration  may  be  extremely  gradual.  Sometimes,  in- 
deed, this  process  may  be  retarded  for  an  indefinite  period,  by  the  acces- 
sion of  fresh  supplies  of  heat ;  for  we  find  that  the  lava  in  the  crater  of 
Stromboli,  one  of  the  Lipari  Islands,  has  been  in  a  state  of  constant 

*  Silliman's  Journ.,  No.  69,  p.  123.      f  See  "  Principles,"  Index,  "  Jorullo." 


CH.  XXXIV.]  PLUTONIC   ROCKS.  575 

ebullition  for  the  last  two  thousand  years ;  and  we  may  suppose  this 
fluid  mass  to  communicate  with  some  caldron  or  reservoir  of  fused 
matter  below.  In  the  Isle  of  Bourbon,  also,  where  there  has  been  an 
emission  of  lava  once  in  every  two  years  for  a  long  period,  the  lava 
below  can  scarcely  fail  to  have  been  permanently  in  a  state  of  liquefac- 
tion. If  then  it  be  a  reasonable  conjecture,  that  about  2000  volcanic 
eruptions  occur  in  the  course  of  every  century,  either  above  the  waters 
of  the  sea  or  beneath  them,*  it  will  follow  that  the  quantity  of  plutonic 
rock  generated,  or  in  progress  during  the  Recent  epoch,  must  already 
have  been  considerable. 

But  as  the  plutonic  rocks  originate  at  some  depth  in  the  earth's  crust, 
they  can  only  be  rendered  accessible  to  human  observation  by  subsequent 
upheaval  and  denudation.  Between  the  period  when  a  plutonic  rock 
crystallizes  in  the  subterranean  regions,  and  the  era  of  its  protrusion  at 
any  single  point  of  the  surface,  one  or  two  geological  periods  must 
usually  intervene.  Hence,  we  must  not  expect  to  find  the  Recent  or 
Newer  Pliocene  granites  laid  open  to  view,  unless  we  are  prepared  to 
assume  that  sufficient  time  has  elapsed  since  the  commencement  of  the 
Newer  Pliocene  period  for  great  upheaval  and  denudation.  A  plutonic 
rock,  therefore,  must,  in  general,  be  of  considerable  antiquity  relatively 
to  the  fossiliferous  and  volcanic  formations,  before  it  becomes  extensively 
visible.  As  we  know  that  the  upheaval  of  land  has  been  sometimes 
accompanied  in  South  America  by  volcanic  eruptions  and  the  emission 
of  lava,  we  may  conceive  the  more  ancient  plutonic  rocks  to  be  forced 
upwards  to  the  surface  by  the  newer  rocks  of  the  same  class  formed  suc- 
cessively below, — subterposition  in  the  plutonic,  like  superposition  in  the 
sedimentary  rocks,  being  usually  characteristic  of  a  newer  origin. 

In  the  accompanying  diagram  (fig.  697),  an  attempt  is  made  to  show 
the  inverted  order  in  which  sedimentary  and  plutonic  formations  may 
occur  in  the  earth's  crust. 

The  oldest  plutonic  rock,  No.  I.,  has  been  upheaved  at  successive 
periods  until  it  has  become  exposed  to  view  in  a  mountain-chain.  This 
protrusion  of  No.  I.  has  been  caused  by  the  igneous  agency  which  pro- 
duced the  newer  plutonic  rocks  Nos.  II.,  III.,  and  IV.  Part  of  the 
primary  fossiliferous  strata,  No.  1,  have  also  been  raised  to  the  surface 
by  the  same  gradual  process.  It  will  be  observed  that  the  Recent 
strata  No.  4,  and  the  Recent  granite  or  plutonic  rock  No.  IV.,  are  the 
most  remote  from  each  other  in  position,  although  of  contemporaneous 
date.  According  to  this  hypothesis,  the  convulsions  of  many  periods 
will  be  required  before  Recent  granite,  or  granite  of  the  human  period, 
will  be  upraised  so  as  to  form  the  highest  ridges  and  central  axes  of 
mountain-chains.  During  that  time  the  Recent  strata  No.  4  might  be 
covered  by  a  great  many  newer  sedimentary  formations. 

Eocene  granite  and  plutonic  rocks. — In  a  former  part  of  this  volume 
(p.  230),  the  great  nummulitic  formation  of  the  Alps  and  Pyrenees  was 

*  "  Principles,"  Index,  "  Volcanic  Eruptions." 


576 


PLUTONIC   ROCKS. 


[CH.  XXXIV, 


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CH.  XXXIV.]    PLUTONIC  BOCKS  OF  THE  ANDES.          577 

referred  to  the  Eocene  period,  and  it  follows  that  those  vast  movements 
which  have  raised  fossiliferous  rocks  from  the  level  of  the  sea  to  the 
height  of  more  than  10,000  feet  above  its  level  have  taken  place  since 
the  commencement  of  the  tertiary  epoch.  Here,  therefore,  if  anywhere, 
we  might  expect  to  find  hypogene  formations  of  Eocene  date  breaking 
out  in  the  central  axis  or  most  disturbed  region  of  the  loftiest  chain  in 
Europe.  Accordingly,  in  the  Swiss  Alps,  even  theflysch,  or  upper  por- 
tion of  the  nummulitic  series,  has  been  occasionally  invaded  by  plutonic 
rocks,  and  converted  into  crystalline  schists-  of  the  hypogene  class. 
There  can  be  little  doubt  that  even  the  talcose  granite  or  gneiss  of  Mont 
Blanc  itself  has  been  in  a  fused  or  pasty  state  since  the  flysch  was  de- 
posited at  the  bottom  of  the  sea ;  and  the  question  as  to  its  age  is  not  so 
much  whether  it  be  a  secondary  or  tertiary  granite,  or  gneiss,  as  whether 
it  should  be  assigned  to  the  Eocene  or  Miocene  epoch. 

Great  upheaving  movements  have  been  experienced  in  the  region  of 
the  Andes,  during  the  Post-Pliocene  period.  In  some  part,  therefore, 
of  this  chain,  we  may  expect  to  discover  tertiary  plutonic  rocks  laid  open 
to  view.  What  we  already  know  of  the  structure  of  the  Chilian  Andes 
seems  to  realize  this  expectation.  In  a  transverse  section,  examined  by 
Mr.  Darwin,  between  Valparaiso  and  Mendoza,  the  Cordillera  was  found 
to  consist  of  two  separate  and  parallel  chains,  formed  of  sedimentary 
rocks  of  different  ages,  the  strata  in  both  resting  on  plutonic  rocks,  by 
which  they  have  been  altered.  In  the  western  or  oldest  range,  called 
the  Peuquenes,  are  black  calcareous  clay-slates,  rising  to  the  height  of 
nearly  14,000  feet  above  the  sea,  in  which  are  shells  of  the  genera  Gry- 
phaea,  Turritetta,  Terebratula,  and  Ammonite.  These  rocks  are  sup- 
posed to  be  of  the  age  of  the  central  parts  of  the  secondary  series  of 
Europe.  They  are  penetrated  and  altered  by  dikes  and  mountain  masses 
of  a  plutonic  rock,  which  has  the  texture  of  ordinary  granite,  but  rarely 
contains  quartz,  being  a  compound  of  albite  and  hornblende. 

The  second  or  eastern  chain  consists  chiefly  of  sandstones  and  con- 
glomerates, of  vast  thickness,  the  materials  of  which  are  derived  from 
the  ruins  of  the  western  chain.  The  pebbles  of  the  conglomerates  are, 
for  the  most  part,  rounded  fragments  of  the  fossiliferous  slates  before 
mentioned.  The  resemblance  of  the  whole  series  to  certain  tertiary 
deposits  on  the  shores  of  the  Pacific,  not  only  in  mineral  character,  but 
in  the  imbedded  lignite  and  silicified  woods,  leads  to  the  conjecture  that 
they  also  are  tertiary.  Yet  these  strata  are  not  only  associated  with  trap 
rocks  and  volcanic  tuffs,  but  are  also  altered  by  a  granite  consisting  of 
quartz,  felspar,  and  talc.  They  are  traversed,  moreover,  by  dikes  of  the 
same  granite,  and  by  numerous  veins  of  iron,  copper,  arsenic,  silver,  and 
gold ;  all  of  which  can  be  traced  to  the  underlying  granite.*  "We  have, 
therefore,  strong  ground  to  presume  that  the  plutonic  rock,  here  exposed 
on  a  large  scale  in  the  Chilian  Andes,  is  of  later  date  than  certain  terti- 
ary formations. 

«  Darwin,  pp.  390,  406;  second  edition,  p.  319. 
37 


578  VOLUME   OP  HIDDEN   PLUTONIC   ROCKS.      [On.  XXXIV. 

But  the  theory  adopted  in  this  work  of  the  subterranean  origin  of  the 
hypogene  formations  would  be  untenable,  if  the  supposed  fact  here 
alluded  to,  of  the  appearance  of  tertiary  granite  at  the  surface  was  not 
a  rare  exception  to  the  general  rule.  A  considerable  lapse  of  time  must 
intervene  between  the  formation,  in  the  nether  regions,  of  plutonic  and 
metamorphic  rocks,  and  their  emergence  at  the  surface.  For  a  long 
series  of  subterranean  movements  must  occur  before  such  rocks  can  be 
uplifted  into  the  atmosphere  or  the  ocean ;  and,  before  they  can  be  ren- 
dered visible  to  man,  some  strata  which  previously  covered  them  must 
usually  have  been  stripped  off  by  denudation. 

We  know  that  in  the  Bay  of  Baiae,  in  1538,  in  Cutch  in  1819,  and 
on  several  occasions  in  Peru  and  Chili,  since  the  commencement  of  the 
present  century,  the  permanent  upheaval  or  subsidence  of  land  has  been 
accompanied  by  the  simultaneous  emission  of  lava  at  one  or  more  points 
in  the  same  volcanic  region.  From,  these  and  other  examples  it  may  be 
inferred  that  the  rising  or  sinking  of  the  earth's  crust,  operations  by 
which  sea  is  converted  into  land,  and  land  into  sea,  are  a  part  only  of 
the  consequences  of  subterranean  igneous  action.  It  can  scarcely  be 
doubted  that  this  action  consists,  in  a  great  degree,  of  the  baking,  and 
occasionally  the  liquefaction,  of  rocks,  causing  them  to  assume,  in  some 
cases  a  larger,  in  other  a  smaller  volume  than  before  the  application  of 
heat.  It  consists  also  in  the  generation  of  gases,  and  their  expansion 
by  heat,  and  the  injection  of  liquid  matter  into  rents  formed  in 
superincumbent  rocks.  The  prodigious  scale  on  which  these  subterranean 
causes  have  operated  in  Sicily  since  the  deposition  of  the  Newer 
Pliocene  strata  will  be  appreciated,  when  we  remember  that  throughout 
half  the  surface  of  that  island  such  strata  are  met  with,  raised  to  the 
height  of  from  50  to  that  of  2000  and  even  3000  feet  above  the  level 
of  the  sea.  In  the  same  island  also  the  older  rocks  which  are  contiguous 
to  these  marine  tertiary  strata  must  have  undergone,  within  the  same 
period,  a  similar  amount  of  upheaval. 

The  like  observations  may  be  extended  to  nearly  the  whole  of  Europe, 
for,  since  the  commencement  of  the  Eocene  period,  the  entire  European 
area,  including  some  of  the  central  and  very  lofty  portions  of  the  Alps 
themselves,  as  I  have  elsewhere  shown*,  has,  with  the  exception  of  a 
few  districts,  emerged  from  the  deep  to  its  present  altitude ;  and  even 
those  tracts,  which  were  already  dry  land  before  the  Eocene  era,  have 
almost  everywhere  acquired  additional  height.  A  large  amount  of 
subsidence  has  also  occurred  during  the  same  period,  so  that  the 
extent  of  the  subterranean  spaces  which  have  either  become  the 
receptacles  of  sunken  fragments  of  the  earth's  crust,  or  have  been  ren- 
dered capable  of  supporting  other  fragments  at  a  much  greater  height 
than  before,  must  be  so  great  that  they  probably  equal,  if  not  exceed  in 
volume,  the  entire  continent  of  Europe.  We  are  entitled,  therefore,  to 
ask  what  amount  of  change  of  equivalent  importance  can  be  proved  to 

*  See  map  of  Europe  and  explanation,  in  Principles,  book  L 


CH.  XXXIV.]      PLUTONIC   ROCKS   OF   OOLITE  AND   LIAS.  570 

have  occurred  in  the  earth's  crust  within  an  equal  quantity  of  time  an- 
terior to  the  Eocene  epoch.  They  who  contend  for  the  more  intense 
energy  of  subterranean  causes  in  the  remoter  eras  of  the  earth's  history, 
may  find  it  more  difficult  to  give  an  answer  to  this  question  than  they 
anticipated. 

The  principal  effect  of  volcanic  action  in  the  nether  regions,  during 
the  tertiary  period,  seems  to  have  consisted  in  the  upheaval  to  the  sur- 
face of  hypogene  formations  of  an  age  anterior  to  the  carboniferous. 
The  repetition  of  another  series  of  movements,  of  equal  violence,  might 
upraise  the  plutonic  and  metamorphic  rocks  of  many  secondary  periods ; 
and  if  the  same  force  should  still  continue  to  act,  the  next  convulsions 
might  bring  up  to  the  day,  the  tertiary  and  recent  hypogene  rocks.  In 
the  course  of  such  changes  many  of  the  existing  sedimentary  strata 
would  suffer  greatly  by  denudation,  others  might  assume  a  meta- 
morphic structure,  or  become  melted  down  into  plutonic  and  volcanic 
rocks.  Meanwhile  the  deposition  of  a  vast  thickness  of  new  strata  would 
not  fail  to  take  place  during  the  upheaval  and  partial  destruction  of  the 
older  rocks.  But  I  must  refer  the  reader  to  the  last  chapter  but  one  of 
this  volume  for  a  fuller  explanation  of  these  views. 

Cretaceous  period.  —  It  will  be  shown  in  the  next  chapter  that  chalk, 
as  well  as  lias,  has  been  altered  by  granite  in  the  eastern  Pyrenees. 
Whether  such  granite  be  cretaceous  or  tertiary  cannot  easily  be  decided. 
Pig.  69S.  Suppose  b,  GJ  d,  to  be  three  members  of 

the  Cretaceous  series,  the  lowest  of  which, 
b,  has  been  altered  by  the  granite  A,  the 
modifying  influence  not  having  extended 
so  far  as  c,  or  having  but  slightly  affected 
its  lowest  beds.  Now  it  can  rarely  be 
possible  for  the  geologist  to  decide  whether 
the  beds  d  existed  at  the  time  of  the  intrusion  of  A,  and  alteration  of 
b  and  c,  or  whether  they  were  subsequently  thrown  down  upon  c. 

But  as  some  cretaceous  and  even  tertiary  rocks  have  been  raised  to 
the  height  of  more  than  9000  feet  in  the  Pyrenees,  we  must  not  assume 
that  plutonic  formations  of  the  same  periods  may  not  have  been  brought 
up  and  exposed  by  denudation,  at  the  height  of  2000  or  3000  feet  on 
the  flanks  of  that  chain. 

Period  of  Oolite  and  Lias. — In  the  department  of  the  Hautes  Alpes, 
in  France,  near  Vizille,  M.  Elie  de  Beaumont  traced  a  black  argillaceous 
limestone,  charged  with  belemnites,  to  within  a  few  yards  of  a  mass  of 
granite.  Here  the  limestone  begins  to  put  on  a  granular  texture,  but 
is  extremely  fine-grained.  When  nearer  the  junction  it  becomes  gray, 
and  has  a  saccharoid  structure.  In  another  locality,  near  Champoleon,  a 
granite  composed  of  quartz,  black  mica,  and  rose-colored  felspar,  is 
observed  partly  to  overlie  the  secondary  rocks,  producing  an  alteration 
which  extends  for  about  30  feet  downwards,  diminishing  in  the  beds 
which  lie  farthest  from  the  granite.  (See  fig.  699.)  In  the  altered 


580 


PLUTONIC   ROCKS   OF   THE 


[Cn.  XXXIT. 


J  unction  of  granite  with  Jurassic  or  Oolite  strata  in 
the  Alps,  near  Champoleon. 


mass  the  argillaceous  beds  are 
hardened,  the  limestone  is  sac- 
charoid;  the  gritz  quartzose, 
and  in  the  midst  of  them  is  a 
thin  layer  of  an  imperfect 
granite.  It  is  also  an  impor- 
tant circumstance  that  near 
the  point  of  contact,  both  the 
granite  and  the  secondary 
rocks  become  metalliferous, 
and  contain  nests  and  small 
veins  of  blende,  galena,  iron, 
and  copper  pyrites.  The  stra- 
tified rocks  become  harder  and 
more  crystalline,  but  the  gra- 
nite, on  the  contrary,  softer 
and  less  perfectly  crystallized 
near  the  junction.* 

Although  the  granite  is  incumbent  in  the  above  section  (fig.  699),  we 
cannot  assume  that  it  overflowed  the  strata,  for  the  disturbances  of  the 
rocks  are  so  great  in  this  part  of  the  Alps  that  they  seldom  retain  the 
position  which  they  must  originally  have  occupied. 

A  considerable  mass  of  syenite,  in  the  Isle  of  Skye,  is  described  by 
Dr.  MacCulloch  as  intersecting  limestone  and  shale,  which  are  of  the 
age  of  the  lias."f"  The  limestone,  which,  at  a  greater  distance  from  the 
granite,  contains  shells,  exhibits  no  traces  of  them  near  its  junction, 
where  it  has  been  converted  into  a  pure  crystalline  marble. J 

At  Predazzo,  in  the  Tyrol,  secondary  strata,  some  of  which  are  lime- 
stones of  the  Oolite  period,  have  been  traversed  and  altered  by  plutonic 
rocks,  one  portion  of  which  is  an  augitic  porphyry,  which  passes  insen- 
sibly into  granite.  The  limestone  is  changed  into  granular  marble,  with 
a  band  of  serpentine  at  the  j unction. § 

Carboniferous  period.  — The  granite  of  Dartmoor,  in  Devonshire,  was 
formerly  supposed  to  be  one  of  the  most  ancient  of  the  plutonic  rocks, 
but  is  now  ascertained  to  be  posterior  in  date  to  the  culm-measures  of 
that  county,  which,  from  their  position,  and  as  containing  true  coal- 
plants,  are  regarded  by  Professor  Sedgwick  and^Sir  K.  Murchison  as 
members  of  the  true  carboniferous  series.  This  granite,  like  the  syeni- 
tic  granite  of  Christiania,  has  broken  through  the  stratified  formations 
without  much  changing  their  strike.  Hence,  on  the  north-west  side  of 
Dartmoor,  the  successive  members  of  the  culm-measures  abut  against  the 
granite,  and  become  metamorphic  as  they  approach.  These  strata  are 

*  Elie  de  Beaumont,  sur  les  Montagnes  de  1'Oisans,  &c.  M6m.  de  la  Soc. 
1'Hist.  Nat.  de  Paris,  torn.  v. 

f  See  Murchison,  Geol.  Trans.,  2d  series,  vol.  ii.,  part  ii.,  pp.  311 — 321. 
J  Western  Islands,  vol.  i.  p.  330,  plate  18,  figs.  3,  4. 
§  Von  Buch,  Annales  de  Chimie,  &c. 


CH.  XXXIV.]        CARBONIFEROUS   AND   SILURIAN   PERIODS. 


581 


also  penetrated  by  granite  veins,  and  plutonic  dikes,  called  "  el  vans."* 
The  granite  of  Cornwall  is  probably  of  the  same  date,  and,  therefore, 
as  modern  as  the  Carboniferous  strata,  if  not  much  newer. 

Silurian  period.  —  It  has  long  been  known  that  the  granite  neai 
Christiania,  in  Norway,  is  of  newer  origin  than  the  Silurian  strata  of 
that  region.  Von  Buch  first  announced,  in  1813,  the  discovery  of  its 
posteriority  in  date  to  limestones  containing  orthocerata  and  trilobites. 
The  proofs  consist  in  the  penetration  of  granite  veins  into  the  shale 
and  limestone,  and  the  alteration  of  the  strata,  for  a  considerable  dis- 
tance from  the  point  of  contact,  both  of  these  veins  and  the  central  mass 
from  which  they  emanate.  (See  p.  572.)  Von  Buch  supposed  that  the 
plutonic  rock  alternated  with  the  fossiliferous  strata,  and  that  large 
masses  of  granite  *?ere  sometimes  incumbent  upon  the  strata ;  but  this 
idea  was  erroneous,  and  arose  from  the  fact  that  the  beds  of  shale  and 
limestone  often  dip  towards  the  granite  up  to  the  point  of  contact,  ap- 
pearing as  if  they  would  pass  under  it  in  mass,  as  .it  a,  fig.  700,  and 
then  again  on  the  opposite  side  of  the  same  mountain,  as  at  b,  dip  away 
from  the  same  granite.  When  the  junctions,  however,  are  carefully 
examined,  it  is  found  that  the  plutonic  rock  intrudes  itself  in  veins,  and 
nowhere  covers  the  fossiliferous  strata  in  large  overlying  masses,  as  is 
so  commonly  the  case  with  trappean  formations.f 

Fig.  700. 


Silurian. 


Granite. 


Silurian  Strata. 


Now  this  granite,  which  is  more  modern%than  the  Silurian  strata  of 
Norway,  also  sends  veins  in  the  same  country  into  an  ancient  formation 
of  gneiss  ;  and  the  relations  of  the  plutonic  rock  and  the  gneiss  at  their 
junction,  are  full  of  interest  when  we  duly  consider  the  wide  difference  of 
epoch  which  must  have  separated  their  origin. 

The  length  of  this  interval  of  time  is  attested  by  the  following  facts : — 
The  fossiliferous,  or  Silurian  beds,  rest  unconformably  upon  the  trun- 
cated edges  of  the  gneiss,  the  inclined  strata  of  which  had  been 
denuded  before  the  sedimentary  beds  were  superimposed  (see  fig. 
701).  The  signs  of  denudation  are  twofold;  first,  the  surface  of  the 


Fig.  701. 


Gneiss.    .  Granite.  Gneiss. 

Granite  sending  veins  into  Silurian  strata  and  Gneiss,— Christiania,  Norway. 

*  Proceed.  Geol.  Soc.  voL  il  p.  562,  and  Trans.  2d  ser.  vol.  v.  p.  686. 
f  See  the  Gaea  Norvegica  and  other  works  of  Keilhau,  with  whom  I  examined 
this  country. 


582  PROTRUSION   OF  SOLID   GRANITE.         [On.  XXXIY. 

gneiss  is  seen  occasionally,  on  the  removal  of  the  newer  beds,  containing 
organic  remains,  to  be  worn  and  smoothed ;  secondly,  pebbles  of  gneiss 
have  been  fou-nd  in  some  of  the  Silurian  strata.  Between  the  origin, 
therefore,  of  the  gneiss  and  the  granite  there  intervened,  first,  the  period 
when  the  strata  of  gneiss  were  denuded  ;  2dly,  the  period  of  the  deposition 
of  the  Silurian  deposits.  Yet  the  granite  produced,  after  this  long  interval, 
is  often  so  intimately  blended  with  the  ancient  gneiss,  at  the  point  of 
junction,  that  it  is  impossible  to  draw  any  other  than  an  arbitrary  line 
of  separation  between  them ;  and  where  this  is  not  the  case,  tortuous 
veins  of  granite  pass  freely  through  gneiss,  ending  sometimes  in  threads, 
as  if  the  older  rock  had  offered  no  resistance  to  their  passage.  It  seems 
necessary,  therefore,  to  conceive  that  the  gneiss  was  softened  and  more 
or  less  melted  when  penetrated  by  the  granite.  But  tad  such  junctions 
alone  been  visible,  and  had  we  not  learnt,  from  other  sections,  how  long 
a  period  elapsed  between  the  consolidation  of  the  gneiss  and  the  injec- 
tion of  this  granite,  we  might  have  suspected  that  the  gneiss  was  scarcely 
solidified,  or  had  not  yet  assumed  its  complete  metamorphic  character, 
when  invaded  by  the  plutonic  rock.  From  this  example  we  may  learn 
how  impossible  it  is  to  conjecture  whether  certain  granites  in  Scotland, 
and  other  countries,  which  send  veins  into  gneiss  and  other  metamorphic 
rocks,  are  primary,  or  whether  they  may  not  belong  to  some  secondary 
or  tertiary  period. 

Oldest  granites. — It  is  not  half  a  century  since  the  doctrine  was  very 
general  that  all  granitic  rocks  were  primitive,  that  is  to  say,  that  they 
originated  before  the  deposition  of  the  first  sedimentary  strata,  and 
before  the  creation  of  organic  beings  (see  above,  p.  9).  But  so  greatly 
are  our  views  now  changed,  that  we  find  it  no  easy  task  to  point  out  a 
single  mass  of  granite  demonstrably  more  ancient  than  all  the  known 
fossiliferous  deposits.  Could  we  discover  some  Lower  Cambrian  strata 
resting  immediately  on  granite,  there  being  no  alterations  at  the  point 
of  contact,  nor  any  intersecting  granitic  veins,  we  might  then  affirm  the 
plutonic  rock  to  have  originated  before  the  oldest  known  fossiliferous 
strata.  Still  it  would  be  presumptuous,  as  we  have  already  pointed  out, 
p.  452,  to  suppose  that  when  a  small  part  only  of  the  globe  has  been 
investigated,  we  are  acquainted  with  the  oldest  fossiliferous  strata  in  the 
crust  of  our  planet.  Even  when  these  are  found,  we  cannot  assume  that 
there  never  were  any  antecedent  strata  containing  organic  remains,  which 
may  have  become  metamorphic.  If  we  find  pebbles  of  granite  in  a  con- 
glomerate of  the  Lower  Cambrian  system,  we  may  then  feel  assured  that 
the  parent  granite  was  formed  before  the  Lower  Cambrian  formation. 
But  if  the  incumbent  strata  be  merely  Silurian  or  Upper  Cambrian,  the 
fundamental  granite,  although  of  high  antiquity,  may  be  posterior  in  date 
to  known  fossiliferous  formations. 

Protrusion  of  solid  granite. — In  part  of  Sutherlandshire,  near  Brora, 
common  granite,  composed  of  felspar,  quartz,  and  mica,  is  in  immediate 
contact  with  Oolitic  strata,  and  has  clearly  been  elevated  to  the  surface 


CH.  XXXIV.]  AGE   OF   GRANITES   OF   ARRAN.  583 

at  a  period  subsequent  to  the  deposition  of  those  strata.*  Professor 
Sedgwick  and  Sir  R.  Murchison  conceive  that  this  granite  has  been  up- 
heaved in  a  solid  form ;  and  that  in  breaking  through  the  submarine 
deposits,  with  which  it  was  not  perhaps  originally  in  contact,  it  has  frac- 
tured them  so  as  to  form  a  breccia  along  the  line  of  junction.  This 
breccia  consists  of  fragments  of  shale,  sandstone,  and  limestone,  with 
fossils  of  the  oolite,  all  united  together  by  a  calcareous  cement.  The 
secondary  strata,  at  some  distance  from  the  granite,  are  but  slightly  dis- 
turbed, but  in  proportion  to  their  proximity  the  amount  of  dislocation 
becomes  greater. 

If  we  admit  that  solid  hypogene  rocks,  whether  stratified  or  unstrati- 
fied,  have  in  such  cases  been  driven  upwards  so  as  to  pierce  through 
yielding  sedimentary  deposits,  we  shall  be  enabled  to  account  for  many 
geological  appearances  otherwise  inexplicable.  Thus,  for  example,  at 
Weinbohla  and  Hohnstein,  near  Meissen,  in  Saxony,  a  mass  of  granite 
has  been  observed  covering  strata  of  the  Cretaceous  and  Oolitic  periods 
for  the  space  of  between  300  and  400  yards  square.  It  appears  clearly 
from  a  Memoir  of  Dr.  B.  Cotta  on  this  subject,!  that  the  granite  was 
thrust  into  its  actual  position  when  solid.  There  are  no  intersecting  veins 
at  the  junction — no  alteration  as  if  by  heat,  but  evident  signs  of  rubbing, 
and  a  breccia  in  some  places,  in  which  pieces  of  granite  are  mingled  with 
broken  fragments  of  the  secondary  rocks.  As  the  granite  overhangs  both 
the  lias  and  chalk,  so  the  lias  is  in  some  places  bent  over  strata  of  the 
cretaceous  era. 

Relative  age  of  the  granites  of  Arran. — In  this  island,  the  largest  in 
the  Firth  of  Clyde,  being  twenty  miles  in  length  from  north  to  south, 
the  four  great  classes  of  rocks,  the  fossiliferous,  volcanic,  plutonic,  and 
metamorphic,  are  all  conspicuously  displayed  within  a  very  small  area, 
and  with  their  peculiar  characters  strongly  contrasted.  In  the  north 
of  the  island  the  granite  rises  to  the  height  of  nearly  3000  feet  above 
the  sea,  terminating  in  mountainous  peaks.  (See  section,  fig.  702.) 
On  the  flanks  of  the  same  mountains  are  chloritic  schists,  blue  roofing- 
slate,  and  other  rocks  of  the  metamorphic  order  (No.  1),  into  which  the 
granite  (No.  2)  sends  veins.  This  granite,  therefore,  is  newer  than  the 
hypogene  schists  (No.  1),  which  it  penetrates. 

These  schists  are  highly  inclined.  Upon  them  rest  beds  of  conglom- 
erate and  sandstone  (No.  3),  which  are  referable  to  the  Old  Red  forma- 
tion, to  which  succeed  various  shales  and  limestones  (No.  4)  containing 
the  fossils  of  the  Carboniferous  period,  upon  which  are  other  strata  of 
sandstone  and  conglomerate  (upper  part  of  No.  4),  in  which  no  fossils 
have  been  met  with,  which  it  is  conjectured  may  belong  to  the  New  Red 
sandstone  period.  All  the  preceding  formations  are  cut  through  by  the 
volcanic  rocks  (No.  5),  which  consist  of  greenstone,  basalt,  pitchstone, 
claystone-porphyry,  and  other  varieties.  These  appear  either  in  the 

*  Murchison,  Geol.  Trans.,  2d  series,  vol.  ii.  p.  307. 
f  Geognostiche  Wanderungen,  Leipzig,  1838. 


584  AGE   OF  THE  GRANITES.  [On.  XXXIV 

form  of  dikes,  or  in  dense  masses  from  50  to  700  feet  in  thickness 
overlying  the  strata  (No.  4).  They  sometimes  pass  into  syenite  of  so 
crystalline  a  form,  that  it  may  rank  as  a  plutonic  formation ;  and  in  one 
region,  at  Ploverfield,  in  Glen  Cloy,  a  fine-grained  granite  (6  a)  is  seen 
associated  with  the  trap  formation,  and  sending  veins  into  the  sandstone 
or  into  the  upper  strata  of  No.  4.  This  interesting  discovery  of  granite 
in  the  southern  region  of  Arran,  at  a  point  where  it  is  separated  from 
the  northern  mass  of  granite  by  a  great  thickness  of  secondaiy  strata 
and  overlying  trap,  was  made  by  Mr.  L.  A.  Necker  of  Geneva,  during 
his  survey  of  Arran,  in  1839.  We  also  learn  from  late  investiga- 
tions by  Professor  A.  C.  Ramsay,  that  a  similar  fine-grained  granite  (No. 
6  6)  appears  in  the  interior  of  the  northern  granitic  district,  forming  the 
nucleus  of  it,  and  sending  veins  into  the  older  coarse-grained  granite 
(No.  2).  The  trap  dikes  which  penetrate  the  older  granite  are  cut  off, 
according  to  Mr.  Ramsay,  at  the  junction  of  the  fine-grained. 

It  is  not  improbable  that  the  granite  (No.  6  5)  may  be  of  the  same 
age  as  that  of  Ploverfield  (No.  6  a),  and  this  again  may  belong  to  the 
same  geological  epoch  as  the  trap  formations  (No.  5).  If  there  be  any 
difference  of  date,  it  would  seem  that  the  fine-grained  granite  must  be 
newer  than  the  trappean  rocks.  But,  on  the  other  hand,  the  coarser 
granite  (No.  2)  may  be  the  oldest  rock  in  Arran,  with  the  exception  of 
the  hypogene  slates  (No.  1),  into  which  it  sends  veins. 

An  objection  may  perhaps  at  first  be  started  to  this  conclusion,  de- 
rived from  the  curious  and  striking  fact,  the  importance  of  which  wa^ 
first  emphatically  pointed  out  by  Dr.  MacCulloch,  that  no  pebbles  of 
granite  occur  in  the  conglomerates  of  the  red  sandstone  in  Arran,  though 
these  conglomerates  are  several  hundred  feet  in  thickness,  and  lie  at  the 
foot  of  lofty  granite  mountains,  which  tower  above  them.  As  a  general 
rule,  all  such  aggregates  of  pebbles  and  sand  are  mainly  composed  of 
the  wreck  of  pre-existing  rocks  occurring  in  the  immediate  vicinity. 
The  total  absence  therefore  of  granitic  pebbles  has  justly  been  a  theme 
of  wonder  to  those  geologists  who  have  successively  visited  Arran,  and 
they  have  carefully  searched  there,  as  I  have  done  myself,  to  find  an 
exception,  but  in  vain.  The  rounded  masses  consist  exclusively  of 
quartz,  chlorite-schist,  and  other  members  of  the  metamorphic  series; 
nor  in  the  newer  conglomerates  of  No.  4  have  any  granitic  fragments 
been  discovered.  Are  we  then  entitled  to  affirm  that  the  coarse-grained 
granite  (No.  2),  like  the  fine-grained  variety  (No.  6  a),  is  more  modern 
than  all  the  other  rocks  of  the  island?  This  we  cannot  assume  at 
present,  but  we  may  confidently  infer  that  when  the  various  beds  of 
sandstone  and  conglomerate  were  formed,  no  granite  had  reached  the 
surface,  or  had  been  exposed  to  denudation  in  Arran.  It  is  clear  that 
the  crystalline  schists  were  ground  into  sand  and  shingle  when  the  strata 
No.  3  were  deposited,  and  at  that  time  the  waves  had  never  acted  upon 
the  granite,  which  now  sends  its  veins  into  the  schist.  May  we  then 
conclude,  that  the  schists  suffered  denudation  before  they  were  invaded 
by  granite  ?  This  opinion,  although  not  inadmissible,  is  by  no  meang 


Ctt.  XXXI V.I 


OF   THE    ISLE    OF   ARRAN. 


585 


586  GRANITES   OF  ARRAN.  [Cu.  XXSIV, 

fully  borne  out  by  the  evidence.  For  at  the  time  when  the  Old  Red 
sandstone  originated,  the  metamorphic  strata  may  have  formed  islands 
in  the  sea,  as  in  fig.  703,  over  which  the  breakers  rolled,  or  from  which 


Fig.  703. 
Sea 


torrents  and  rivers  descended,  carrying  down  gravel  and  sand.  The 
plutonic  rock  or  granite  (B)  may  even  then  have  lt«en  previously  in- 
jected at  a  certain  depth  below,  and  yet  may  never  have  been  exposed 
to  denudation. 

As  to  the  time  and  manner  of  the  subsequent  protrusion  of  the  coarse- 
grained granite  (No.  2),  this  rock  may  have  been  thrust  up  bodily,  in  a 
solid  form,  during  that  long  series  of  igneous  operations  which  produced 
the  trappean  and  plutonic  formations  (Nos.  5,  6  a,  and  6  6). 

We  have  shown  that  these  eruptions,  whatever  their  date,  were  poste- 
rior to  the  deposition  of  all  the  fossiliferous  strata  of  Arran.  We  can 
also  prove  that  subsequently  both  the  granitic  and  trappean  rocks  under- 
went great  aqueous  denudation,  which  they  probably  suffered  during 
their  emergence  from  the  sea.  The  fact  is  demonstrated  by  the  abrupt 
truncation  of  numerous  dikes,  such  as  those  at  c,  c?,  e,  which  are  cut  off 
on  the  surface  of  the  granite  and  trap.  The  overlying  trap  also  ceases 
very  abruptly  on  approaching  the  boundary  of  the  great  hypogene 
region,  and  terminates  in  a  steep  escarpment  facing  towards  it  as  at  /, 
fig.  702.  When,  in  its  original  fluid  state  it  could  not  have  come  thus 
suddenly  to  an  end,  but  must  have  filled  up  the  hollow  now  separating  it 
from  the  hypogene  rocks,  had  such  a  hollow  then  existed.  This  neces- 
sity of  supposing  that  both  the  trap  and  the  conglomerate  once  extended 
farther,  and  that  veins  such  as  c,  ^,  fig.  702,  were  once  prolonged  farther 
upwards,  prepares  us  to  believe  that  the  whole  of  the  northern  granite 
may  at  one  time  have  been  covered  by  newer  formations,  under  the 
pressure  of  which,  before  its  protrusion,  it  assumed  its  highly  crystalline 
texture. 

The  theory  of  the  protrusion  in  a  solid  form  of  the  northern  nucleus 
of  granite  is  confirmed  by  the  manner  in  which  the  hypogene  slates 
(No.  1),  and  the  beds  of  conglomerate  (No.  3),  dip  away  from  it  on  all 
sides.  In  some  places  indeed  the  slates  are  inclined  towards  the  granite, 
but  this  exception  might  have  been  looked  for,  because  these  hypogene 
strata  have  undergone  disturbances  at  more  than  one  geological  epoch, 
and  may  at  some  points,  perhaps,  have  their  original  order  of  position 
inverted.  The  high  inclination,  therefore,  and  the  quaquaversal  dip  of 
the  beds  around  the  borders  of  the  granitic  boss,  and  the  comparative 
horizontality  of  the  fossiliferous  strata  in  the  southern  part  of  the  island, 
are  facts  which  all  accord  with  the  hypothesis  of  a  great  amount  of 
movement  at  that  point  where  the  granite  is  supposed  to  have  been 


CH.  XXXV.]  METAMOKPHIC   ROCKS.  587 

thrust  up  bodily,  and  where  we  may  conceive  it  to  have  been  dis- 
tended  laterally  by  the  repeated  injection  of  fresh  supplies  of  melted 
materials.*  - 


CHAPTER  XXXV. 

METAMORPHIC    ROCKS. 

General  character  of  metamorphic  rocks — Gneiss — Hornblende-schist — Mica- 
schist — Clay-slate — Quartzite — Chlorite-schist  —  Metamorphic  limestone — Al- 
phabetical list  and  explanation  of  the  more  abundant  rocks  of  this  family — 
Origin  of  the  metamorphic  strata — Their  stratification — Fossiliferous  strata  near 
intrusive  masses  of  granite  converted  into  rocks  identical  with  different  mem- 
bers of  the  metamorphic  series — Arguments  hence  derived  as  to  the  nature  of 
plutonic  action — Time  may  enable  this  action  to  pervade  denser  masses — From 
what  kinds  of  sedimentary  rock  each  variety  of  the  metamorphic  class  may  be 
derived — Certain  objections  to  the  metamorphic  theory  considered — Partial 
conversion  of  Eocene  slate  into  gneiss. 

WE  have  now  considered  three  distinct  classes  of  rocks :  first,  the 
aqueous,  or  fossiliferous ;  secondly,  the  volcanic ;  and,  thirdly,  the  plu- 
tonic, or  granitic  ;  and  we  have  now,  lastly,  to  examine  those  crystalline 
(or  hypogene)  strata  to  which  the  name  of  metamorphic  has  been  assigned. 
The  last-mentioned  term  expresses,  as  before  explained,  a  theoretical  opin- 
ion that  such  strata,  after  having  been  deposited  from  water,  acquired,  by 
the  influence  of  heat  and  other  causes,  a  highly  crystalline  texture.  They 
who  still  question  this  opinion  may  call  the  rocks  under  consideration  the 
stratified  hypogene,  or  schistose  hypogene  formations. 

These  rocks,  when  in  their  most  characteristic  or  normal  state,  are 
wholly  devoid  of  organic  remains,  and  contain  no  distinct  fragments  of 
other  rocks,  whether  rounded  or  angular.  They  sometimes  break  out  in 
the  central  parts  of  narrow  mountain  chains,  but  in  other  cases  extend 
over  areas  of  vast  dimensions,  occupying,  for  example,  nearly  the  whole  of 
Norway  and  Sweden,  where,  as  in  Brazil,  they  appear  alike  in  the  lower 
and  higher  grounds.  In  Great  Britain,  those  members  of  the  series 
which  approach  most  nearly  to  granite  in  their  composition,  as  gneiss, 
mica-schist,  and  hornblende-schist,  are  confined  to  the  country  north  of 
the  rivers  Forth  and  Clyde. 

However  crystalline  these  rocks  may  become  in  certain  regions,  they 
never,  like  granite  or  trap,  send  veins  into  contiguous"  formations,  whether 
into  an  older  schist  or  granite,  or  into  a  set  of  newer  fossiliferous  strata. 

Many  attempts  have  been  made  to  trace  a  general  order  of  succession 

*  For  the  geology  of  Arran  consult  the  works  of  Drs.  Hutton  and  MacCulloch, 
the  Memoirs  of  Messrs.  Von  Dechen  and  Oeynhausen,  that  of  Professor  Sedgwick 
and  Sir  R.  Murchison  (Geol.  Trans.  2d  series),  Mr.  L.  A.  decker's  Memoir,  read  to 
the  Royal  Soc.  of  Edin.  20th  April,  1840,  and  Mr.  Ramsay's  Geol.  of  Arran,  1841. 
I  examined  myself  a  large  part  of  Arran  in  1836. 


588  GNEISS — HORNBLENDE-SCHIST.  [On.  XXXV 

or  superposition  in  the  members  of  this  family  ;  clay-slate,  for  example, 
having  been  often  supposed  to  hold  invariably  a  higher  geological  posi- 
tion than  mica-schist,  and  mica-schist  always  to  overlie  gneiss.  But 
although  such  an  order  may  prevail  throughout  limited  districts,  it  is 
by  no  means  universal.  To  this  subject,  however,  I  shall  again  revert,  in 
the  37th  chapter,  when  the  chronological  relations  of  the  metamorphic 
rocks  are  pointed  out. 

The  following  may  be  enumerated  as  the  principal  members  of  the 
metamorphic  class  :  —  gneiss,  mica-schist,  hornblende-schist,  clay-slate, 
chlorite-schist,  hypogene  or  metamorphic  limestone,  and  certain  kinds  of 
quartz-rock  or  quartzite. 

Gneiss. — The  first  of  these,  gneiss,  may  be  called  stratified,  or,  by  those 
who  object  to  that  term,  foliated,  granite,  being  formed  of  the  same  ma- 
terials as  granite,  ramely,  felspar,  quartz,  and  mica.  In  the  specimen 
here  figured,  the  white  layers  consist  almost  exclusively  of  granular  fel- 
spar, with  here  and  there  a  speck  of  mica  and  grain  of  quartz.  The  dark 
layers  are  composed  of  gray  quartz  and  black  mica,  with  occasionally  a 

Fig.  704. 


Fragment  of  gneiss,  natural  size:  section  made  at  right  angles  to 
the  planes  of  foliation. 

grain  of  felspar  intermixed.  The  rock  splits  most  easily  in  the  plane  of 
these  darker  layers,  and  the  surface  thus  exposed  is  almost  entirely  cov- 
ered with  shining  spangles  of  mica.  The  accompanying  quartz,  however, 
greatly  predominates  in  quantity,  but  the  most  ready  cleavage  is  deter- 
mined by  the  abundance  of  mica  in  certain  parts  of  the  dark  layer. 

Instead  of  consisting  of  these  thin  laminae,  gneiss  is  sometimes  simply 
divided  into  thick  beds,  in  which  the  mica  has  only  a  slight  degree  of 
parallelism  to  the  planes  of  stratification. 

The  term  "  gneiss,"  however,  in  geology  is  commonly  used  in  a  wider 
sense,  to  designate  a  formation  in  which  the  above-mentioned  rock  pre- 
vails, but  with  which  any  one  of  the  other  metamorphic  rocks,  and  more 
especially  hornblende-schist,  may  alternate.  These  other  members  of  the 
metamorphic  series  are,  in  this  case,  considered  as  subordinate  to  the  true 
gneiss. 

The  different  varieties  of  rock  allied  to  gneiss,  into  which  felspar  enters 
as  an  essential  ingredient,  will  be  understood  by  referring  to  what  was  said 
of  granite.  Thus,  for  example,  hornblende  may  be  superadded  to  mica, 
quartz,  and  felspar,  forming  a  syenitic  gneiss  ;  or  talc  may  be  substituted 
for  mica,  constituting  talcose  gneiss,  a  rock  composed  of  felspar,  quartz, 
and  talc,  in  distinct  crystals  or  grains  (stratified  protogine  of  the  French). 


CH.  XXXV.]  MICA-SCHIST,  CLAY-SLATE,  ETC.  589 

Hornblende-schist  is  usually  black,  and  composed  principally  of  horn- 
blende, with  a  variable  quantity  of  felspar,  and  sometimes  grains  of  quartz. 
When  the  hornblende  and  felspar  are  nearly  in  equal  quantities,  and  the 
rock  is  not  slaty,  it  corresponds  in  character  with  the  greenstones  of  the 
trap  family,  and  has  been  called  "  primitive  greenstone."  It  may  be 
termed  hornblende  rock.  Some  of  these  hornblendic  masses  may  really 
have  been  volcanic  rocks,  which  have  since  assumed  a  more  crystalline  or 
metamorphic  texture. 

Mica-schist,  or  Micaceous  schist,  is,  next  to  gneiss,  one  of  the  most 
abundant  rocks  of  the  metamorphic  series.  It  is  slaty,  essentially  com- 
posed of  mica  and  quartz,  the  mica  sometimes  appearing  to  constitute  the 
whole  mass.  Beds  of  pure  quartz  also  occur  in  this  format* on.  In  some 
districts,  garnets  in  regular  twelve-sided  crystals  form  an  integrant  part  of 
mica-schist.  This  rock  passes  by  insensible  gradations  into  clay-slate. 

Clay-slate,  or  Argillaceous  schist. — This  rock  sometimes  resembles  an 
indurated  clay  or  shale.  It  is  for  the  most  part  extremely  fissile,  often 
affording  good  roofing-slate.  Occasionally  it  derives  a  shining  and  silky 
lustre  from  the  minute  particles  of  mica  or  talc  which  it  contains.  It 
varies  from  greenish  or  bluish-gray  to  a  lead  color  ;  and  it  may  be  said  of 
this,  more  than  of  any  other  schist,  that  it  is  common  to  the  metamorphic 
and  fossiliferous  series,  for  some  clay-slates  taken  from  each  division  would 
not  be  distinguishable  by  mineral  characters  alone. 

Quartzite,  or  Quartz  rock,  is  an  aggregate  of  grains  of  quartz  which 
are  either  in  minute  crystals,  or  in  many  cases  slightly  rounded,  occurring 
in  regular  strata,  associated  with  gneiss  or  other  metamorphic  rocks. 
Compact  quartz,  like  that  so  frequently  found  in  veins,  is  also  found 
together  with  granular  quartzite.  Both  of  these  alternate  with  gneiss  or 
mica-schist,  or  pass  into  those  rocks  by  the  addition  of  mica,  or  of  felspar 
and  mica. 

Chlorite-schist  is  a  green  slaty  rock,  in  which  chlorite  is  abundant  in 
foliated  plates,  usually  blended  with  minute  grains  of  quartz,  or  sometimes 
with  felspar  or  mica ;  often  associated  with,  and  graduating  into,  gneiss 
and  clay-slate. 

Crystalline  or  Metamorphic  limestone. — This  hypogene  rock,  called  by 
the  earlier  geologists  primary  limestone,  is  sometimes  a  white  crystalline 
granular  marble,  which  when  in  thick  beds  can  be  used  in  sculpture ; 
but  more  frequently  tit  occurs  in  thin  beds,  forming  a  foliated  schist  much 
resembling  in  color  and  appearance  certain  varieties  of  gneiss  and  mica- 
schist.  When  it  alternates  with  these  rocks,  it  often  contains  some  crys- 
tals of  mica,  and  occasionally  quartz,  felspar,  hornblende,  talc,  chlorite, 
garnet,  and  other  minerals.  It  enters  sparingly  into  the  structure  of  the 
hypogene  districts  of  Norway,  Sweden,  and  Scotland,  but  is  largely  de- 
veloped in  the  Alps. 

Before  offering  any  farther  observations  on  the  probable  origin  of  the 
metamorphic  rocks,  I  subjoin,  in  the  form  of  a  glossary,  a  brief  explanation 
of  some  of  the  principal  varieties  and  their  synonyms. 


590  METAMORPHIC  EOCKS.  [On.  XXXV. 


Explanation  of  the  Names,  Synonyms,  and  Mineral  Composition  of  tht 
more  abundant  Metamorphic  Rocks. 

ACTINOLITE-SCHIST.  A  slaty  foliated  rock,  composed  chiefly  of  actinolite  (an  emer- 
ald-green mineral,  allied  to  hornblende),  with  some  admixture  of  garnet, 
mica,  and  quartz. 

AMPELITE.  Aluminous  slate  (Brongniart) ;  occurs  both  in  the  metamorphic  and 
fossiliferous  series. 

AMPHIBOLITE.     Hornblende  rock,  which  see. 

ARGILLACEOUS-SCHIST,  or  CLAY-SLATE.     See  p.  589. 

ARKOSE.  Name  given  by  Brongniart  to  a  compound  of  the  same  materials  as 
granite,  which  it  xrften  resembles  closely.  It  is  found  at  the  junction  of 
granite  with  formations  of  different  ages,  and  consists  of  crystals  of  felspar, 
quartz,  and  sometimes  mica,  which,  after  separation  from  their  original 
matrix  by  disintegration,  have  been  reunited  by  a  siliceous  or  quartzose 
cement.  It  is  often  penetrated  by  quartz  veins. 

CHIASTOLITE-SLATE  scarcely  differs  from  clay- slate,  but  includes  numerous  crystals 
of  Chiastolite  :  in  considerable  thickness  in  Cumberland.  Chiastolite  occurs 
in  long  fclender  rhomboidal  crystals.  For  composition,  see  Table,  p.  475. 

CHLORITE-SCIIIST.  A  green  slaty  rock,  in  which  chlorite,  a  green  scaly  mineral,  is 
abundant.  See  p.  589. 

CLAY-SLATE  or  ARGILLACEOUS-SCHIST.     See  p.  589* 

EURITE  has  been  already  mentioned  as  a  plutonic  rock  (p.  564),  but  occurs  also 
with  precisely  the  same  composition  in  beds  subordinate  to  gneiss  or  mica- 
slate. 

GNEISS.  A  stratified  or  foliated  rock ;  has  the  same  composition  as  granite.  See 
p.  589. 

HORNBLENDE  ROCK,  or  AMPHIBOLITE.  See  above,  p.  473.  A  member  both  of  the 
volcanic  and  metamorphic  series.  Agrees  in  composition  with  hornblende- 
schist,  but  is  not  fissile. 

HORNBLENDE-SCHIST,  or  SLATE.     Composed  of  hornblende  and  felspar.     See  p.  589. 

HORNBLENDIC  or  SYENiTic  GNEISS.     Composed  of  felspar,  quartz,  and  hornblende. 

HYPOGENE  LIMESTONE.     See  p.  589. 

MARBLE.     See  pp.  12  <fe  589. 

MICA-SCHIST,  or  MICACEOUS- SCHIST.     A  slaty  rock,  composed  of  mica  and  quartz,  in 

variable  proportions.     See  p.  589. 
MICA-SLATE.     See  MICA-SCHIST,  p.  589. 

PHYLLADE.     D'Aubuisson's  term  for  clay-slate,  from  0uAXa?,  a  heap  of  leaves. 

PRIMARY  LIMESTONE.     See  HYPOGENE  LIMESTONE,  p.  589. 

PROTOGINE.     See  TALCOSE- GNEISS,  p.  588;  when  unstratified  it  is  Talcose-granite. 

QUARTZ  ROCK,  or  QUARTZITE.  A  stratified  rock ;  an  aggregate  of  grains  of  quartz. 
See  p.  589. 

SERPENTINE  has  already  been  described  (p.  474),  because  it  occurs  in  both  divi- 
sions of  the  hypogene  series,  as  a  stratified  or  unstratified  rock. 

TALCOSE-GNEISS.     Same  composition  as  talcose-granite  or  protogine,  but  stratified 

or  foliated.     See  p.  588. 
TALCOSE-SCHIST  consists  chiefly  of  talc,  or  of  talc  and  quartz,  or  of  talc  and  fel 

spar,  and  has  a  texture  something  like  that  of  clay-slate. 


CH.  XXXV.]  METAMOKPHIC  KOCKS.  591 

Origin  of  the  Metamorphic  Strata. 

Having  said  thus  much  of  the  mineral  composition  of  the  metamorphic 
rocks,  I  may  combine  what  remains  to  be  said  of  their  structure  and  his- 
tory with  an  account  of  the  opinions  entertained  of  their  probable  origin. 
At  the  same  time,  it  may  be  well  to  forewarn  the  reader  that  we  are  here 
entering  upon  ground  of  controversy,  and  soon  reach  the  limits  where 
positive  induction  ends,  and  beyond  which  we  can  only  indulge  in  specu- 
lations. It  was  once  a  favorite  doctrine,  and  is  still  maintained  by  many, 
that  these  rocks  owe  their  crystalline  texture,  their  want  of  all  signs  of 
a  mechanical  origin,  or  of  fossil  contents,  to  a  peculiar  and  nascent  con- 
dition of  the  planet  at  the  period  of  their  formation.  The  arguments  in 
refutation  of  this  hypothesis  will  be  more  fully  considered  when  I  show, 
in  the  last  chapter  of  this  volume,  to  how  many  different  ages  the 
metamorphic  formations  are  referable,  and  how  gneiss,  mica-schist,  clay- 
slate,  and  hypogene  limestone  (that  of  Carrara,  for  example)  have  been 
formed,  not  only  since  the  first  introduction  of  organic  beings  into  this 
planet,  but  even  long  after  many  distinct  races  of  plants  and  animals  had 
passed  away  in  succession. 

The  doctrine  respecting  the  crystalline  strata,  implied  in  the  name 
metamorphic,  may  properly  be  treated  of  in  this  place ;  and  we  must 
first  inquire  whether  these  rocks  are  really  entitled  to  be  called  stratified 
in  the  strict  sense  of  having  been  originally  deposited  as  sediment  from 
water.  The  general  adoption  by  geologists  of  the  term  stratified,  as 
applied  to  these  rocks,  sufficiently  attests  their  division  into  beds  very 
analogous,  at  least  in  form,  to  ordinary  fossiliferous  strata.  This  resem- 
blance is  by  no  means  confined  to  the  existence  in  both  occasionally  of 
a  laminated  structure,  but  extends  to  every  kind  of  arrangement  which 
is  compatible  with  the  absence  of  fossils,  and  of  sand,  pebbles,  ripple- 
mark,  and  other  characters  which  the  metamorphic  theory  supposes 
to  have  been  obliterated  by  plutonic  action.  Thus,  for  example,  we 
behold  alike  in  the  crystalline  and  fossiliferous  formations  an  alternation 
of  beds  varying  greatly  in  composition,  color,  and  thickness.  We 
observe,  for  instance,  gneiss  alternating  with  layers  of  black  hornblende- 
schist,  or  of  green  chlorite-schist,  or  with  granular  quartz,  or  lime- 
stone ;  and  the  interchange  of  these  different  strata  may  be  repeated 
for  an  indefinite  number  of  times.  In  the  like  manner,  mica-schist 
alternates  with  chlorite-schist,  and  with  beds  of  pure  quartz  or  of  granu- 
lar limestone. 

We  have  already  seen  that,  near  the  immediate  contact  of  granitic 
veins  and  volcanic  dikes,  very  extraordinary  alterations  in  rocks  have 
taken  place,  more  especially  in  the  neighborhood  of  granite.  It  will  be 
useful  here  to  add  other  illustrations,  showing  that  a  texture  undis- 
tinguishable  from  that  which  characterizes  the  more  crystalline  meta- 
morphic formations  has  actually  been  superinduced  in  strata  once  fos- 
siliferous. 


592 


STEATA  IN"  CONTACT  WITH  GRANITE.       [On.  XXXY. 


In  the  southern  extremity  of  Norway  there  is  a  large  district,  on  the 
west  side  of  the  fiord  of  Christiania,  in  which  granite  or  syenite  pro- 
trudes in  mountain  masses  through  fossiliferous  strata,  and  usually  sends 
veins  into  them  at  the  point  of  contact.  The  stratified  rocks,  replete  with 
shells  and  zoophytes,  consist  chiefly  of  shale,  limestone,  and  some  sand- 
stone, and  all  these  are  invariably  altered  near  the  granite  for  a  dis- 
tance of  from  50  to  400  yards.  The  aluminous  shales  are  hardened  and 
have  become  flinty.  Sometimes '  they  resemble  jasper.  Ribboned  jasper 
is  produced  by  the  hardening  of  alternate  layers  of  green  and  chocolate- 
colored  schist,  each  stripe  faithfully  representing  the  original  lines  of  strati- 
fication. Nearer  the  granite  the  schist  often  contains  crystals  of  horn- 
blende, which  are  even  met  with  in  some  places  for  a  distance  of  several 
hundred  yards  from  the  junction  ;  and  this  black  hornblende  is  so  abun- 
dant that  eminent  geologists,  when  passing  through  the  country,  have 
confounded  it  with  the  ancient  hornblende-schist,  subordinate  to  the  great 
gneiss  formation  of  Norway.  Frequently,  between  the  granite  and  the 
hornblende  slate,  above-mentioned,  grains  of  mica  and  crystalline  felspar 
appear  in  the  schist,  so  that  rocks  resembling  gneiss  and  mica-schist  are 
produced.  Fossils  can  rarely  be  detected  in  these  schists,  and  they  are 
more  completely  effaced  in  proportion  to  the  more  crystalline  texture  of 
the  beds,  and  their  vicinity  to  the  granite.  In  some  places  the  siliceous 
matter  of  the  schist  becomes  a  granular  quartz ;  and  when  hornblende 
and  mica  are  added,  the  altered  rock  loses  its  stratification,  and  passes 
into  a  kind  of  granite.  The  limestone,  which  at  points  remote  from  the 
granite  is  of  an  earthy  texture  and  blue  color,  and  often  abounds  in 
corals,  becomes  a  white  granular  marble  near  the  granite,  sometimes 
siliceous,  the  granular  structure  extending  occasionally  upwards  of  400 
yards  from  the  junction ;  the  corals  being  for  the  most  part  obliterated, 
though  sometimes  preserved,  even  in  the  white  marble.  Both  the  al- 

Fig.  705. 


Altered  zone  of  fossiliferous  slate  and  limestone  near  granite.    Christiania. 
The  arrows  indicate  the  dip,  and  the  straight  lines  the  strike,  of  the  beds. 

tered  limestone  and  hardened  slate  contain  garnets  in  many  places, 
also  ores  of  iron,  lead,  and  copper,  with  some  silver.  These  altera- 
tions occur  equally,  whether  the  granite  invades  the  strata  in  a  line 
parallel  to  the  general  strike  of  the  fossiliferous  beds,  or  in  a  line  al 


CH.  XXXV  ALTERATIONS  OF  STRATA.  593 

right  angles  to  their  strike,  as  will  be  seen  by  the  accompanying  ground 
plan.* 

The  indurated  and  ribboned  schists  above  mentioned  bear  a  strong  re- 
semblance to  certain  shales  of  the  coal  found  at  Russel's  Hall,  near  Dud- 
ley, where  coal-mines  have  been  on  fire  for  ages.  Beds  of  shale  of  con- 
siderable thickness,  lying  over  the  burning  coal,  have  been  baked  and 
hardened  so  as  to  acquire  a  flinty  fracture,  the  layers  being  alternately 
green  and  brick-colored. 

The  granite  of  Cornwall,  in  like  manner,  sends  forth  veins  into  a  coarse 
argillaceous-schist,  provincially  termed  killas.  This  killas  is  converted 
into  hornblende-schist  near  the  contact  with  the  veins.  These  appear- 
ances are  well  seen  at  the  junction  of  the  granite  and  killas,  in  St. 
Michael's  Mount,  a  small  island  nearly  300  feet  high,  situated  in  the  bay, 
at  a  distance  of  about  three  miles  from  Penzance. 

The  granite  of  Dartmoor,  in  Devonshire,  says  Sir  H.  de  la  Beche, 
has  intruded  itself  into  the  slate  and  slaty  sandstone  called  greywacke, 
twisting  and  contorting  the  strata,  and  sending  veins  into  them.  Hence 
some  of  the  slate  rocks  have  become  "  micaceous ;  others  more  indu- 
rated, and  with  the  characters  of  mica-slate  and  gneiss ;  while  others 
again  appear  converted  into  a  hard-zoned  rock  strongly  impregnated  with 
felspar."f 

We  learn  from  the  investigations  of  M.  Dufrenoy,  that  in  the  eastern 
Pyrenees  there  are  mountain  masses  of  granite  posterior  in  date  to  the 
formations  called  lias  and  chalk  of  that  district,  and  that  these  fossiliferous 
rocks  are  greatly  altered  in  texture,  and  often  charged  with  iron-ore,  in 
the  neighborhood  of  the  granite.  Thus  in  the  environs  of  St.  Martin,  near 
St.  Paul  de  Fenouillet,  the  chalky  limestone  becomes  more  crystalline 
and  saccharoid  as  it  approaches  the  granite,  and  loses  all  trace  of  the 
fossils  which  it  previously  contained  in  abundance.  At  some  points,  also, 
it  becomes  dolomitic,  and  filled  with  small  veins  of  carbonate  of  iron,  and 
spots  of  red  iron-ore.  At  Rancie  the  lias  nearest  the  granite  is  not  only 
filled  with  iron-ore,  but  charged  with  pyrites,  tremolite,  garnet,  and  a 
new  mineral  somewhat  allied  to  felspar,  called,  from  the  place  in  the 
Pyrenees  where  it  occurs,  "  couzeranite." 

Now  the  alterations  above  described  as  superinduced*  in  rocks  by  vol- 
canic dikes  and  granite  veins  prove  incontestably  that  powers  exist  in 
nature  capable  of  transforming  fossiliferous  into  crystalline  strata — powers 
capable  of  generating  in  them  a  new  mineral  character,  similar  to,  nay, 
often  absolutely  identical  with  that  of  gneiss,  mica-schist,  and  other  strati- 
fied members  of  the  hypogene  series.  The  precise  nature  of  these  altering 
causes,  which  may  provisionally  be  termed  plutonic,  is  in  a  great  degree 
obscure  and  doubtful ;  but  their  reality  is  no  less  clear,  and  we  must 
suppose  the  influence  of  heat  to  be  in  some  way  connected  with  the  trans- 
mutation, if,  for  reasons  before  explained,  we  concede  the  igneous  origin 
of  granite. 

*  Keilhau,  Gaea  Norvegica,  pp.  61-63.  f  GeoL  Manual,  p.  479. 

38 


594  PLUTONIC  ACTION.  [On.  XXXV 

The  experiments  of  Gregory  Watt,  in  fusing  rocks  in  the  labora- 
tory, and  allowing  them  to  consolidate  by  slow  cooling,  prove  dis- 
tinctly that  a  rock  need  not  be  perfectly  melted  in  order  that  a 
re-arrangement  of  its  component  particles  should  take  place,  and  a 
partial  crystallization  ensue.*  We  may  easily  suppose,  therefore, 
that  all  traces  of  shells  and  other  organic  remains  may  be  destroyed ; 
and  that  new  chemical  combinations  may  arise,  without  the  mass 
being  so  fused  as  that  the  lines  of  stratification  should  be  wholly  ob- 
literated. 

We  must  not,  however,  imagine  that  heat  alone,  such  as  may  be  applied 
to  a  stone  in  the  open  air,  can  constitute  all  that  is  comprised  in  plutonic 
action.  We  know  that  volcanos  in  eruption  not  only  emit  fluid  lava, 
but  give  off  steam  and  other  heated  gases,  which  rush  out  in  enormous 
volume,  for  days,  weeks,  or  years  continuously,  and  are  even  disengaged 
from  lava  during  its  consolidation.  While  the  materials  of  granite,  there- 
fore, came  in  contact  with  the  fossiliferous  stratum  in  the  bowels  of  the 
earth  under  great  pressure,  the  contained  gases  might  be  unable  to  eseape ; 
yet  when  brought  into  contact  with  rocks,  they  might  pass  through  their 
pores  with  greater  facility  than  water -is  known  to  do  (p.  35).  These 
aeriform  fluids,  such  as  sulphuretted  hydrogen,  muriatic  acid,  and  car- 
bonic acid,  issue  in  many  places  from  rents  in  rocks,  which  they  have 
discolored  and  corroded,  softening  some  and  hardening  others.  If  the 
rocks  are  charged  with  water,  they  would  pass  through  more  readily ; 
for,  according  to  the  experiments  of  Henry,  water,  under  a  hydrostatic 
pressure  of  96  feet,  will  absorb  three  times  as  much  carbonic  acid  gas  as 
it  can  under  the  ordinary  pressure  of  the  atmosphere.  Although  this  in- 
creased power  of  absorption  would  be  diminished  in  consequence  of  the 
higher  temperature  found  to  exist  as  we  descend  in  the  earth,  yet  Pro- 
fessor Bischoff  has  shown  that  the  heat  by  no  means  augments  in  such  a 
proportion  as  to  counteract  the  effect  of  augmented  pressure.f  There  are 
other  gases,  as  well  as  the  carbonic  acid,  which  water  absorbs,  and  more 
rapidly  in  proportion  to  the  amount  of  pressure.  Now  even  the  most 
compact  rocks  may  be  regarded,  before  they  have  been  exposed  to  the 
air  and  dried,  in  the  light  of  sponges  filled  with  water ;  and  it  is  con- 
ceivable that  heated  gases  brought  into  contact  with  them,  at  great  depths, 
may  be  absorbed  readily,  and  transfused  through  their  pores.  Although 
the  gaseous  matter  first  absorbed  would  soon  be  condensed,  and  part 
with  its  heat,  yet  the  continual  arrival  of  fresh  supplies  from  below  might, 
in  the  course  of  ages,  cause -the  temperature  of  the  water,  and  with  it  that 
of  the  containing  rock,  to  be  materially  raised. 

M.  Fournet,  in  his  description  of  the  metalliferous  gneiss  near  Clermont, 
in  Auvergne,  states  that  all  the  minute  fissures  of  the  rock  are  quite  satu- 
rated with  free  carbonic  acid  gas ;  which  gas  rises  plentifully  from  the 
soil  there  and  in  many  parts  of  the  surrounding  country.  The  various 
elements  of  the  gneiss,  with  the  exception  of  the  quartz,  are  all  softened  ; 

*  Phil.  Trans.  1804. 

f  Poggendorf  s  Annalen,  No.  xvi.  2d  series,  vol.  iii. 


CH.  XXXV.]  ROCKS  ALTERED  BY  SUBTERRANEAN  GASES.   595 

and  new  combinations  of  the  acid  with  lime, 'iron,  and  manganese  are 
continually  in  progress.* 

Another  illustration  of  the  power  of  subterranean  gases  is  afforded  by 
the  stufas  of  St.  Calogero,  situated  in  the  largest  of  the  Lipari  Islands. 
Here,  according  to  the  description  published  by  Hoffmann,  horizontal 
strata  of  tuff,  extending  for  4  miles  along  the  coast,  and  forming  cliffs 
more  than  200  feet  high,  have  been  discolored  in  various  places,  and 
strangely  altered  by  the  "  all-penetrating  vapors."  Dark  clays  have  be- 
come yellow,  or  often  snow-white ;  or  have  assumed  a  chequered  or 
brecciated  appearance,  being  crossed  with  ferruginous  red  stripes.  In 
some  places  the  fumeroles  have  been  found  by  analysis  to  consist  partly 
of  sublimations  of  oxide  of  iron  ;  but  it  also  appears  that  veins  of  chalce- 
dony and  opal,  and  others  of  fibrous  gypsum,  have  resulted  from  these 
volcanic  exhalations.! 

The  reader  may  also  refer  to  M.  Virlet's  account  of  the  corrosion  of 
hard,  flinty,  and  jaspideous  rocks  near  Corinth  by  the  prolonged  agency 
of  subterranean  gases  ;J  and  to  Dr.  Daubeny's  description  of  the  decom- 
position of  trachytic  rocks  in  the  Solfatara,  near  Naples,  by  sulphuretted 
hydrogen  and  muriatic  .acid  gases.§ 

Although  in  all  these  instances  we  can  only  study  the  phenomena  as 
exhibited  at  the  surface,  it  is  clear  that  the  gaseous  fluids  must  have 
made  their  way  through  the  whole  thickness  of  porous  or  fissured  rocks, 
which  intervene  between  the  subterranean  reservoirs  of  gas  and  the  exter- 
nal air.  The  extent,  therefore,  of  the  earth's  crust  which  the  vapors  have 
permeated  and  are  now  permeating  may  be  thousands  of  fathoms  in  thick- 
ness, and  their  heating  and  modifying  influence  may  be  spread  through- 
out the  whole  of  this  solid  mass. 

We  learn  from  Professor  Bischoff  that  the  steam  of  a  hot  spring 
at  Aix-la-Chapelle,  although  its  temperature  is  only  from  133°  to 
167°  F.,  has  converted  the  surface  of  some  blocks  of  black  marble 
into  a  doughy  mass.  He  conceives,  therefore,  that  steam  in  the  bow- 
els of  the  earth,  having  a  temperature  equal  or  even  greater  than 
the  melting  point  of  lava,  and  having  an  elasticity  of  which  even  Pa- 
pin's  digester  can  give  but  a  faint  idea,  may  convert  rocks  into  liquid 
matter.  || 

The  above  observations  are  calculated  to  meet  some  of  the  objections 
which  have  been  urged  against  the  metamorphic  theory  on  the  ground 
of  the  small  power  of  pocks  to  conduct  heat ;  for  it  is  well  known  that 
rocks,  when  dry  and  in  the  air,  differ  remarkably  from  metals  in  this 
respect.  It  has  been  asked  how  the  changes  which  extend  merely  for  a 
few  feet  from  the  contact  of  a  dike  could  have  penetrated  through  moun- 

*  See  Principles,  Index,  "  Carbonated  Springs,"  Ac. 
f  Hoffmann's  Liparischen  Inseln,  p.  38.     Leipzig,  1832. 

J  See  Princ.  of  Geol.  ;  and  Bulletin  de  la  Soc.  G6ol.  de  France,  torn,  ii 
p.  230. 

§  See  Princ.  of  GeoL;  and  Daubeny's  Volcanos,  p.  167. 
jj  Jam.  Ed,  New  Phil.  Journ.  No.  51,  p.  43. 


596  ORIGIN"  OF  METAHORPHIC  STRUCTURE.      [On. 

tain  masses  of  crystalline  strata  several  miles  in  thickness.  Now  it  has 
been  stated  that  the  plutonic  influence  of  the  syenite  of  Norway  has  some- 
times altered  fossiliferous  strata  for  a  distance  of  a  quarter  of  a  mile,  both 
in  the  direction  of  their  dip  and  of  their  strike.  (See  fig.  705,  p.  593.) 
This  is  undoubtedly  an  extreme  case  ;  but  is  it  not  far  more  philosophical 
to  suppose  that  this  influence  may,  under  favorable  circumstances,  affect 
denser  masses,  than  to  invent  an  entirely  new  cause  to  account  for  effects 
merely  differing  in  quantity,  and  not  in  kind  ?  The  metamorphic  theory 
does  not  require  us  to  affirm  that  some  contiguous  mass  of  granite  has 
been  the  altering  power ;  but  merely  that  an  action,  existing  in  the  in- 
terior of  the  earth  at  an  unknown  depth,  whether  thermal,  hydro-thermal, 
electrical,  or  other,  analogous  to  that  exerted  near  intruding  masses  of 
granite,  has,  in  the  course  of  vast  and  indefinite  periods,  and  when  rising 
perhaps  from  a  large  heated  surface,  reduced  strata  thousands  of  yards 
thick  to  a  state  of  semi-fusion,  so  that  on  cooling  they  have  become  crys- 
talline, like  gneiss.  Granite  may  have  been  another  result  of  the  same 
action  in  a  higher  state  of  intensity,  by  which  a  thorough  fusion  has  been 
produced  ;  and  in  this  manner  the  passage  from  granite  into. gneiss  may 
be  explained. 

In  considering,  then,  the  various  data  already  enumerated,  the  forms  of 
stratification  and  lamination  in  metamorphic  rocks,  their  passage  on  the 
one  hand  into  the  fossiliferous,  and  on  the  other  into  the  plutonic  forma- 
tions, and  the  conversions  which  can  be  ascertained  to  have  occurred  in 
the  vicinity  of  granite,  we  may  conclude  that  gneiss  and  mica-schist  may 
be  nothing  more  than  altered  micaceous  and  argillaceous  sandstones,  that 
granular  quartz  may  have  been  derived  from  siliceous  sandstone,  and 
compact  quartz  from  the  same  materials.  Clay-slate  may  be  altered 
shale,  and  granular  marble  may  have  originated  in  the  form  of  ordinary 
limestone,  replete  with  shells  and  corals,  which  have  since  been  obliter- 
ated ;  and,  lastly,  calcareous  sands  and  marls  may  have  been  changed 
into  impure  crystalline  limestones. 

"  Hornblende-schist,''  says  Dr.  MacCulloch,  "  may  at  first  have  been 
mere  clay  ;  for  clay  or  shale  is  found  altered  by  trap  into  Lydian  stone,  a 
substance  differing  from  hornblende-schist  almost  solely  in  compactness 
and  uniformity  6f  texture."*  "  In  Shetland,"  remarks  the  same  author, 
"  argillaceous-schist  (or  clay-slate),  when  in  contact  with  granite,  is  some- 
times converted  into  hornblende-schist,  the  schist  becoming  first  siliceous, 
and  ultimately,  at  the  contact,  hornblende-schist."f 

The  anthracite  and  plumbago  associated  with  hypogene  rocks  may 
have  been  coal ;  for  not  only  is  coal  converted  into  anthracite  in  the 
vicinity  of  some  trap  dikes,  but  we  have  seen  that  a  like  change  has 
taken  place  generally  even  far  from  the  contact  of  igneous  roclis,  in  the 
disturbed  region  of  the  Appalachians.];  At  Worcester,  in  the  state  of 
Massachusetts,  45  miles  due  west  of  Boston,  a  bed  of  plumbago  and  im- 
pure anthracite  occurs,  interstratified  with  mica-schist.  It  is  about  2  feet 

*  Syst.  of  Geol.  vol.  i.  p.  210  f  ^id.  p.  211. 

J  &ee  above,  p.  388,  394. 


CH.  XXXV.]      'ORIGIN  OF  METAMORPHIC  STRUCTURE.  597 

in  thickness,  and  has  been  made  use  of  both  as  fuel,  and  in  the  manu 
facture  of  lead-pencils.  At  the  distance  of  30  miles  from  the  plumbago, 
there  occurs,  on  the  borders  of  Rhode  Island,  an  impure  anthracite  in 
slates,  containing  impressions  of  coal-plants  of  the  genera  Pecopteris,  Neu- 
ropteris,  Calamites,  &c.  This  anthracite  is  intermediate  in  character  be- 
tween that  of  Pennsylvania  and  the  plumbago  of  Worcester,  in  which 
last  the  gaseous  or  volatile  matter  (hydrogen,  oxygen,  and  nitrogen)  is  to 
the  carbon  only  in  the  proportion  of  3  per  cent.  .After  traversing  the 
country  in  various  directions,  I  came  to  the  conclusion  that  the  carbonif- 
erous shales  or  slates  with  anthracite  and  plants,  which  in  Rhode  Island 
often  pass  into  mica-schist,  have  at  Worcester  assumed  a  perfectly  crys- 
talline and  metamorphic  texture ;  the  anthracite  having  been  nearly  trans- 
muted into  that  state  of  pure  carbon  which  is  called  plumbago  or 
graphite.* 

It  has  been  remarked  by  M.  Delesse  that  the  minerals  developed  in 
hypogene  limestone  vary  according  to  the  degree  of  metamorphism  which 
the  rock  has  undergone.  Thus,  for  example,  where  the  structure  is  but 
slightly  crystalline,  talc,  chlorite,  serpentine,  andalusite,  and  kyanite  are 
commonly  present ;  where  it  is  more  highly  crystallized,  garnet,  horn- 
blende, Wollastonite,  dipyre,  Couzeranite,  and  some  others  appear ;  and, 
lastly,  where  the  crystallization  is  complete,  there  are  found,  in  addition 
to  many  of  the  above  minerals,  felspar,  especially  those  kinds  which  are 
richest  in  alkali,  together  with  mica.  The  same  author  observes  that,  as 
calcareous  deposits  usually  contain  some  aluminous  clay,  so  we  may  nat- 
urally expect  to  meet  with  silicates  of  alumina  in  crystalline  limestone  ; 
such  silicates,  accordingly,  are  frequent,  and  occasionally  even  pure  alumi- 
na crystallized  in  the  form  of  corundum.f 

Mr.  Dana  has  suggested  that  the  phosphoric  acid  of  phosphate  of  lime- 
and  the  fluor  of  fluor-spar,  so  often  met  with  in  crystalline  limestones,  may 
have  been  derived  from  the  remains  of  mollusca  and  other  animals ;  also 
that  graphite  (which  is  pure  carbon  in  a  crystalline  form,  with  or  without 
admixture  of  alumina,  lime,  or  iron)  may  have  been  derived  from  vegetable 
remains  imbedded  in  the  original  matrix. 

The  total  absence  of  any  trace  of  fossils  has  inclined  many  geologists 
to  attribute  the  origin  of  the  crystalline  strata  to  a  period  antecedent  to 
the  existence  of  organic  beings.  Admitting,  they  say,  the  obliteration,  in 
some  cases,  of  fossils  by  plutonic  action,  we  might  still  expect  that  traces 
of  them  would  oftener  occur  in  certain  ancient  systems  of  slate,  in  which, 
as  in  Cumberland,  some  conglomerates  occur.  But  in  urging  this  argu- 
ment, it  seems  to  have  been  forgotten  that  there  are  stratified  formations 
of  enormous  thickness,  and  of  various  ages,  and  some  of  them  very  mod- 
ern, all  formed  after  the  earth  had  become  the  abode  of  living  creatures, 
which  are,  nevertheless,  in  certain  districts,  entirely  destitute  of  all  ves- 
tiges of  organic  bodies.  In  some,  the  traces  of  fossils  may  have  been 
effaced  by  water  and  acids,  at  many  successive  periods ;  and  it  is  clear, 

*  See  Lyell,  Quart.  GeoL  Journ.  vol.  i.  p.  199. 

f  Delesse,  Bulletin  Soc.  GeoL  France,  2d  serie,  torn.  9,  p.  126.     1851. 


598  OBJECTIONS  TO  METAMORPHIC  THEOKY.       [Cn.  XXXV. 

that,  the  older  the  stratum,  the  greater  is  the  chance  of  its  being  non- 
fossiliferous,  even  if  it  has  escaped  all  metamorphic  action. 

It  has  been  also  objected  to  the  metamorphic  theory.,  that  the  chemical 
composition  of  the  secondary  strata  differs  essentially  from  that  of  the 
crystalline  schists,  into  which  they  are  supposed  to  be  convertible.*  The 
"  primary"  schists,  it  is  said,  usually  contain  a  considerable  proportion  of 
potash  or  of  soda,  which  the  secondary  clays,  shales,  and  slates  do  not, 
these  last  being  the  result  of  the  decomposition  of  felspathic  rocks,  from 
which  the  alkaline  matter  has  been  abstracted  during  the  process  of  de- 
composition. But  this  reasoning  proceeds  on  insufficient  and  apparently 
mistaken  data  \  for  a  large  portion  of  what  is  usually  called  clay,  marl, 
shale,  and  slate  does  actually  contain  a  certain,  and  often  a  considerable, 
proportion  of  alkali ;  so  that  it  is  difficult,  in  many  countries,  to  obtain  clay 
or  shale  sufficiently  free  from  alkaline  ingredients  to  allow  of  their  being 
burnt  into  bricks  or  used  for  pottery. 

Thus  the  argillaceous  shales  and  slates  of  the  Old  Red  sandstone,  in 
Forfarshire  and  other  parts  of  Scotland,  are  so  much  charged  with  alkali, 
derived  from  triturated  felspar,  that,  instead  of  hardening  when  exposed 
to  fire,  they  sometimes  melt  into  a  glass.  They  contain  no  lime,  but  ap- 
pear to  consist  of  extremely  minute  grains  of  the  various  ingredients  of 
granite,  which  are  distinctly  visible  in  the  coarser-grained  varieties,  and 
in  almost  all  the  interposed  sandstones.  These  laminated  clays  and  shales 
might  certainly,  if  crystallized,  resemble  in  composition  many  of  the  pri- 
mary strata. 

There  is  also  potash  in  fossil  vegetable  remains,  and  soda  in  the  salts 
by  which  strata  are  sometimes  so  largely  impregnated,  as  in  Patagonia. 
But  recent  analysis  may  be  said  to  have  settled  the  point  at  issue,  by 
demonstrating  that  the  carboniferous  strata  in  England,}  the  Upper  and 
Lower  Silurian  in  East  Canada^  and  the  clay-slates  (of  Cambrian  date  ?) 
in  Norway ,§  all  contain  as  much  alkali  as  is  generally  present  in  meta- 
morphic rocks. 

Another  objection  has  been  derived  from  the  alternation  of  highly 
crystalline  strata  with  others  having  a  less  crystalline  texture.  The  heat, 
it  is  said,  in  its  ascent  from  below,  must  have  traversed  the  less  altered 
schists  before  it  reached  a  higher  and  more  crystalline  bed.  In  answer 
to  this,  it  may  be  observed,  that  if  a  number  of  strata  differing  greatly 
in  composition  from  each  other  be  subjected  to  equal  quantities  of  heat, 
there  is  every  probability  that  some  will  be  more  fusible  than  others. 
Some,  for  example,  will  contain  soda,  potash,  lime,  or  some  other  ingre- 
dient capable  of  acting  as  a  flux ;  while  others  may  be  destitute  of  the 
same  elements,  and  so  refractory  as  to  be  very  slightly  affected  by  a  de- 
gree of  heat  capable  of  reducing  others  to  semi-fusion.  Nor  should  it  be 


*  Dr.  Boase,  Primary  Geology,  p.  319. 

f  H.Taylor,  Edin.  New.  Phil.  Journ.  vol.  i.  1851,  p.  140. 

j  Hunt,  Phil.  Mag.  4  ser.  vol.  vii.  p.  237. 

§  Kyersly,  Norsk,  Mag.  for  Naturvidenp.  vol  viii.  p.  172. 


CH.  XXXV.]  METAMORPEIC  THEORY.  500 

forgotten  that,  as  a  general  rule,  the  less  crystalline  rocks  do  really  occur 
in  the  upper,  and  the  more  crystalline  in  the  lower  part  of  each  meta 
morphic  series. 

Moreover,  metamorphism  must  often  begin  to  exert  its  force  long  after 
the  strata  have  assumed  a  vertical  position,  and  it  may  then  act  locally 
or  \vithin  limited  areas,  and  will  be  as  likely  to  affect  the  newer  as  the 
older  beds.  As  an  illustration  of  such  partial  conversion  into  gneiss  of 
portions  of  a  highly  inclined  set  of  beds,  I  may  cite  Sir  R.  Murchison's 
memoir  on  the  structure  of  the  Alps.  Slates  provincially  termed  "  flysch" 
(see  above,  p.  230),  overlying  the  nummulite  limestone  of  Eocene  date, 
and  comprising  some  arenaceous  and  some  calcareous  layers,  are  seen  to 
alternate  several  times  with  bands  of  granitoid  rock,  answering  in  charac- 
ter to  gneiss.*  In  this  case  heat,  or  vapor,  or  water  at  an  intensely  high 
temperature,  may  have  traversed  the  more  permeable  beds,  and  altered 
them  so  far  as  to  admit  of  an  internal  movement  and  re-arrangement  of 
the  molecules,  while  the  adjoining  strata  did  not  give  passage  to  the  same 
heat,  or  if  BO,  remained  unchanged  because  they  were  composed  of  less 
fusible  materials.  Whatever  hypothesis  we  adopt,  the  phenomena  estab- 
lish beyond  a  doubt  the  possibility  of  the  development  of  the  metamor- 
phic  structure  in  a  tertiary  deposit  in  planes  parallel  to  those  of  stratifi- 
cation. 

Whether  such  parallelism  be  the  rule  or  the  exception  in  gneiss,  mica- 
schist,  and  other  formations  of  the  same  family,  is  a  question  which  I 
shall  discuss  at  length  in  the  next  chapter. 

*  GeoL  Quart,  Jmrn.  yoL  v.  p.  211      1848. 


GOO  METAMOKPHIC  EOCKS.  [Ca  XXXVI 


CHAPTER  XXXVI. 

Origin  of  the  metamorphic  rocks,  continued — Definition  of  joints — slaty  cleavage 
and  foliation — Supposed  causes  of  these  structures — Mechanical  theory  of 
cleavage — Condensation  and  elongation  of  slate  rocks  by  lateral  pressure — 
Supposed  combination  of  crystalline  and  mechanical  forces — Lamination  of 
some  volcanic  rocks  due  to  motion — Whether  the  foliation  of  the  crystalline 
schists  be  usually  parallel  -with  the  original  planes  of  stratification — Examples 
in  Norway  and  Scotland — Foliation  in  homogeneous  rocks  may  coincide  with 
planes  of  cleavage,  and  in  uncleaved  rocks  with  those  of  stratification — Causes 
of  irregularity  in  the  planes  of  foliation. 

WE  have  already  seen  that  crystalline  forces  of  great  intensity  have 
frequently  acted  upon  sedimentary  and  fossiliferous  strata  long  subse- 
quently to  their  consolidation,  and  we  may  next  inquire  whether  the 
component  minerals  of  the  altered  rocks  usually  arrange  themselves  in 
planes  parallel  to  the  original  planes  of  stratification,  or  whether,  after 
crystallization,  they  more  commonly  take  up  a  different  position. 

In  order  to  estimate  fairly  the  merits  of  this  question,  we  must  first 
define  what  is  meant  by  the  terms  cleavage  and  foliation.  There  are 
four  distinct  forms  of  structure  exhibited  in  rocks,  namely,  stratification, 
joints,  slaty  cleavage,  and  foliation ;  and  all  these  must  have  different 
names,  even  though  there  be  cases  where  it  is  impossible,  after  care- 
fully studying  the  appearances,  to  decide  upon  the  class  to  which  they 
belong. 

Professor  Sedgwick,  whose  essay  "  On  the  Structure  of  large  Mineral 
Masses"  first  cleared  the  way  towards  a  better  understanding  of  this  diffi- 
cult subject,  observes,  that  joints  are  distinguishable  from  lines  of  slaty 
cleavage  in  this,  that  the  rock  intervening  between  two  joints,  has  no 
tendency  to  cleave  in  a  direction  parallel  to  the  planes  of  the  joints ; 
whereas  a  rock  is  capable  of  indefinite  subdivision  in  the  direction  of  its 
slaty  cleavage.  In  some  cases  where  the  strata  are  curved,  the  planes  of 
cleavage  are  still  perfectly  parallel.  This  has  been  observed  in  the  slate 
rocks  of  part  of  Wales  (see  fig.  706),  which  consist  of  a  hard  greenish 

Fig.  T06. 


Parallel  planes  of  cleavage  intersecting  curved  strata.    (Sedgwick.) 

slate.     The  true  bedding  is  there  indicated  by  a  number  of  parallel 
stripes,  some  of  a  lighter  and  some  of  a  darker  color  than  the  general 


CH.  XXXVI. ]       JOINTED  STRUCTUKE  AND   CLEAVAGE.  601 

mass.  Such  stripes  are  found  to  be  parallel  to  the  true  planes  of  strati- 
fication, wherever  these  are  manifested  by  ripple-mark,  or  by  beds  con- 
taining peculiar  organic  remains.  Some  of  the  contorted  strata  are  of  a 
coarse  mechanical  structure,  alternating  with  fine-grained  crystalline 
chloride  slates,  in  which  case  the  same  slaty  cleavage  extends  through 
the  coarser  and  finer  beds,  though  it  is  brought  out  in  greater  perfection 
in  proportion  as  the  materials  of  the  rock  are  fine  and  homogeneous.  It 
is  only  w<hen  these  are  very  coarse  that  the  cleavage  planes  entirely 
vanish.  These  planes  are  usually  inclined  at  a  very  considerable  angle 
to  the  planes  of  the  strata.  In  the  Welsh  hills,  for  example,  the  average 
angle  is  as  much  as  from  30°  to  40°.  Sometimes  the  cleavage  planes 
dip  towards  the  same  point  of  the  compass  as  those  of  stratification,  but 
more  frequently  to  opposite  points.  It  may  be  stated  as  a  general  rule, 
that  when  beds  of  coarser  materials  alternate  with  those  composed  of 
finer  particles,  the  slaty  cleavage  is  either  entirely  confined  to  the  fine- 
grained rock,  or  is  very  imperfectly  exhibited  in  that  of  coarser  texture. 
This  rule  holds,  whether  the  cleavage  is  parallel  to  the  planes  of  stratifi- 
cation or  not.* 

In  regard  to  joints,  they  are  natural  fissures  which  often  traverse  rocks 
in  straight  and  well-determined  lines.  They  afford  to  the  quarryman, 
as  Sir  R.  Murchison  observes,  when  speaking  of  the  phenomena,  as  ex- 
hibited in  Shropshire  and  the  neighboring  counties,  the  greatest  aid  in 
the  extraction  of  blocks  of  stone ;  and,  if  a  sufficient  number  cross  each 
other,  the  whole  mass  of  rock  is  split  into  symmetrical  blocks.  The 
faces  of  the  joints  are  for  the  most  part  smoother  and  more  regular  than 
the  surfaces  of  true  strata.  The  joints  are  straight-cut  chinks,  often 
slightly  open,  often  passing,  not  only  through  layers  of  successive  depo- 
sition, but  also  through  balls  of  limestone  or  other  matter  which  have 
been  formed  by  concretionary  action,  since  the  original  accumulation  of 
the  strata.  Such  joints,  therefore,  must  often  have  resulted  from  one  of 
the  last  changes  superinduced  upon  sedimentary  deposits.f 

In  the  annexed  diagram  (fig.  707),  the  flat  surfaces  of  rock  A,  B,  c, 
represent  exposed  faces  of  joints,  to  which  the  walls  of  other  joints,  j  j, 
are  parallel ;  s  s  are  the  lines  of  stratification ;  D  D  are  lines  of  slaty 
cleavage,  which  intersect  the*  rock  at  a  considerable  angle  to  the  planes 
of  stratification.  J 

In  the  Swiss  and  Savoy  Alps,  as  Mr.  Bakewell  has  remarked,  enormous 
masses  of  limestone  are  cut  through  so  regularly  by  nearly  vertical  part- 
ings, and  these  joints  are  often  so  much  more  conspicuous  than  the  seams 
of  stratification,  that  an  inexperienced  observer  will  almost  inevitably 
confound  them,  and  suppose  the  strata  to  be  perpendicular  in  places 
where,  in  fact,  they  are  almost  horizon tal.( 

Now   such  joints  are  supposed  to  be  analogous  to  the  partings  which 

*  Geol.  Trans.  2d  series,  voL  iii.  p.  461. 

f  Silurian  System,  p.  246. 

\  Introduction  to  Geology,  chap.  iv. 


602  JOINTED  STKUCTUEE  AND   CLEAVAGE.       [Cn.  XXXVL 

Fig.  707. 


Stratification,  joints,  and  cleavage. 
(From  Murchison's  Silurian  System,  p.  245.) 

separate  volcanic  and  plutonic  rocks  into  cuboidal  and  prismatic  masses. 
On  a  small  scale  we  see  clay  and  starch,  when  dry,  split  into  similar 
shapes ;  this  is  often  caused  by  simple  contraction,  whether  the  shrinking 
be  due  to  the  evaporation  of  water,  or  to  a  change  of  temperature. 
It  is  well  known  that  many  sandstones  and  other  rocks  expand  by  the 
application  of  moderate  degrees  of  heat,  and  then  contract  again  on 
cooling ;  and  there  can  be  no  doubt  that  large  portions  of  the  earth's 
crust  have,  in  the  course  of  past  ages,  been  subjected  again  and  again  to 
very  different  degrees  of  heat  and  cold.  These  alternations  of  temper- 
ature have  probably  contributed  largely  to  the  production  of  joints  in 
rocks. 

In  some  countries,  as  in  Saxony,  where  masses  of  basalt  rest  on  sand- 
stone, the  aqueous  rock  has,  for  the  distance  of  several  feet  from  the  point 
of  junction,  assumed  a  columnar  structure  similar  to  that  of  the  trap. 
In  like  manner  some  hearthstones,  after  exposure  to  the  heat  of  a  furnace 
without  being  melted,  have  become  prismatic.  Certain  crystals  also 
acquire,  by  the  application  of  heat,  a  new  internal  arrangement,  so  as  to 
break  in  a  new  direction,  their  external  form  remaining  unaltered. 

Professor  Sedgwick,  speaking  of  the  planes  of  slaty  cleavage,  where 
they  are  decidedly  distinct  from  those  of  sedimentary  deposition,  declared 
in  the  essay  before  alluded  to,  his  opinion '  that  no  retreat  of  parts,  no 
contraction  in  the  dimensions  of  rocks  in  passing  to  a  solid  state,  can 
account  for  the  phenomenon.  He  accordingly  referred  it  to  crystalline  or 
polar  forces  acting  simultaneously,  and  somewhat  uniformly,  in  given 
directions,  on  large  masses  having  a  homogeneous  composition. 

Sir  John  Herschel,  in  allusion  to  slaty  cleavage,  has  suggested,  "  that 
if  rocks  have  been  so  heated  as  to  allow  a  commencement  of  crystalli- 
zation,— that  is  to  say,  if  they  have  been  heated  to  a  point  at  which 
the  particles  can  begin  to  move  amongst  themselves,  or  at  least  on  their 
own  axes,  some  general  law  must  then  determine  the  position  in  which 
these  particles  will  rest  on  cooling.  Probably,  that  position  will  have 
some  relation  to  the  direction  in  which  the  heat  escapes.  Now,  when 
all,  or  a  majority  of  particles  of  the  same  nature  have  a  general  tendency 


CH.  XXXVL]  SLATY   CLEAVAGE.  603 

to  one  position,  that  must  of  course  determine  a  cleavage-plane.  Thus 
we  see  the  infinitesimal  crystals  of  fresh  precipitated  sulphate  of  barytes, 
and  some  other  such  bodies,  arrange  themselves  alike  in  the  fluid  in  which 
they  float ;  so  as,  when  stirred,  all  to  glance  with  one  light,  and  give  the 
appearance  of  silky  filaments.  Some  soils  of  soap,  in  which  insoluble 
margarates*  exist,  exhibit  the  same  phenomenon  when  mixed  with 
water  ;  and  what  occurs  in  our  experiments  on  a  minute  scale  may  occur 
in  nature  on  n  great  one."  f 

Professor  Phillips  has  remarked,  that  in  some  slaty  rocks  the  form  of 
the  outline  of  fossil  shells  and  trilobites  has  been  much  changed  by  dis- 
tortion, which  has  taken  place  in  a  longitudinal,  transverse,  or  oblique 
direction.  This  change,  he  adds,  seems  to  be  the  result  of  a  "  creeping 
movement"  of  the  particles  of  the  rock  along  the  planes  of  cleavage,  its 
direction  being  always  uniform  over  the  same  tract  of  country,  and  its 
amount  in  space  being  sometimes  measurable,  and  being  as  much  as  a 
quarter  or  even  half  an  inch.  The  hard  shells  are  not  affected,  but  only 
those  which  are  thin.J  Mr.  D.  Sharpe,  following  up  the  same  line  of  in- 
quiry, came  to  the  conclusion,  that  the  present  distorted  forms  of  the 
shells  in  certain  British  slate  rocks  may  be  accounted  for,  by  supposing 
that  the  rocks  in  which  they  are  imbedded  have  undergone  compression 
in  a  direction  perpendicular  to  the  planes  of  cleavage,  and  a  correspond- 
ing expansion  in  the  direction  of  the  dip  of  the  cleavage. § 

More  recently  (July,  1853),  Mr.  Sorby  has  demonstrated  the  great 
extent  to  which  this  mechanical  theory  is  applicable  to  the  slate  rocks 
of  North  Wales  and  Devonshire,!  districts  where  the  amount  of  change 
in  dimensions  can  be  tested  and  measured  by  comparing  the  different 
effects  exerted  by  lateral  pressure  on  alternating  beds  of  finer  and  coarser 
materials.  Thus,  for  example,  in  the  accompanying  figure  (fig.  708),  it 
will  be  seen  that  the  sandy  bed  df,  which  has  offered  greater  resistance, 
has  been  sharply  contorted,  while  the  fine-grained  strata,  a,  6,  c,  hare 
remained  comparatively  unbent.  The  points  d  and/  in  the  stratum  d  f 
must  have  been  originally  four  times  as  far  apart  as  they  are  now.  They 
have  been  forced  so  much  nearer  to  each  other,  partly  by  bending,  and 
partly  by  becoming  elongated  in  the  direction  of  what  may  be  called 
the  longer  axes  of  their  contortions ;  and  lastly,  to  a  certain  small  amount, 
by  condensation.  The  chief  result  has  obviously  been  due  to  the  bend- 
ing ;  but,  in  proof  of  elongation,  it  will  be  observed  that  the  thickness 
of  the  bed  c?/is  now  about  four  times  greater  in  those  parts  lying  in  the 
main  direction  of  the  flexures  than  in  a  plane  perpendicular  to  them : 

*  Margaric  acid  is  an  oleaginous  acid,  formed  from  different  animal  and  vege- 
table fatty  substances.  A  margarate  is  a  compound  of  this  acid  with  soda, 
potash,  or  some  other  base,  and  is  so  named  from  its  pearly  lustre. 

f  Letter  to  the  author,  dated  Cape  of  Good  Hope,  Feb.  20,  1836. 

\  Report,  Brit.  Assoc.,  Cork,  1843,  Sect  p.  60. 

§  Quart.  GeoL  Journ.  voL  iii.  p.  87.     1847. 

|  On  the  Origin  of  Slaty  Cleavage,  by  H.  C.  Sorby,  Edinb.  Kew  PhiL  Journ. 
1853,  vol.  Iv.  p.  137. 


604 


SLATE  EOCK  OF  NORTH  DEVON.  [On.  XXXVL 


Fig.  708 


and  the  same  bed  exhibits  cleavage- 
planes  in  the  direction  of  the  great- 
est movement,  although  they  are 
much  fewer  than  in  the  slaty  strata 
above  and  below. 

Above  the  sandy  bed  d  /,  the 
stratum  c  is  somewhat  disturbed, 
while  the  next  bed  b  is  much  less 
so,  and  a  not  at  all  ;  yet  all  these 
beds,  c,  6,  and  a,  must  have  under- 
gone an  equal  amount  of  pressure 
with  d,  the  points  a  and  g  having 
approximated  as  much  towards 
each  other  as  have  d  and  /.  The 
same  phenomena  are  also  repeated 
in  the  beds  below  df,  and  might 
have  been  shown,  had  the  section 
been  extending  downwards.  Hence 
it  appears  that  the  finer  beds  have 
been  squeezed  into  a  fourth  of  the 
space  they  previously  occupied, 
partly  by  condensation,  or  the  closer 
packing  of  their  ultimate  particles 
(which  has  given  rise  to  the  great 
specific  gravity  of  such  slates),  and 
partly  by  elongation  in  the  line  of  (Drawn  by  H.  c.  Sorby.) 

the   dip   of  the    cleavage,  Of  which    Vertical  section  of  slate  rock  in  the  cliffs 
.        .  near  Ilfracombe,  North  Devon. 

the  general  direction  is  perpendicu- 

.  .      J        .,  J  ,  //mi 

lar  to  that  of  the  pressure.    "  These 

,-,  .      -XT     j.i_ 

and  numerous  Other  Cases  m  North 

Devon   are   analogous,"    says   Mr. 

Sorby,  "to  what  would  occur  if  a 

strip  of  paper  were  included  in  a 

mass  of  some  soft  plastic  material  which  would  readily  change  its  di- 

mensions.    If  the  whole  were  then  compressed  in  the  direction  of  the 

length   of    the   strip   of    paper,   it   would   be   bent   and   puckered   up 

into  contortions,  whilst  the  plastic   material   would  readily  change  its 

dimensions  without   undergoing   such   contortions;  and   the   difference 

in  distance  of  the  ends  of  the  paper,  as  measured  in  a  direct  line  or 

along  it,  would  indicate  the  change  in  the  dimensions  of  the  plastic 

material." 

The  student  will  readily  conceive  that,  when  the  shape  of  a  fossil  or 
of  a  crystal  of  some  mineral,  or  of  a  spheroidal  concretion,  has  been 
altered  by  lateral  pressure,  the  new  forms  which  they  assume  respect- 
ively will  vary  according  to  whether  they  have  yielded  in  one  or  more 
directions.  They  may  have  been  drawn  out  solely  in  the  direction  of  the 


Scale  one 


to  one  foot- 


ai  k  ci  e-    Fine-grained  slates,  the  stratifica- 
tion  being  shown  partly  by  lighter  or  dark- 

»»  ditoent  degrec3  of 


Co.  XXXVI]          CONDENSATION  OF  SLATE  EOCKS.  605 

dip  of  the  cleavage,  or  they  may  have  yielded  in  a  plane  perpendicular 
to  that  dip,  or  they  may  have  undergone  both  these  movements.  By 
microscopic  examination  of  minute  crystals,  and  by  other  observations 
too  minute  to  be  detailed  here,  Mr.  Sorby  comes  to  the  conclusion  that 
the  absolute  condensation  of  the  slate  rocks  amounts  upon  an  average 
to  about  one  half  their  original  volume.  This  must  have  resulted  chiefly 
from  the  forcing  of  the  particles  more  closely  together,  so  as  to  fill 
up  the  spaces  left  between  them,  when  they  only  touched  each  other. 
The  rest  of  the  change  has  been  due  to  elongation,  which  has  produced 
slaty  cleavage. 

Most  of  the  scales  of  mica  occurring  in  certain  slates  examined  by 
Mr.  Sorby,  lie  in  the  plane  of  cleavage ;  whereas  in  a  similar  rock  not 
exhibiting  cleavage,  they  lie  with  their  longer  axes  in  all  directions. 
May  not  their  position  in  the  slates  have  been  determined  by  the 
movement  of  elongation  before  alluded  to  1  To  illustrate  this  theory, 
some  scales  of  oxide  of  iron  were  mixed  with  soft  pipe-clay,  in  such  a 
manner  that  they  inclined  in  all  directions.  The  dimensions  of  the  mass 
were  then  changed  artificially  to  a  similar  extent  to  what  has  occurred 
in  slate  rocks,  and  the  pipe-clay  was  then  dried  and  baked.  When  it 
was  afterwards  rubbed  to  a  flat  surface  perpendicular  to  the  pressure  and 
in  the  line  of  elongation,  or  in  a  plane  corresponding  to  that  of  the  dip 
of  cleavage,  the  particles  were  found  to  have  become  arranged  in  the 
same  manner  as  in  natural  slates,  and  the  mass  admitted  of  easy  fracture 
into  thin  flat  pieces  in  the  plane  alluded  to,  whereas  it  would  not  yield 
in  that  perpendicular  to  the  cleavage.* 

This  experiment  may  lend  countenance  to  the  opinion  that  the  lamina- 
tion of  basalt  and  trachyte,  and  even  of  some  kinds  of  gneiss,  and  the 
grain  of  certain  granites,  may  all  have  been  determined  by  a  mechanical 
cause,  a  movement  having  taken  place  after  the  development  of  crystals 
in  the  pasty  mass. 

Mr.  Scrope,  in  his  description  of  the  Ponza  Islands,  ascribed  "  the 
zoned  structure  of  the  Hungarian  perlite  (a  semi-vitreous  trachyte) 
to  its  having  subsided,  in  obedience  to  the  impulse  of  its  own  gravity, 
down  a  slightly  inclined  plane,  while  possessed  of  an  imperfect  fluidity. 
In  the  islands  of  Ponza  and  Palmarola,  the  direction  of  the  zones  is  more 
frequently  vertical  than  horizontal,  because  the  mass  was  impelled  from 
below  upwards.f  In  like  manner,  Mr.  Darwin  attributes  the  lamination 
and  fissile  structure  of  volcanic  rocks  of  the  trachytic  series,  including 
some  obsidians  in  Ascension,  Mexico,  and  elsewhere,  to  their  having 
moved,  when  liquid,  in  the  direction  of  the  laminae.  The  zones  consist 
sometimes  of  layers  of  air-cells  drawn  out  and  lengthened  in  the  supposed 
direction  of  the  moving  mass.  He  compares  this  division  into  parallel 
zones,  thus  caused  by  the  stretching  of  a  pasty  mass  as  it  flowed  slowly 
onwards,  to  the  zoned  or  ribboned  structure  of  ice,  which  Professor 

*  Sorby,  as  cited  above,  p.  610,  note.       f  Geol.  Trans.  2d  ser.  vol.  ii.  p.  227. 


606  FOLIATION   OF   CRYSTALLINE  ROCKS.      [Cn.  XX  XVI 

James  Forbes  has  so  ably  explained,  showing  that  it  is  due  to  the  fissuring 
of  a  viscous  body  in  motion.* 

Whatever  be  the  cause,  the  result,  observes  Darwin,  is  well  worthy  the 
attention  of  geologists  ;  for  in  a  volcanic  rock  of  the  trachytic  series  in 
Ascension  layers  are  seen  often  of  extreme  tenuity,  even  as  thin  as  hairs, 
and  of  different  colors,  alternating  again  and  again,  some  of  them  com- 
posed of  crystals  of  quartz  and  diopside  (a  kind  of  augite),  others  of 
black  augitic  specks  with  granules  of  oxide  of  iron ;  and  lastly,  others 
of  crystalline  felspar.  It  is  supposed  in  this  case  that  the  crystal- 
lizing force  acted  more  freely  in  the  direction  of  the  planes  of  cleav- 
age, produced  when  the  pasty  mass  was  stretched,  whether  because 
confined  vapors  were  enabled  to  spread  themselves  through  the  minute 
fissures,  or  because  the  ultimate  molecules  had  more  freedom  of  motion 
along  the  planes  of  less  tension,  or  for  some  other  reasons  not  yet  under- 
stood. 

After  studying,  in  1835,  the  crystalline  rocks  of  South  America,  Mr. 
Darwin  proposed  the  term  foliation  for  the  laminae  or  plates  into  which 
gneiss,  mica-schist,  and  other  crystalline  rocks  are  dh'ided.  Cleavage, 
he  observes,  may  be  applied  to  those  divisional  planes  which  render  a 
rock  fissile,  although  it  may  appear  to  the  eye  quite  or  nearly  homo- 
geneous. Foliation  may  be  used  for  those  alternating  layers  or  plates  of 
different  mineralogical  nature  of  which  gneiss  and  other  metamorphic 
schists  are  composed.  The  cleavage  planes  of  the  clay-slate  in  Terra  del 
Fuego  and  Chili  preserve  a  uniform  strike  for  hundreds  of  miles  in  regions 
whore  these  planes  are  quite  distinct  from  stratification.  In  the  same 
country  the  planes  of  foliation  of  the  mica-schist  and  gneiss  are  parallel 
to  the  cleavage  of  the  clay-slate.  Hence,  we  are  tempted,  at  first  sight, 
to  infer  that  some  common  cause  or  process,  and  that  cause  not  con- 
nected with  sedimentary  deposition,  has  impressed  cleavage  on  the  one 
set  of  rocks  and  foliation  on  the  other.  But  such  an  inference  can  only 
be  legitimately  drawn  in  those  rare  cases  where  we  are  able,  by  a  con- 
tinuous section,  to  prove  that  not  only  the  strike,  but  the  dip  of  the  slaty 
cleavage  on  the  one  hand,  and  of  the  foliation  on  the  other,  precisely 
coincide  ;  the  cleavage  at  the  same  time  not  being  parallel  to  the  strati- 
fication in  the  slate  rock.  In  some  examples  cited  by  Mr.  Darwin,  in 
Terra  del  Fuego,  the  Chonos  Islands,  and  La  Plata,  this  uniformity  of  dip 
seems  to  have  been  traced  in  a  manner  as  satisfactory  as  the  nature  of 
such  evidence  will  allow.  But  we  must  be  on  our  guard  against  a 
source  of  deception  which  may  mislead  us  in  this  chain  of  reasoning. 
We  are  informed  that  in  South  America,  as  in  other  countries,  the  strike 
of  the  cleavage  in  clay-slate  conforms  to  the  axis  of  elevation  of  the  rocks 
in  the  same  districts.  Hence  it  must  follow  that  the  folia  of  gneiss, 
mica-schist,  limestone,  and  other  crystalline  rocks,  even  if  they  strictly 
coincide  with  the  planes  of  original  stratification,  will  run  in  the  same 
direction  as  the  strike  of  the  slaty  cleavage ;  for  the  true  strata  always 

*  Darwin,  Volcanic  Islands,  pp.  69,  70. 


CH.  XXXVI]  FOLIATION   AXD   CLEAVAGE.  607 

dip  at  right  angles  to  the  axis  of  elevation,  and  are  parallel  to  it  in  their 
strike.  No  argument,  therefore,  can  be  drawn  in  favor  of  a  common 
origin  from  uniformity  of  strike  in  the  slaty  and  foliated  rocks ;  for  we 
require,  in  addition,  coincidence  of  dip  ;  and  such  is  the  variability  of  the 
dip  both  of  the  slates  and  folia  as  to  render  this  kind  of  proof  very  diffi- 
cult to  obtain. 

That  the  foliation  of  the  crystalline  schists  in  Norway  accords  very 
generally  with  the  planes  of  original  stratification  is  a  conclusion  long 
since  espoused  by  Keilhau.*  Numerous  observations  made  by  Mr.  David 
Forbes  in  the  same  countiy  (the  best  probably  in  Europe  for  studying 
such  phenomena  on  a  grand  scale)  confirm  Keilhau's  opinion  ;  for  the  dip 
of  the  Silurian  and  fossiliferous  strata  where  they  pass  into  the  metamor- 
phic  agrees  with  the  foliation  of  the  contiguous  gneiss,  mica-schist,  and 
crystalline  limestone.  So  also  in  Scotland  Mr.  D.  Forbes  has  pointed  out 
a  striking  case  where  the  foliation  is  identical  with  the  lines  of  stratifica- 
tion in  rocks  well  seen  near  Crianlorich  on  the  road  to  Tyndrum,  about 
8  miles  from  Inverarnon,  in  Perthshire.  There  is  in  that  locality  a  blue 
limestone  foliated  by  the  intercalation  of  small  plates  of  white  mica,  so 
that  the  rock  is  often  scarcely  distinguishable  in  aspect  from  gneiss 
or  mica-schist.  The  stratification  is  shown  by  the  large  beds  and 
colored  bands  of  limestone  all  dipping,  like  the  foila,  at  an  angle  of  32 
degrees  N.  E.f 

In  stratified  formations  of  every  age  we  see  layers  of  siliceous  sand 
with  or  without  mica,  alternating  with  clay,  with  fragments  of  shells  or 
corals,  or  with  seams  of  vegetable  matter,  and  we  should  expect  the  mu- 
tual attraction  of  like  particles  to  favor  the  crystallization  of  the  quartz, 
or  mica,  or  felspar,  or  carbonate  of  lime,  along  the  planes  of  original  de- 
position, ratter  than  in  planes  placed  at  angles  of  20  or  40  degrees  to 
those  of  stratification. 

In  Patagonia,  a  series  of  thin  sedimentary  layers  of  tuff  were  observed 
by  Mr.  Darwin  to  have  become  porphyritic,  first  where  least  altered, 
by  a  process  of  aggregation,  small  patches  of  clay  appearing  to  b« 
shortened  into  almond-shaped  concretions,  which  in  those  places  where 
they  were  more  changed  had  become  crystals  of  felspar,  having  their 
longer  axes  parallel  to  each  other.  In  other  associated  strata,  grains 
of  quartz  had  in  like  manner  aggregated  into  nodules  ot  crystalline 
quartz.  J 

May  we  not,  then,  presume  that  in  rocks  where  no  cleavage  has 
intervened,  foliation  and  the  planes  of  stratification  will  usually  coincide, 
as  in  all  cases  where  cleavage  happens  (as  in  the  writing-slates  of  the 
Niesen  on  the  Lake  of  Thun  in  Switzerland,  containing  fucoids)  to  agree 
with  the  original  planes  of  sedimentary  deposition  ?  Mr.  Darwin  con- 
ceives that  "  foliation  may  be  the  extreme  result  of  the  process  of  which 

»  Norske  Mag.  BTaturvidsk.  vol.  i.  p.  71. 

f  Memoir  read  before  the  Geol.  Soc.,  London,  Jan.  31,  1855. 

j  South  America,  p.  149. 


608  FOLIATION   AND   CLEAVAGE.  [On.  XXXVI. 

cleavage  is  the  first  effect ;"  or,  at  any  rate,  that  the  crystalline  force 
may  have  been  most  energetic  in  the  direction  of  cleavage.  As  bearing 
on  this  view,  he  says,  "  I  was  particularly  struck  in  the  eastern  parts  of 
Terra  del  Fuego  with  the  fact  that  the  fine  laminse  of  clay-slate,  where 
they  cut  straight  through  the  bands  of  stratification,  and  therefore  indis- 
putably true  cleavage-planes,  differ  slightly  from  one  another  in  their 
grayish  and  greenish  tints  of  color,  as  also  in  their  compactness, 
and  in  some  laminae  having  a  more  jrtspery  appearance  than  others. 
This  fact  shows  that  the  same  cause  which  has  produced  the  highly 
fissile  structure  has  altered  in  a  slight  degree  the  mineralogical  char- 
acter of  the  rock  in  the  same  planes."*  As  one  step  farther  towards 
tracing  a  passage  from  planes  of  cleavage  to  those  of  foliation,  Pro- 
fessor Sedgwick  observes  that  in  North  Wales  the  surfaces  of  slates 
are  sometimes  coated  over  with  chlorite,  "  the  crystals  of  which 
have  not  only  defined  the  cleavage  planes  but  struck  through  the 
whole  mass  of  the  rock."f  So  also,  says  Mr.  Darwin,  in  some  places 
in  South  America  crystals  of  epidote  and  of  mica  coat  the  planes  of 


Mr.  D.  Sharpe  inferred  from  observations  made  by  him  in  the  High- 
lands of  Scotland,  in  1851,  that  the  foliation  of  the  gneiss  and  mica-schist 
are  upon  the  whole  parallel  to  one  another,  but  have  no  connection  with 
any  original  planes  of  stratification  ;  and  he  also  conceives  that  the  planes 
both  of  cleavage  and  foliation  in  the  Grampians  and  in  the  region  of 
Mont  Blanc  in  Switzerland  (which  last  he  examined  in  1854)  are  parts  of 
great  curves  or  anticlinal  axes  of  considerable  regularity .J  In  like  man- 
ner in  South  America  the  cleavage  planes  of  the  clay-slate  had  been  sus- 
pected by  Mr.  Darwin,  notwithstanding  their  varying  and  opposite  dips, 
to  be  parts  of  large  curves  or  foldings,  having  their  summits  cut  off  and 
worn  down.§ 

There  seems  to  be  no  difficulty  in  imagining  that  in  rocks  of  homo- 
geneous composition  the  foliation  may  take  place  along  planes  previously 
caused  by  the  elongation  of  the  materials  along  the  dip  of  the  cleavage ; 
for  experienced  geologists  have  been  at  a  loss  to  decide  in  many  coun- 
tries which  of  two  sets  of  divisional  planes  were  referable  to  cleavage, 
and  which  to  stratification ;  and  after  much  doubt,  have  discovered 
that  they  had  at  first  mistaken  the  lines  of  cleavage  for  those  of  deposi- 
tion, because  the  former  were  by  far  the  most  marked  of  the  two.  Now 
if  such  slaty  masses  should  become  highly  crystalline,  and  be  converted 
into  gneiss,  hornblende- schist,  or  any  other  member  of  the  hypogene 
class,  the  cleavage  planes  would  be  more  likely  to  remain  visible  than 
those  of  stratification.  Professor  Henslow  had  noticed,  so  long  ago  as 
the  year  1821,  that  the  lamination  of  the  chloritic  and  other  crystalline 


*  Geol.  Observ.  on  South  America,  p.  155. 

f  Sedgwick,  Geol.  Trans.  2d  ser.  vol.  iii.  p.  471. 

\  D.  Sharpe,  Phil.  Trans.  1852,  and  Geol.  Quart.  Journ.  No.  41,  1855. 

§  Darwin,  S.  America,  p.  155. 


CH.  XXXVI]  IRREGULARITIES  IX   FOLIATIOX.  609 

schists  in  Anglesea  was  approximately  in  the  planes  of  bedding ;  and 
Professor  Ramsay,  in  1841,  observed  the  same  in  regard  to  the  gneiss 
and  mica-schist  of  Arran.  The  last-cited  geologist  says,  in  reference  to 
Anglesea,  that  the  metamorphism  probably  took  place  when  the  Lower 
Silurian  volcanos  were  in  activity,  and  therefore  long  before  the  cleavage 
of  the  Welsh  rocks ;  for  the  cleavage  of  the  latter  affects  in  common  the 
Lower  Silurian  and  the  Cambrian  strata.  In  the  same  memoir  he  adds, 
when  referring  to  Mr.  Darwin's  theory  of  foliation,  "  that  if  the  rocks  be 
uncleaved  when  metamorphism  occurs,  the  foliation  planes  will  be  apt 
to  coincide  with  those  of  bedding ;  but  if  intense  cleavage  has  preceded, 
then  we  may  expect  that  the  planes  of  foliation  will  lie  in  the  planes  of 
cleavage."* 

From  what  I  have  myself  seen  in  the  Grampians,  both  in  Forfarshire 
and  Perthshire,  I  have  always  concluded  that  MacCulloch  was  correct  in 
the  opinion  that  gneiss  and  mica-schist  may  be  considered  as  stratified 
rocks,  and  that  certain  beds  of  pure  quartz,  one  or  two  feet  thick,  which 
run  for  miles  in  the  strike  of  their  foliation,  as  well  .vs  the  intercala- 
tion of  masses  of  limestone,  and  of  chloritic,  actinolitic,  and  horn- 
blende schists,  all  indicate  the  planes  of  original  stratification.  At 
the  same  time,  I  fully  admit  that  the  alternate  layers  of  quartz, 
or  of  mica  and  quartz,  of  felspar,  or  of  mica  and  felspar,  or  of  car- 
bonate of  lime,  are  more  distinct,  in  certain  metamorphic  rocks,  than 
the  ingredients  composing  alternate  layers  in  most  sedimentary  de- 
posits, so  that  similar  particles  must  be  supposed  to  have  exerted  a 
molecular  attraction  for  each  other,  and  to  have  congregated  together 
in  layers  more  distinct  in  mineral  composition  than  before  they  were 
crystallized. 

We  have  seen  how  much  the  original  planes  of  stratification  may  be 
interfered  with  or  even  obliterated  by  concretionary  action  in  deposits 
still  retaining  their  fossils,  as  in  the  case  of  the  magnesian  limestone 
(see  p.  37).  Hence  we  must  expect  to  be  frequently  baffled  when  we 
attempt  to  decide  whether  the  foliation  does  or  does  not  accord  with  that 
arrangement  which  gravitation,  combined  with  current-action,  imparted 
to  a  deposit  from  water.  Moreover,  when  we  look  for  stratification  in 
crystalline  rocks,  we  must  be  on  our  guard  not  to  expect  too  much  reg- 
ularity. The  occurrence  of  wedge-shaped  masses,  such  as  belong  to 
coarse  sand  and  pebbles, — diagonal  lamination  (see  p.  16), — ripple-mark, 
— unconformable  stratification  (p.  61), — the  fantastic  folds  produced  by 
lateral  pressure, — faults  of  various  width, — intrusive  dikes  of  trap, — or- 
ganic bodies  of  diversified  shapes, — and  other  causes  of  unevenness  in  the 
planes  of  deposition,  both  on  the  small  and  on  the  large  scale,  will  inter- 
fere with  parallelism.  If  complex  and  enigmatical  appearances  did  not 
present  themselves,  it  would  be  a  serious  objection  to  the  metamorphic 
theory. 

In  the  accompanying  diagram  I  have  represented  carefully  the  lami- 

*  Geol.  Quart.  Journ.  1853,  vol.  ix.  p.  172. 
39 


610 


LAMINATION  OF   "  CLAY-SLATE."          [Ca  XXXVI 


Lamiiuition  of  clay-slat«,  Montagne  de  Seguinat, 
near  Gavarnie,  in  the  Pyrenees. 


nation    of    a    coarse    argillaceous  Fig.  709. 

schist  which  I  examined  in  1830 
in  the  Pyrenees.  In  part  it  ap- 
proaches in  character  to  a  green 
and  blue  roofing-slate,  while  part 
is  extremely  quartzose,  the  whole 
mass  passing  downwards  into  mi- 
caceous schist.  The  vertical  sec- 
tion here  exhibited  is  about  3  feet 
in  height,  and  the  layers  are 
sometimes  so  thin  that  fifty  may 

be  counted  in  the  thickness  of  an  inch.     Some  of  them  consist  of  pure 
quartz. 

There  is  a  resemblance  in  such  cases  to  the  diagonal  lamination  which 
we  see  in  sedimentary  rocks,  even  though  the  layers  of  quartz  and  of 
mica,  or  of  felspar  and  other  minerals,  may  be  more  distinct  in  alternating 
folia  than  they  were  originally. 

M.  Elie  de  Beaumont,  while  he  regards  the  greater  part  of  the  gneiss 
and  mica-schist  of  the  Alps  as  sedimentary  strata  altered  by  plutonic 
action,  still  conceives  that  some  of  the  Alpine  gneiss  may  have  been 
erupted,  or,  in  other  words,  may  be  granite  drawn  out  into  parallel  laminee 
in  the  manner  of  trachyte  as  above  alluded  to.* 

If  the  mass  were  squeezed  and  elongated  in  a  certain  direction  after 
crystals  of  mica,  talc,  or  other  scaly  minerals  were  developed,  these  may 
perhaps  have  arranged  themselves  in  planes  parallel  to  those  of  move- 
ment, and  a  similar  process  may  account  for  what  the  quarry  men  call 
"  the  grain"  -in  some  granites,  or  a  tendency  to  split  in  one  direction 
more  freely  than  in  another.  But,  as  a  general  rule,  the  fusion  of  the 
crystalline  schists  does  not  appear  to  have  gone  so  far  as  to  allow  of 
motion  analogous  to  that  of  lava  or  granite,  and  for  this  reason  rocks  of 
this  class  do  not  send  veins  into  surrounding  rocks.  In  the  next  chapter 
we  may  inquire  at  how  many  distinct  periods  the  hypogene  or  rnetamor- 
phic  schists  can  be  proved  to  have  originated,  and  why  for  so  long  a  time 
the  earlier  geologists  regarded  them  as  entitled  to  the  name  of  "  primi- 
tive." 


*  Bulletin  Soc.  Geol.  de  France,  2e  s6r.  vol.  iv.  p.  1301. 


CIT.  XXXVII.1  AGE   OF   METAMORPHIC  ROCKS.  611 


CHAPTER  XXXVH. 

ON    THE    DIFFERENT    AGES    OF   THE    METAMORPHIC    ROCKS. 

Age  of  each  set  of  metamorphic  strata  twofold — Test  of  age  by  fossils  and  min- 
eral character  not  available — Test  by  superposition  ambiguous — Conversion 
of  dense  masses  of  fossiliferoua  strata  into  metamorphic  rocks — Limestone  and 
shale  of  Carrara — Metamorphic  strata  of  older  date  than  the  Cambrian  rocks — 
Others  of  Lower  Silurian  origin — Others  of  the  Jurassic  and  Eocene  periods 
in  the  Alps  of  Switzerland  and  Savoy — Why  scarcely  any  of  the  visible  crys- 
talline strata  are  very  modern — Order  of  succession  in  metamorphic  rocks — 
Uniformity  of  mineral  character — Why  the  metamorphic  strata  are  less  cal- 
careous than  the  fossiliferous. 

ACCORDING  to  the  theory  adopted  in  the  last  chapter,  the  age  of  each 
set  of  metamorphic  strata  is  twofold — they  have  been  deposited  at  one 
period,  they  have  become  crystalline  at  another.  We  can  rarely  hope 
to  define  with  exactness  the  date  of  both  these  periods,  the  fossils  having 
been  destroyed'  by  plutonic  action,  and  the  mineral  characters  being  the 
same,  whatever  the  age.  Superposition  itself  is  an  ambiguous  test,  espe- 
cially when  we  desire  to  determine  the  period  of  crystallization.  Suppose, 
for  example,  we  are  convinced  that  certain  metamorphic  strata  in  the 
Alps,  which  are  covered  by  cretaceous  beds,  are  altered  lias ;  this  lias 
may  have  assumed  its  crystalline  texture  in  the  cretaceous  or  in  some 
tertiary  period,  the  Eocene  for  example.  If  in  the  latter,  it  should  be 
called  Eocene  when  regarded  as  a  metamorphic  rock,  although  it  be 
liassic  when  considered  in  reference  to  the  era  of  its  deposition.  Accord- 
ing to  this  view,  the  superposition  of  chalk  does  not  prevent  the  subjacent 
metamorphic  rock  from  being  Eocene. 

When  discussing  the  ages  of  the  plutonic  rocks,  we  have  seen  that 
examples  occur  of  various  primary,  secondary,  and  tertiary  deposits 
converted  into  metamorphic  strata,  near  their  contact  with  granite. 
There  can  be  no  doubt,  in  these  cases,  that  strata,  once  composed  of  mud, 
sand,  and  gravel,  or  of  clay,  marl,  and  shelly  limestone,  have  for  the 
distance  of  several  yards,  and  in  some  instances  several  hundred  feet, 
been  turned  into  gneiss,  mica-schist,  hornblende-schist,  chlorite-sohist, 
quartz  rock,  statuary  marble,  and  the  rest.  (See  the  two  preceding 
Chapters.) 

But  when  the  metamorphic  action  has  operated  on  a  grander  scale, 
it  tends  entirely  to  destroy  all  monuments  of  the  date  of  its  develop- 
ment. It  may  be  easy  to  prove  the  identity  of  two  different  parts  of 
the  same  stratum ;  one,  where  the  rock  has  been  in  contact  with  a  vol- 
canic or  plutonic  mass,  and  has  been  changed  into  marble  or  fc~- 


C12  AGE  OF  METAMOBPHIC  EOCKS  [Cn.  XXXVil 

schist,  and  another  not  far  distant,  where  the  same  bed  remains  unaltered 
and  fossiliferous  ;  but  when  we  have  to  compare  two  portions  of  a  moun- 
tain chain — the  one  metamorphic,  and  the  other  unaltered — all  the  labor 
and  skill  of  the  most  practised  observers  are  required,  and  may  sometimes 
be  at  fault.  I  shall  mention  one  or  two  examples  of  alteration  on  a  grand 
scale,  in  order  to  explain  to  the  student  the  kind  of  reasoning  by  which 
we  are  led  to  infer  that  dense  masses  of  fossiliferous  strata  have  been  con- 
verted into  crystalline  rock. 

Northern  Appenines  —  Carrara. — The  celebrated  marble  of  Carrara, 
used  in  sculpture,  was  once  regarded  as  a  type  of  primitive  limestone. 
It  abounds  in  the  mountains  of  Massa  Carrara,  or  the  "  Apuan  Alps," 
as  they  have  been  called,  the  highest  peaks  of  which  are  nearly  6000 
feet  high.  Its  great  antiquity  was  inferred  from  its  mineral  texture, 
from  the  absence  of  fossils,  and  its  passage  downward  into  talc-schist 
and  garnetiferous  mica-schist ;  these  rocks  again  graduating  downwards 
into  gneiss,  which  is  penetrated,  at  Forno,  by  granite  veins.  Now  the 
researches  of  MM.  Savi,  Boue",  Pareto,  Guidoni,  De  la  Beche,  Hoffmann, 
and  Pilla,  have  demonstrated  that  this  marble,  once  supposed  to  be 
formed  before  the  existence  of  organic  beings,  is,  in  fact,  an  altered 
limestone  of  the  Oolitic  period,  and  the  underlying  crystalline  schists 
are  secondary  sandstones  and  shales,  modified  by  plutonic  action.  In 
order  to  establish  these  conclusions  it  was  first  pointed  out,  that  the  cal- 
careous rocks  bordering  the  Gulf  of  Spezia,  and  abounding  in  Oolitic 
fossils,  assume  a  texture  like  that  of  Carrara  marble,  in  proportion  as 
they  are  more  and  more  invaded  by  certain  trappean  and  plutonic  rocks, 
such  as  diorite,  euphotide,  serpentine,  and  granite,  occurring  in  the  same 
country. 

•  It  was  then  observed  that,  in  places  where  the  secondary  formations 
are  unaltered,  the  uppermost  consist  of  common  Apennine  limestone 
with  nodules  of  flint,  below  which  are  shales,  and  at  the  base  of  all,  ar- 
gillaceous and  siliceous  sandstones.  In  the  limestone,  fossils  are  frequent, 
but  very  rare  in  the  underlying  shale  and  sandstone.  Then  a  gradation 
was  traced  laterally  from  those  rocks  into  another  and  corresponding 
series,  which  is  completely  metamorphic ;  for  at  the  top  of  this  we  find 
a  white  granular  marble,  wholly  devoid  of  fossils,  and  almost  without 
stratification,  in  which  there  are  no  nodules  of  flint,  but  in  its  place 
siliceous  matter  disseminated  through  the  mass  in  the  form  of  prisms  of 
quartz.  Below  this,  and  in  place  of  the  shales,  are  talc-schists,  jasper, 
and  hornstone ;  and  at  the  bottom,  instead  of  the  siliceous  and  argilla- 
ceous sandstones,  are  quartzite  and  gneiss.*  Had  these  secondary  strata 
of  the  Apennines  undergone  universally  as  great  an  amount  of  transmu- 
tation, it  would  have  been  impossible  to  form  a  conjecture  respecting 
their  true  age ;  and  then,  according  to  the  method  of  classification 
adopted  by  the  earlier  geologists,  they  would  have  ranked  as  primary 

*  See  notices  of  Savi,  Hoffmann,  and  others,  referred  to  by  Boue,  Bull,  de  la 
Soc.  Geol.  de  France,  torn.  v.  p.  317;  and  torn,  iii.  p.  xliv ;  also  Pilla,  cited  by 
Murcbison,  Quart.  Geol.  Journ.  vol.  v.  p.  266. 


Cu.  XXXVII]  OF  THE   SWISS  ALPS.  613 

rocks.  In  that  case  the  date  of  their  origin  would  have  been  thrown  back 
to  an  area  antecedent  to  .the  deposition  of  the  Lower  Silurian  or  Cam- 
brian strata,  although  in  reality  they  were  formed  in  the  Oolitic  period, 
and  altered  at  some  subsequent  and  perhaps  much  later  epoch. 

Alps  of  Switzerland. — In  the  Alps,  analogous  conclusions  have  been 
drawn  respecting  the  alteration  of  strata  on  a  still  more  extended  scale. 
In  the  eastern  part  of  that  chain,  some  of  the  primary  fossiliferous  strata, 
as  well  as  the  older  secondary  formations,  together  with  the  oolitic  and 
cretaceous  rocks,  are  distinctly  recognizable.  Tertiary  deposits  also 
appear  in  a  less  elevated  position  on  the  flanks  of  the  Eastern  Alps ;  but 
in  the  Central  or  Swiss  Alps,  the  primary  fossiliferous  and  older  second- 
ary formations  disappear,  and  the  Cretaceous,  Oolitic,  Liassic,  and  at 
some  points  even  the  Eocene  strata,  graduate  insensibly  into  metamor- 
phic  rocks,  consisting  of  granular  limestone,  talc-schist,  talcose-gneiss, 
micaceous  schist,  and  other  varieties.  In  regard  to  the  age  of  this  vast 
assemblage  of  crystalline  strata,  we  can  merely  affirm  that  some  of  the 
upper  portions  are  altered  newer  secondary,  and  some  of  them  even 
Eocene  deposits ;  but  we  cannot  avoid  suspecting  that  the  disappearance 
both  of  the  older  secondary  and  primary  fossiliferous  rocks  may  be 
owing  to  their  having  been  all  converted  in  the  same  region  into  crystal- 
line schist 

It  is  difficult  to  convey  to  those  who  have  never  visited  the  Alps  a 
just  idea  of  the  various  proofs  which  concur  to  produce  this  conviction. 
In  the  first  place,  there  are  certain  regions  where  Oolitic,  Cretaceous, 
and  Eocene  strata  have  been  turned  into  granular  marble,  gneiss,  and 
other  metamorphic  schists,  near  their  contact  with  granite.  This  fact 
shows  undeniably  that  plutonic  causes  continued  to  be  in  operation  in  the 
Alps  down  to  a  late  period,  even  after  the  deposition  of  some  of  the  num- 
mulitie  or  middle  Eocene  formations.  Having  established  this  point, 
we  are  the  more  willing  to  believe  that  many  inferior  fossiliferous  rocks, 
probably  exposed  for  longer  periods  to  a  similar  action,  may  have  become 
metamorphic  to  a  still  greater  extent. 

We  also  discover  in  parts  of  the  Swiss  Alps  dense  masses  of  second- 
ary and  even  tertiary  strata,  which  have  assumed  that  semi-crystalline 
texture  which  Werner  called  transition,  and  which  naturally  led  his  fol- 
lowers, who  attached  great  importance  to  mineral  characters  taken  alone, 
to  class  them  as  transition  formations,  or  as  groups  older  than  the  lowest 
secondary  rocks.  (See  p.  93.)  Now,  it  is  probable  that  these  strata 
have  been  affected,  although  in  a  less  intense  degree,  by  that  same  plu- 
tonic action  which  has  entirely  altered  and  rendered  metamorphic  so 
many  of  the  subjacent  formations ;  for  in  the  Alps,  this  action  has  by 
no  means  been  confined  to  the  immediate  vicinity  of  granite.  Granite,  in- 
deed, and  other  plutonic  rocks,  rarely  make  their  appearance  at  the  sur- 
face, notwithstanding  the  deep  ravines  which  lay  open  to  view  the 
internal  structure  of  these  mountains.  That  they  exist  below  at  no 
great  depth  we  cannot  doubt,  and  we  have  already  seen  (p.  569)  that  at 
some  points,  as  in  the  Valorsine,  near  Mont  Blanc,  granite  and  granitic 


614:  AGE   OF  METAMOKPHIC  ROCKS.          [Cn.  XXXVII 

veins  are  observable,  piercing  through  talcose  gneiss,  which  passes  insen- 
sibly upwards  into  secondary  strata. 

It  is  certainly  in  the  Alps  of  Switzerland  and  Savoy,  more  than  in 
any  other  district  in  Europe,  that  the  geologist  is  prepared  to  meet  with 
the  signs  of  an  intense  development  of  plutonic  action ;  for  here  we  find 
the  most  stupendous  monuments  of  mechanical  violence,  by  which  strata 
thousands  of  feet  thick  have  been  bent,  folded,  and  overturned.  (See 
p.  58.)  It  is  here  that  marine  secondary  formations  of  a  comparatively 
modern  date,  such  as  the  Oolitic  and  Cretaceous,  have  been  upheaved 
to  the  height  of  12,000,  and  some  Eocene  strata  to  elevations  of  10,000 
feet  above  the  level  of  the  sea ;  and  even  deposits  of  the  Miocene  era 
have  been  raised  4000  or  5000  feet,  so  as  to  rival  in  height  the  loftiest 
mountains  in  Great  Britain. 

If  the  reader  will  consult  the  works  of  many  eminent  geologists  who 
have  explored  the  Alps,  especially  those  of  MM.  De  Beaumont,  Studer, 
Necker,  Boue,  and  Murchison,  he  will  learn  that  they  all  share,  more 
or  less  fully,  in  the  opinions  above  expressed.  It  has,  indeed,  been 
stated  by  MM.  Studer  and  Hugi,  that  there  are  complete  alternations 
on  a  large  scale  of  secondary  strata,  containing  fossils,  with  gneiss  and 
other  rocks,  of  a  perfectly  metamorphic  structure.  I  have  visited  some 
of  the  most  remarkable  localities  referred  to  by  these  authors ;  but  al- 
though agreeing  with  them  that  there  are  passages  from  the  fossiliferous  . 
to  the  metamorphic  series  far  from  the  contact  of  granite  or  other  plu- 
tonic rocks,  I  was  unable  to  convince  myself  that  the  distinct  alterna- 
tions of  highly  crystalline,  with  unaltered  strata  above  alluded  to,  might 
not  admit  of  a  different  explanation.  In  one  of  the  sections  described 
by  M.  Studer  in  the  highest  of  the  Bernese  Alps,  namely  in  the  Roth- 
thai,  a  valley  bordering  the  line  of  perpetual  snow  on  the  northern  side 
of  the  Jungfrau,  there  occurs  a  mass  of  gneiss  1000  feet  thick,  and 
15,000  feet  long,  which  I  examined,  not  only  resting  upon,  but  also 
again  covered  by  strata  containing  oolitic  fossils.  These  anomalous  ap 
pearances  may  partly  be  explained  by  supposing  great  solid  wedges  of 
intrusive  gneiss  to  have  been  forced  in  laterally  between  strata  to  which 
I  found  them  to  be  in  many  sections  unconformable.  The  superposi 
tion,  also,  of  the  gneiss  to  the  oolite  may,  in  some  cases,  be  due  to  a 
reversal  of  the  original  position  of  the  beds  in  a  region  where  the  con- 
vulsions have  been  on  so  stupendous  a  scale. 

On  the  Sattel  also,  at  the  base  of  the  Gestellihorn,  above  Enzen,  in 
the  valley  of  Urbach,  near  Meyringen,  some  of  the  intercalations  of 
gneiss  between  fossiliferous  strata  may,  I  conceive,  be  ascribed  to  me- 
chanical derangement.  Almost  any  hypothesis  of  repeated  changes  of 
position  may  be  resorted  to  in  a  region  of  such  extraordinary  confusion. 
The  secondary  strata  may  first  have  been  vertical,  and  then  certain  por- 
tions may  have  become  metamorphic  (the  plutonic  influence  ascending 
from  below),  while  intervening  strata  remained  unchanged.  The  whole 
series  of  beds  may  then  again  have  been  thrown  into  a  nearly  horizontal 


CH.  XXXVIL]  ORDER  OF  SUCCESSION".  615 

position,  giving  rise  to  the  superposition  of  crystalline  upon  fossiliferous 
formations. 

It  was  remarked,  in  Chap.  XXXTY.,  that  as  the  hypogene  rocks,  both 
stratified  and  unstratified,  crystallize  originally  at  a  certain  depth  beneath 
the  surface,  they  must  always,  before  they  are  upraised  and  exposed  at 
the  surface,  be  of  considerable  antiquity,  relatively  to  a  large  portion  of 
the  fossiliferous  and  volcanic  rocks.  They  may  be  fonning  at  all  periods ; 
but  before  any  of  them  can  become  visible,  they  must  be  raised  above  the 
level  of  the  sea,  and  some  of  the  rocks  which  previously  concealed  them 
must  have  been  removed  by  denudation. 

In  Canada  the  fossiliferous  beds  of  the  Cambrian  format'on  repose  un- 
conformably  on  gneiss,  which  was  evidently  crystalline  befcre  the  deposi- 
tion of  the  Cambrian  (or  Potsdam)  sandstone.  In  Anglesea,  as  was 
before  remarked,  the  metamorphism  of  the  schists,  according  to  the 
observations  of  Professor  Ramsay,  took  place  during  the  Lower  Silurian 
period.  Coupling  these  conclusions  with  the  fact  that  a  hypogene  tex- 
ture has  been  superinduced  in  the  Alps  on  Middle  Eocene  deposits  (see 
p.  600),  we  cannot  doubt  that,  hereafter,  geologists  will  succeed  in  de- 
tecting crystalline  schists  of  almost  every  age  in  the  chronological  series, 
although  the  quantity  of  metamorphic  rocks  visible  at  the  surface  must, 
for  reasons  above  explained,  diminish  rapidly  in  proportion  as  the  monu- 
ments of  newer  eras  are  investigated. 

Order  of  succession  in  metamorphic  rocks. — There  is  no  universal  and 
invariable  order  of  superposition  in  metamorphic  rocks,  although  a  par- 
ticular arrangement  may  prevail  throughout  countries  of  great  extent, 
for  the  same  reason  that  it  is  traceable  in  those  sedimentary  formations 
from  which  crystalline  strata  are  derived.  Thus,  for  example,  we  have 
seen  that  in  the  Apennines,  near  Carrara,  the  descending  series,  where 
it  is  metamorphic,  consists  of,  1st,  saccharine  marble;  2dly,  talcos> 
schist;  and  3dly,  of  quartz-rock  and  gneiss;  where  unaltered,  of,  1st, 
fossiliferous  limestone ;  2dly,  shale ;  and  3dly,  sandstone.  , 

But  if  we  investigate  different  mountain  chains,  we  find  gneiss,  mica- 
schist,  hornblende-schist,  chlorite-schist,  hypogene  limestone,  and  other 
rocks,  succeeding  each  other,  and  alternating  with  each  other,  in  every 
possible  order.  It  is,  indeed,  more  common  to  meet  with  some  variety 
of  clay-slate  forming  the  uppermost  member  of  a  metamorphic  series 
than  any  other  rock ;  but  this  fact  by  no  means  implies,  as  some  have 
imagined,  that  all  clay-slates  were  formed  at  the  close  of  an  imaginary 
period,  when  the  deposition  of  the  crystalline  strata  gave  way  to  that 
of  ordinary  sedimentary  deposits.  Such  clay-slates,  in  fact,  are  variable 
in  composition,  and  sometimes  alternate  with  fossiliferous  strata,  so  that 
they  may  be  said  to  belong  almost  equally  to  the  sedimentary  and  meta- 
morphic order  of  rocks.  It  is  probable  that  had  they  been  subjected  to 
more  intense  plutonic  action,  they  would  have  been  transformed  into 
hornblende- schist,  foliated  chlorite-schist,  scaly  talcose-schist,  mica-schist, 
or  other  more  perfectly  crystalline  rocks,  such  as  are  usually  associated 
with  gneiss. 


616       SCARCITY  OF  LIME  IN  METAMORPHIC  KOCKS.     [OH.  XXX Ylf, 

Uniformity  of  mineral  character  in  Hypogene  rocks.  —  Humboldt 
has  emphatically  remarked,  that  when  we  pass  to  another  hemisphere, 
we  see  new  forms  of  animals  and  plants,  and  even  new  constellations  in 
the  heavens ;  but  in  the  rocks  we  still  recognize  our  old  acquaintances, 
— the  same  granite,  the  same  gneiss,  the  same  micaceous  schist,  quartz- 
rock,  and  the  rest.  It  is  certainly  true  that  there  is  a  great  and  striking 
general  resemblance  in  the  principal  kinds  of  hypogene  rocks,  although 
of  very  different  ages  and  countries ;  but  it  has  been  shown  that  each 
of  these  are,  in  fact,  geological  families  of  rocks,  and  not  definite  mineral 
compounds.  They  are  much  more  uniform  in  aspect  than  sedimentary 
strata,  because  these  last  are  often  composed  of  fragments  varying  greatly 
in  form,  size,  and  colour,  and  contain  fossils  of  different  shapes  and  min- 
eral composition,  and  acquire  a  variety  of  tints  from  the  mixture  of 
various  kinds  of  sediment.  The  materials  of  such  strata,  if  melted  and 
made  to  crystallize,  would  be  subject  to  chemical  laws,  simple  and  uni- 
form in  their  action,  the  same  in  every  climate,  and  wholly  undisturbed 
by  mechanical  and  organic  causes. 

Nevertheless,  it  would  be  a  great  error  to  assume  that  the  hypogene 
rocks,  considered  as  aggregates  of  simple  minerals,  are  really  more  homo- 
geneous in  their  composition  than  the  several  members  of  the  sediment- 
ary series.  In  the  first  place,  different  assemblages  of  hypogene  rocks 
occur  in  different  countries ;  and,  secondly,  in  any  one  district,  the  rocks 
which  pass  under  the  same  name  are  often  extremely  variable  in  their 
component  ingredients,  or  at  least  in  the  proportions  in  which  each  of 
these  are  present.  Thus,  for  example,  gneiss  and  mica-schist,  so  abun- 
dant in  the  Grampians,  are  wanting  in  Cumberland,  Wales,  and  Corn- 
wall ;  in  parts  of  the  Swiss  and  Italian  Alps,  the  gneiss  and  granite  are 
talcose,  and  not  micaceous,  as  in  Scotland ;  hornblende  prevails  in  the 
granite  of  Scotland — schorl  in  that  of  Cornwall — albite  in  the  plutonic 
rocks  of  the  Andes — common  felspar  in  those  of  Europe.  In  one  part 
of  Scotland,  the  mica-schist  is  full  of  garnets ;  in  another  it  is  wholly 
devoid  of  them :  while  in  South  America,  according  to  Mr.  Darwin,  it 
is  the  gneiss,  and  not  the  mica-schist,  which  is  most  commonly  garnetif- 
erous.  And  not  only  do  the  proportional  quantities  of  felspar,  quartz, 
mica,  hornblende,  and  other  minerals,  vary  in  hypogene  rocks  bearing 
the  same  name ;  but  what  is  still  more  important,  the  ingredients,  as 
we  have  seen,  of  the  same  simple  mineral  are  not  always  constant, 
(p.  463  and  table,  p.  104). 

The  metamorphic  strata,  why  less  calcareous  than  the  fossiliferous. — 
It  has  been  remarked,  that  the  quantity  of  calcareous  matter  in  meta- 
morphic  strata,  or,  indeed,  in  the  hypogene  formations  generally,  is  far 
less  than  in  fossiliferous  deposits.  Thus  the  crystalline  schists  of  the 
Grampians  in  Scotland,  consisting  of  gneiss,  mica-schist,  hornblende 
schist,  and  other  rocks,  many  thousands  of  yards  in  thickness,  contain 
•in  exceedingly  small  proportion  of  interstratified  calcareous  beds,  al- 
though these  have  been  the  objects  of  careful  search  for  economical 
purposes.  Yet  limestone  is  not  wanting  in  the  Grampians,  and  it  is 


CH.  XXXVIL]    SCARCITY  OF  LIME  IN  METAMORPHIC  ROCKS.       617 

associated  sometimes  with  gneiss,  sometimes  with  mica-schist,  and  in 
other  places  with  other  members  of  the  metamorphic  series.  But  where 
limestone  occurs  abundantly,  as  at  Carrara,  and  in  parts  of  the  Alps,  in 
connection  with  hypogene  rocks,  it  usually  forms  one  of  the  superior 
members  of  the  crystalline  group. 

The  scarcity,  then,  of  carbonate  of  lime  in  the  plutonic  and  meta- 
morphic rocks  generally,  seems  to  be  the  result  of  some  general  cause. 
So  long  as  the  hypogene  rocks  were  believed  to  have  originated  antece- 
dently to  the  creation  of  organic  beings,  it  was  easy  to  impute  the 
absence  of  lime  to  the  non-existence  of  those  mollusca  and  zoophytes  by 
which  shells  and  corals  are  secreted ;  but  when  we  ascribe  the  crystalline 
formations  to  plutonic  action,  it  is  natural  to  inquire  whether  this  action 
itself  may  not  tend  to  expel  carbonic  acid  and  lime  from  the  materials 
which  it  reduces  to  fusion  or  semi-fusion.  Although  we  cannot  descend 
into  the  subterranean  regions  where  volcanic  heat  is  developed,  we  can 
observe  in  regions  of  spent  volcanos,  such  as  Auvergne  and  Tuscany, 
hundreds  of  springs,  both  cold  and  thermal,  flowing  out  from  granite 
and  other  rocks,  and  having  their  waters  plentifully  charged  with  carbo- 
nate of  lime.  The  quantity  of  calcareous  matter  which  these  springs 
transfer,  in  the  course  of  ages,  from  the  lower  parts  of  the  earth's  crust 
to  the  superior  or  newly  formed  parts  of  the  same,  must  be  considerable.* 

If  the  quantity  of  siliceous  and  aluminous  ingredients  brought  up  by 
such  springs  were  great,  instead  of  being  utterly  insignificant,  it  might 
be  contended  that  the  mineral  matter  thus  expelled  implies  simply  the 
decomposition  of  ordinary  subterranean  rocks ;  but  the  prodigious  excess 
of  carbonate  of  lime  over  every  other  element  must,  in  the  course  of 
time,  cause  the  crust  of  the  earth  below  to  be  almost  entirely  deprived  of 
its  calcareous  constituents,  while  we  know  that  the  same  action  imparts 
to  newer  deposits,  ever  forming  in  seas  and  lakes,  an  excess  of  carbonate 
of  lime.  Calcareous  matter  is  poured  into  these  lakes,  and  the  ocean, 
by  a  thousand  springs  and  rivers ;  so  that  part  of  almost  every  new  cal- 
careous rock  chemically  precipitated,  and  of  many  reefs  of  shelly  and 
coralline  stone,  must  be  derived  from  mineral  matter  subtracted  by  plu- 
tonic agency,  and  driven  up  by  gas  and  steam  from  fused  and  heated 
rocks  in  the  bowels  of  the  earth. 

Not  only  carbonate  of  lime,  but  also  free  carbonic  acid  gas  is  given 
off  plentifully  from  the  soil  and  crevices  of  rocks  in  regions  of  active 
and  spent  volcanos,  as  near  Naples,  and  in  Auvergne.  By  this  process, 
fossil  shells  or  corals  may  often  lose  their  carbonic  acid,  and  the  resi- 
dual lime  may  enter  into  the  composition  of  augite,  hornblende,  garnet, 
and  other  hypogene  minerals.  That  the  removal  of  the  calcareous  mat- 
ter of  fossil  shells  is  of  frequent  occurrence,  is  proved  by  the  fact  of  such 
organic  remains  being  often  replaced  by  silex  or  other  minerals,  and 
sometimes  by  the  space  once  occupied  by  the  fossil  being  left  empty,  or 
only  marked  by  a  faint  impression.  We  ought  not  indeed  to  marvel  at 
the  general  absence  of  organic  remains  from  the  crystalline  strata,  when 
*  See  Principles,  Index,  "  Calcareous  Springs." 


618  MINERAL  VEINS.  [On.  XXXVIII. 

we  bear  in  mind  how  often  fossils  are  obliterated,  wholly  or  in  part,  even 
in  tertiary  formations — how  often  vast  masses  of  sandstone  and  shale 
of  different  ages,  and  thousands  of  feet  thick,  are  devoid  of  fossils- - 
how  certain  strata  may  first  have  been  deprived  of  a  portion  of  their 
fossils  when  they  became  semi-crystalline,  or  assumed  the  transition  state 
of  Werner — and  how  the  remaining  portion  may  have  been  effaced 
when  they  were  rendered  nietamorphic.  Rocks  of  the  last-mentioned 
class,  moreover,  must  have  sometimes  been  exposed  again  and  again  to 
renewed  plutonic  action. 


CHAPTER  XXXVIII. 

MINERAL    VEINS. 

Werner's  doctrine  that  mineral  veins  were  fissures  filled  from  above — Veins  of 
segregation — Ordinary  metalliferous  veins  or  lodes — Their  frequent  coincidence 
with  faults — Proofs  that  they  originated  in  fissures  in  solid  rock — Veins  shifting 
other  veins — Polishing  of  their  walls  or  "  slicken-sides" — Shells  and  pebbles  in 
lodes — Evidence  of  the  successive  enlargement  and  reopening  of  veins — Four- 
net's  observations  in  Auvergne — Dimensions  of  veins — Why  some  alternately 
swell  out  and  contract — Filling  of  lodes  by  sublimation  from  below — Chemical 
and  electrical  action — Relative  age  of  the  precious  metals — Copper  and  lead 
veins  in  Ireland  older  than  Cornish  tin — Lead  vein  in  lias,  Glamorganshire — 
Gold  in  Russia,  California,  and  Australia — Connection  of  hot  springs  and  min- 
eral veins — Concluding  remarks. 

THE  manner  in  which  metallic  substances  are  distributed  through  the 
earth's  crust,  and  more  especially  the  phenomena  of  those  nearly  verti- 
cal and  tabular  masses  of  ore  called  mineral  veins,  from  which  the  larger 
part  of  the  precious  metals  used  by  man  are  obtained, — these  are  sub- 
jects of  the  highest  practical  importance  to  the  miner,  and  of  no  less 
theoretical  interest  to  the  geologist. 

The  views  entertained  respecting  metalliferous  veins  have  been  modi- 
fied, or  rather,  have  undergone  an  almost  complete  revolution,  since  the 
middle  of  the  last  century,  when  Werner,  as  director  of  the  School  of 
Mines,  at  Freiburg  in  Saxony,  first  attempted  to  generalize  the  facts  then 
known.  He  taught  that  mineral  veins  had  originally  been  open  fissures 
which  were  gradually  filled  up  with  crystalline  and  metallic  matter,  and 
that  many  of  them,  after  being  once  filled,  had  been  again  enlarged  or 
reopened.  He  also  pointed  out  that  veins  thus  formed  are  not  all  refera- 
ble to  one  era,  but  are  of  various  geological  dates. 

Such  opinions,  although  slightly  hinted  at  by  earlier  writers,  had  never 
before  been  generally  received,  and  their  announcement  by  one  of  high 
authority  and  great  experience  constituted  an  era  in  the  science.  Never- 
theless, I  have  shown,  when  tracing  in  another  work,  the  history  and 
progress  of  geology,  that  Werner  was  far  behind  some  of  his  predeces- 
sors in  his  theory  of  the  volcanic  rocks,  and  less  enlightened  than  his 


CH.  XXXYIIL]     DIFFERENT  KINDS  OF  MINERAL   VEINS.  619 

contemporary,  Dr.  Hutton,  in  his  speculations  as  to  the  origin  of  granite.* 
According  to  him,  the  plutonic  formations,  as  well  as  the  crystalline 
schists,  were  substances  precipitated  from  a  chaotic  fluid  in  some  prime- 
val or  nascent  condition  of  the  planet;  and  the  metals,  therefore,  being 
closely  connected  with  them,  had  partaken,  according  to  him,  of  a  like 
mysterious  origin.  He  also  held  that  the  trap  rocks  were  aqueous  de- 
posits, and  that  dikes  of  porphyry,  greenstone,  and  basalt,  were  fissures 
filled  with  their  several  contents  from  above.  Hence  he  naturally  infer- 
red that  mineral  veins  had  derived  their  component  materials  from  an 
incumbent  ocean,  rather  than  from  a  subterranean  source ;  that  these 
materials  had  been  first  dissolved  in  the  waters  above,  instead  of  having 
risen  up  by  sublimation  from  lakes  and  seas  of  igneous  matter  below. 

In  proportion  as  the  hypothesis  of  a  primeval  fluid,  or  "  chaotic  men- 
struum," was  abandoned,  in  reference  to  the  plutonic  formations,  and 
when  all  geologists  had  come  to  be  of  one  mind  as  to  the  true  relation 
of  the  volcanic  and  trappean  rocks,  reasonable  hopes  began  to  be  enter- 
tained that  the  phenomena  of  mineral  veins  might  be  explained  by  known 
causes,  or  by  chemical,  thermal,  and  electrical  agency  still  at  work  in 
the  interior  of  the  earth.  The  grounds  of  this  conclusion  will  be  better 
understood  when  the  geological  facts  brought  to  light  by  mining  opera- 
tions have  been  described  and  explained. 

On  different  kinds  of  mineral  veins.  —  Every  geologist  is  familiarly 
acquainted  with  those  veins  of  quartz  which  abound  in  hypogene  strata, 
forming  lenticular  masses  of  limited  extent.  They  are  sometimes  ob- 
served, also,  in  sandstones  and  shales.  Veins  of  carbonate  of  lime  are 
equally  common  in  fossiliferous  rocks,  especially  in  limestones.  Such 
veins  appear  to  have  once  been  chinks  or  small  cavities,  caused,  like 
cracks  in  clay,  by  the  shrinking  of  the  mass,  which  has  consolidated 
from  a  fluid  state,  or  has  simply  contracted  its  dimensions  in  passing 
from  a  higher  to  a  lower  temperature.  Siliceous,  calcareous,  and  occa- 
sionally metallic  matters,  have  sometimes  found  their  way  simultaneously 
into  such  empty  spaces,  by  infiltration  from  the  surrounding  rocks,  or 
by  segregation,  as  it  is  often  termed.  Mixed  with  hot  water  and  steam, 
metallic  ores  may  have  permeated  a  pasty  matrix  until  they  reached 
those  receptacles  formed  by  shrinkage,  and  thus  gave  rise  to  that  irregu- 
lar assemblage  of  veins,  called  by  the  Germans  a  "  stockwerk,"  in  allu- 
sion to  the  different  floors  on  which  the  mining  operations  are  in  such 
cases  carried  on. 

The  more  ordinary  or  regular  veins  are  usually  worked  in  vertical 
shafts,  and  have  evidently  been  fissures  produced  by  mechanical  violence. 
They,  traverse  all  kinds  of  rocks,  both  hypogene  and  fossiliferous,  and 
extend  downwards  to  indefinite  or  unknown  depths.  We  may  assume 
that  they  correspond  with  such  rents  as  we  see  caused  from  time  to  time 
by  the  shock  of  an  earthquake.  Metalliferous  veins,  referable  to  such 
agency,  are  occasionally  a  few  inches  wide,  but  more  commonly  3  or  4 

*  Principles,  &c..  chap.  iv. 


620 


ORIGIN  OF  METALLIFEROUS  VEINS.      [Cn.  XXXVIIL 


feet.  They  hold  their  course  continuously  in  a  certain  prevailing  direc- 
tion for  miles  or  leagues,  passing  through  rocks  varying  in  mineral  com- 
position. 

That  metalliferous  veins  were  fissures.  —  As  some  intelligent  miners, 
after  an  attentive  study  of  metalliferous  veins,  have  been  unable  to  re- 
concile many  of  their  characteristics  with  the  hypothesis  of  fissures,  I 
j?ig.  7io.  shall  begin  by  stating  the 

evidence  in  its  favour.  The 
most  striking  fact  perhaps 
which  can  be  adduced  in  its 
support  is,  the  coincidence 
of  a  considerable  proportion 
of  mineral  veins  with  faults, 
or  those  dislocations  of  rocks 
which  are  indisputably  due 
to  mechanical  force,  as  above 
explained  (p.  61).  There 
are  even  proofs  in  almost 
every  mining  district  of  a 
succession  of  faults,  by 
which  the  opposite  walls  of 
rents,  now  the  receptacles 
of  metallic  substances,  have 
suffered  displacement.  Thus, 
for  example,  suppose  a  a, 
fig.  710,  to  be  a  tin  lode  in 
Cornwall,  the  term  lode  be- 
ing applied  to  veins  contain- 
ing metallic  ores.  This 
lode,  running  east  and  west, 
is  a  yard  wide,  and  is  shift- 
ed by  a  copper  lode  (b  &), 
of  similar  width. 

The  first  fissure  (a  a)  has 
been  filled  with  various  ma- 
terials, partly  of  chemical 
origin,  such  as  quartz,  fluor- 
spar, peroxide  of  tin,  sul- 
phuret  of  copper,  arsenical 
pyrites,  bismuth,  and  sul- 
phuret  of  nickel,  and  partly  of  mechanical  origin,  comprising  clay  and 
angular  fragments  or  detritus  of  the  intersected  rocks.  The  plates  of 
quartz  and  the  ores  are,  in  some  places,  parallel  to  the  vertical  sides  or 
walls  of  the  vein,  being  divided  from  each  other  by  alternating  layers 
of  clay,  or  other  earthy  matter.  Occasionally  the  metallic  ores  are  dis- 
seminated'in  detached  masses  among  the  vein-stones. 


Vertical  sections  of  the  mine  of  Huel  Peever,  Redruth, 
Cornwall. 


CH.  XXXVIII.]      ORIGIN  OF  METALLIFEROUS  VEINS.  621 

It  is  clear  that,  after  the  gradual  introduction  of  the  tin  and  other 
substances,  the  second  rent  (b  1)  was  produced  by  another  fracture  ac- 
companied by  a  displacement  of  the  rocks  along  the  plane  of  b  b.  This 
new  opening  was  then  filled  with  minerals,  some  of  them  resembling 
those  in  a  a,  as  fluor-spar  (or  fluate  of  lime)  and  quartz ;  others  diffe- 
rent, the  copper  being  plentiful  and  the  tin  wanting  or  very  scarce. 

We  must  next  suppose  the  shock  of  a  third  earthquake  to  occur, 
breaking  asunder  all  the  rocks  along  the  line  c  c,  fig.  711;  the  fissure  in 
this  instance,  being  only  6  inches  wide,  and  simply  filled  with  clay,  de- 
rived, probably,  from  the  friction  of  the  walls  of  the  rent,  or  partly, 
perhaps,  washed  in  from  above.  This  new  movement  has  heaved  the 
rock  in  such  a  manner  as  to  interrupt  the  continuity  of  the  copper  vein 
(b  b)}  and,  at  the  same  time,  to  shift  or  heave  laterally  in  the  same  di- 
rection a  portion  of  the  tin  vein  which  had  not  previously  been  broken. 

Again,  in  fig.  712  we  see  evidence  of  a  fourth  fissure  (d  d),  also  filled 
with  clay,  which  has  cut  through  the  tin  vein  (a  a),  and  has  lifted  it 
slightly  upwards  towards  the  south.  The  various  changes  here  repre- 
sented are  not  ideal,  but  are  exhibited  in  a  section  obtained  in  working 
an  old  Cornish  mine,  long  since  abandoned,  in  the  parish  of  .Redruth, 
called  Huel  Peever,  and  described  both  by  Mr.  Williams  and  Mr. 
Carne.*  The  principal  movement  here  referred  to,  or  that  of  c  c,  fig. 
712,  extends  through  a  space  of  no  less  than  84  feet ;  but  in  this,  as  in 
the  case  of  the  other  three,  it  will  be  seen  that  the  outline  of  the  country 
above,  rf,  c,  £,  a,  &c.,  or  the  geographical  features  of  Cornwall,  are  not 
affected  by  any  of  the  dislocations,  a  powerful  denuding  force  having 
clearly  been  exerted  subsequently  to  all  the  faults.  (See  above,  p.  69.) 
It  is  commonly  said  in  Cornwall,  that  there  are  eight  distinct  systems  of 
veins  which  can  in  like  manner  be  referred  to  as  many  successive  move- 
ments or  fractures ;  and  the  German  miners  of  the  Hartz  Mountains  speak 
also  of  eight  systems  of  veins,  referable  to  as  many  periods. 

Besides  the  proofs  of  mechanical  action  already  explained,  the  opposite 
walls  of  veins  are  often  beautifully  polished,  as  if  glazed,  and  are  not 
imfrequently  striated,  or  scored  with  parallel  furrows  and  ridges,  such  as 
would  be  produced  by  the  continued  rubbing  together  of  surfaces  of  un- 
equal hardness.  These  smoothed  surfaces  resemble  the  rocky  floor  over 
which  a  glacier  has  passed  (see  fig.  p.  127).  They  are  common  even  in 
cases  wnere  there  has  been  no  shift,  and  occur  equally  in  non-metalliferous 
fissures.  They  are  called  by  miners  "  slicken-sides,"  from  the  German 
scklichten,  to  plane,  and  seite,  side.  It  is  supposed  that  the  lines  of  the 
stria?  indicate  the  direction  in  which  the  rocks  were  moved.  During  one 
of  the  minor  earthquakes  in  Chili,  which  happened  about  the  year  1840? 
and  was  described  to  me  by  an  eye-witness,  the  brick  walls  of  a  building 
were  rent  vertically  in  several  places,  and  made  to  vibrate  for  several 
minutes  during  each  shock,  after  which  they  remained  uninjured,  and 
without  any  opening,  although  the  line  of  each  crack  was  still  visible. 

*  GeoL  Trans.  voL  iv.  p.  139 ;  Trans.  Roy.  GeoL  Society,  Cornwall,  vol.  ii.  p.  90. 


622  SUCCESSIVE  ENLAKGEMENTS   OF  VEINS.      [Cn.  XXXVIII. 

When  all  movement  had  ceased,  there  were  seen  on  the  floor  of  the 
house,  at  the  bottom  of  each  rent,  small  heaps  of  fine  brickdust,  evidently 
produced  by  trituration. 

In  some  of  the  veins  in  the  mountain  limestone  of  Derbyshire,  contain- 
ing lead,  the  vein-stuff,  which  is  nearly  compact,  is  occasionally  traversed 
by  what  may  be  called  a  vertical  crack  passing  down  the  middle  of  the 
vein.  The  two  faces  in  contact  are  slicken-sides,  well  polished  and  fluted, 
and  sometimes  covered  by  a  thin  coating  of  lead-ore.  When  one  side  of 
the  vein-stuff  is  removed,  the  other  side  cracks,  especially  if  small  holes 
be  made  in  it,  and  fragments  fly  off  with  loud  explosions,  and  continue  to 
do  so  for  some  days.  The  miner,  availing  himself  of  this  circumstance, 
makes  with  his  pick  small  holes  about  6  inches  apart,  and  4  inches  deep, 
and  on  his  return  in  a  few  hours  finds  every  part  ready  broken  to  his 
hand.*  These  phenomena  and  their  causes  (probably  connected  with 
electrical  action)  seem  scarcely  to  have  attracted  the  notice  which  they 
deserve. 

That  a  great  many  veins  communicated  originally  with  the  surface  of 
the  country  above,  or  with  the  bed  of  the  sea,  is  proved  by  the  occur- 
rence in  *hem  of  well-rounded  pebbles,  agreeing  with  those  in  superficial 
alluviums,  as  in  Auvergne  and  Saxony.  In  Bohemia,  such- pebbles 
have  been  met  with  at  the  depth  of  180  fathoms.  In  Cornwall,  Mr. 
Carne  mentions  true  pebbles  of  quartz  and  slate  in  a  tin  lode  of  the 
Relistran  Mine,  at  the  depth  of  600  feet  below  the  surface.  They  were 
cemented  by  oxide  of  tin  and  bisulphuret  of  copper,  and  were  traced 
over  a  space  more  than  12  feet  long  and  as  many  wide.j-  Marine  fossil 
shells,  also,  have  been  found  at  great  depths,  having  probably  been  en- 
gulfed during  submarine  earthquakes.  Thus,  a  gryphaea  is  stated  by 
M.  Virlet  to  have  been  met  with  in  a  lead-mine  near  Se"mur,  in  France 
and  a  madrepore  in  a  compact  vein  of  cinnabar  in  Hungary  .J 

When  different  sets  or  systems  of  veins  occur  in  the  same  country, 
those  which  are  supposed  to  be  of  contemporaneous  origin,  and  which 
are  filled  with  the  same  kind  of  metals,  often  maintain  a  general  paral- 
lelism of  direction.  Thus,  for  example,  both  the  tin  and  copper  veins 
in  Cornwall  run  nearly  east  and  west,  while  the  lead-veins  run  north 
and  south ;  but  there  is  no  general  law  of  direction  common  to  different 
mining  districts.  The  parallelism  of  the  veins  is  another  reason  for 
regarding  them  as  ordinary  fissures,  for  we  observe  that  contemporaneous 
trap  dikes,  admitted  by  all  to  be  masses  of  melted  matter  which  have 
filled  rents,  are  often  parallel.  Assuming  then,  that  veins  are  simply 
fissures  in  which  chemical  and  mechanical  deposits  have  accumulated, 
we  may  next  consider  the  proofs  of  their  having  been  filled  gradually 
and  often  during  successive  enlargements.  I  have  already  spoken  of 
parallel  layers  of  clay,  quartz,  and  ore.  Werner  himself  observed,  in  a 
vein  near  Gersdorff,  in  Saxony,  no  less  than  thirteen  beds  of  different 

*  Conyb.  and  Phil.  Geol.  p.  401 ;  and  Farey's  Derbysh.  p.  243. 
f  Carne,  Trans,  of  Geol.  Soc.  Cornwall,  vol.  iii.  p.  238. 
j  Fournet,  Etudes  sur  les  Depots  Me"talliferes. 


CH.  XXXVIIL] 


ENLARGEMENTS  OF  VEINS. 


623 


minerals,  arranged  with  the  utmost  regularity  on  each  side  of  the  cen- 
tral layer.  This  layer  was  formed  of  two  beds  of  calcareous  spar,  which 
had  evidently  lined  the  opposite  walls  of  a  vertical  cavity.  The  thirteen 
beds  followed  each  other  in  corresponding  order,  consisting  of  fluor-spar, 
heavy  spar,  galena,  &c.  In  these  cases,  the  central  mass  has  been  last 
formed,  and  the  two  plates  which  coat  the  outer  walls  of  the  rent  on 
each  side  are  the  oldest  of  all.  If  they  consist  of  crystalline  precipi- 
tates, they  may  be  explained  by  supposing  the  fissure  to  have  remained 
unaltered  in  its  dimensions,  while  a  series  of  changes  occurred  in  the 
nature  of  the  solutions  which  rose  up  from  below ;  but  such  a  mode  of 
deposition,  in  the  case  of  many  successive  and  parallel  layers,  appears  to 
be  exceptional. 

If  a  veinstone  consist  of  crystalline  matter,  the  points  of  the  crystals 
are  always  turned  inwards,  or  towards  the  centre  of  the  vein ;  in  other 
words,  they  point  in  that  direction  where  there  was  most  space  for  the 
development  of  the  crystals.  Thus  each  new  layer  receives  the  im- 
pression of  the  crystals  of  the  preceding  layer,  and  imprints  its  crystals 
on  the  one  which  follows,  until  at  length  the  whole  of  the  vein  is  filled : 
the  two  layers  which  meet  dovetail  the  points  of  their  crystals  the  one 
into  the  other.  But  in  Cornwall,  some  lodes  occur  where  the  vertical 
plates,  or  combs,  as  they  are  there  called,  exhibit  crystals  so  dovetailed 
as  to  prove  that  the  same  fissure  has  been  often  enlarged.  Sir  H.  De 
la  Beche  gives  the  following  curious  and  instructive  example  (fig.  713) 


Fig.  713. 


Copper  lode,  near  Redruth,  enlarged  at  six  successive  periods. 

from  a  copper-mine  in  granite,  near  Redruth.*  Each  of  the  plates  or 
combs  (a,  b,  c,  d,  e,  /)  are  double,  having  the  points  of  their  crystals 
turned  inwards  along  the  axis  of  the  comb.  The  sides  or  walls  (2,  3, 
4,  5,  and  6)  are  parted  by  a  thin  covering  of  ochreous  clay,  so  that  each 
comb  is  readily  separable  from  another  by  a  moderate  blow  of  the  ham- 
mer. The  breadth  of  each  represents  the  whole  width  of  the  fissure  at 
six  successive  periods,  and  the  outer  walls  of  the  vein,  where  the  first 
narrow  rent  was  formed,  consisted  of  the  granitic  surfaces  1  and  7. 

A  somewhat  analogous  interpretation  is  applicable  to  numbers  of  other 
cases,  where  clay,  sand,  or  angular  detritus,  alternate  with  ores  and 
veinstones.    Thus,  we  may  imagine  the  sides  of  a  fissure  to  be  encrusted 
*  Geol.  Rep.  on  Cornwall,  p.  340. 


624  SWELLING  OUT  OF  VEINS.  [Cn.  XXXVIII. 

with  siliceous  matter,  as  Von  Buch  observed,  in  Lancerote,  the  walls  of 
a  volcanic  crater  formed  in  1731  to  be  traversed  by  an  open  rent  in 
which  hot  vapours  had  deposited  hydrate  of  silica,  the  incrustation 
nearly  extending  to  the  middle.*  Such  a  vein  may  then  be  filled  with 
clay  or  sand,  and  afterwards  reopened,  the  new  rent  dividing  the  argil- 
laceous deposit,  and  allowing  a  quantity  of  rubbish  to  fall  down.  Yarious 
metals  and  spars  may  then  be  precipitated  from  aqueous  solutions  among 
the  interstices  of  this  heterogeneous  mass. 

That  such  changes  have  repeatedly  occurred,  is  demonstrated  by  oc- 
casional cross-veins,  implying  the  oblique  fracture  of  previously  formed 
chemical  and  mechanical  deposits.  Thus,  for  example,  M.  Fournet,  in 
his  description*  of  some  mines  in  Auvergne  worked  under  his  superin- 
tendence, observes,  that  the  granite  of  that  country  was  first  penetrated 
by  veins  of  granite,  and  then  dislocated,  so  that  open  rents  crossed  both 
the  granite  and  the  granitic  veins.  Into  such  openings,  quartz,  accom- 
panied by  sulphurets  of  iron  and  arsenical  pyrites,  was  introduced. 
Another  convulsion  then  burst  open  the  rocks  along  the  old  line  of  frac- 
ture, and  the  first  set  of  deposits  were  cracked  and  often  shattered,  so 
that  the  new  rent  was  filled,  not  only  with  angular  fragments  of  the 
adjoining  rocks,  but  with  pieces  of  the  older  veinstones.  Polished  and 
striated  surfaces  on  the  sides  or  in  the  contents  of  the  vein,  also  attest 
the  reality  of  these  movements.  A  new  period  of  repose  then  ensued, 
during  which  various  sulphurets  were  introduced,  together  with  horn- 
stone  quartz,  by  which  angular  fragments  of  the  older  quartz  before 
mentioned  were  cemented  into  a  breccia.  This  period  was  followed  by 
other  dilatations  of  the  same  veins,  and  other  sets  of  mineral  deposits, 
until,  at  last,  pebbles  of  the  basaltic  lavas  of  Auvergne,  derived  from 
superficial  alluviums,  probably  of  Miocene  or  older  Pliocene  date,  were 
swept  into  the  veins.  I  have  not  space  to  enumerate  all  the  changes 
minutely  detailed  by  M.  Fournet,  but  they  are  valuable,  both  to  the 
miner  and  geologist,  as  showing  how  the  supposed  signs  of  violent  catas- 
trophes may  be  the  monuments,  not  of  one  paroxysmal  shock,  but  of 
reiterated  movements. 

Such  repeated  enlargement  and  reopening  of  veins  might  have  been 
anticipated,  if  we  adopt  the  theory  of  fissures,  and  reflect  how  few  of 
them  have  ever  been  sealed  up  entirely,  and  that  a  country  with  fissures 
only  partially  filled  must  naturally  offer  much  feebler  resistance  along 
the  old  lines  of  fracture  than  any  where  else.  It  is  quite  otherwise  in 
the  case  of  dikes,  where  each  opening  has  been  the  receptacle  of  one 
continuous  and  homogeneous  mass  of  melted  matter,  the  consolidation 
of  which  has  taken  place  under  considerable  pressure.  Trappean  dikes 
can  rarely  fail  to  strengthen  the  rocks  at  the  points  where  before  they 
were  weakest ;  and  if  the  upheaving  force  is  again  exerted  in  the  same 
direction,  the  crust  of  the  earth  will  give  way  anywhere  rather  than  at 
the  precise  points  where  the  first  rents  were  produced. 

*  Principles,  ch.  xxvii  8th  ed.  p.  422. 


Cs.  XXXVIIL]  SWELLING  OUT  OF  VEINS.  625 

A  large  proportion  of  metalliferous  veins  have  Uieir  opposite  walls 
nearly  parallel,  and  sometimes  over  a  wide  extent  of  country.  There 
is  a  fine  example  of  this  in  the  celebrated  vein  of  Andreasburg  in  the 
Hartz,  which  has  been  worked  for  a  depth  of  500  yards  perpendicularly, 
and  200  horizontally,  retaining  almost  every  where  a  width  of  3  feet. 
But  many  lodes  in  Cornwall  and  elsewhere  are  extremely  variable  in 
size,  being  one  or  two  inches  in  one  part,  and  then  8  or  10  feet  in  an- 
other, at  the  distance  of  a  few  fathoms,  and  then  again  narrowing  as 
before.  Such  alternate  swelling  and  contraction  is  so  often  characteristic 
as  to  require  explanation.  The  walls  of  fissures  in  general,  observes  Sir 
H.  De  la  Beche,  are  rarely  perfect  planes  throughout  their  entire  course, 
nor  could  we  well  expect  them  to  be  so,  since  they  commonly  pass 
through  rocks  of  unequal  hardness  and  different  mineral  composition. 
If,  therefore,  the  opposite  sides  of  such  irregular  fissures  slide  upon  each 
other,  that  is  to  say,  if  there  be  a  fault,  as  in  the  case  of  so  many  mineral 
veins,  the  parallelism  of  the  opposite  walls  is  at  once  entirely  destroyed, 
as  will  be  readily  seen  by  studying  the  annexed  diagrams. 

Fig.  T14. 


Fig.  715. 

^                                                                                                                        -? 

—  £_«B£»£i'V 

cf-                                                                                a> 

^d^ 

Fig.  716. 

Let  a  b,  fig.  714,  be  a  line  of  fracture  traversing  a  rock,  and  let  a  bf 
fig.  715,  represent  the  same  line.  Now,  if  we  cut  a  piece  of  paper  re- 
presenting this*  line,  and  then  move  the  lower  portion  of  this  cut  paper 
sideways  from  a  to  a',  taking  care  that  the  two  pieces  of  paper  still  touch 
each  other  at  the  points  1,  2,  3,  4,  5,  we  obtain  an  irregular  aperture  at 
c,  and  insolated  cavities  at  d  d  d,  and  when  we  compare  such  figures 
with  nature  we  find  that,  with  certain  modifications,  they  represent  the 
interior  of  faults  and  mineral  veins.  If,  instead  of  sliding  the  cut  paper 
to  the  right  hand,  we  move  the  lower  part  towards  the  left,  about  the 
same  distance  that  it  was  previously  slid  to  the  right,  we  obtain  consid- 
erable variation  in  the  cavities  so  produced,  two  long  irregular  open  spa- 
ces, //,  fig.  7 1 6,  being  then  formed.  This  will  serve  to  show  to  what  slight 
circumstances  considerable  variations  in  the  character  of  the  openings 
between  unevenly  fractured  surfaces  may  be  due,  such  surfaces  being 
moved  upon  each  other,  so  as  to  have  numerous  points  of  contact. 

Most  lodes  are  perpendicular  to  the  horizon,  or  nearly  so ;  but  some 
of  them  have  a  considerable  inclination  or  "  hade,"  as  it  is  termed,  the 
angles  of  dip  varying  from  15°  to  45°.  The  course  of  a  vein  is  frequent- 
ly very  straight ;  but  if  tortuous,  it  is  found  to  be  choked  up  with  clay, 

40 


626  CHEMICAL  DEPOSITS  IN  VEINS.         [Ca  XXXVIII 

stones,  and  pebbles,  at  points  where  it  departs  most  widely         Fig.  7i". 
from  vertically.     Hence  at  places,  such  as  a,  fig.  717,  the 
miner  complains  that  the  ores  are  "  nipped,"  or  greatly 
reduced  in  quantity,  the  space  for  their  free  deposition 
having  been  interfered  with  in  consequence  of  the  pre- 
occupancy  of  the  lode  by  earthy  materials.     When  lodes 
are  many  fathoms  wide,  they  are  usually  filled  for  the  most 
part  with  earthy  matter,  and  fragments  of  rock,  through 
which  the  ores  are  much  disseminated.    The  metallic  sub- 
stances frequently  coat  or  encircle  detached  pieces  of  rock, 
which  our  miners  call  "  horses"  or  "  riders."     That  we  should  find  some 
mineral  veins  which  split  into  branches  is  also  natural,  for  we  observe  the 
same  in  regard  to  open  fissures. 

Chemical  deposits  in  veins. — If  we  now  turn  from  the  mechanical  to  the 
chemical  agencies  which  have  been  instrumental  in  the  production  of 
mineral  veins,  it  may  be  remarked  that  those  parts  of  fissures  which  were 
not  choked  up  with  the  ruins  of  fractured  rocks  must  always  have  been 
filled  with  water ;  and  almost  every  vein  has  probably  been  the  channel 
by  which  hot  springs,  so  common  in  countries  of  volcanos  and  earth- 
quakes, have  made  their  way  to  the  surface.  For  we  know  that  the 
rents  in  which  ores  abound  extend  downwards  to  vast  depths,  where  the 
temperature  of  the  interior  of  the  earth  is  more  elevated.  We  also 
know  that  mineral  veins  are  most  metalliferous  near  the  contact  of  plu- 
tonic  and  stratified  formations,  especially  where  the  former  sends  veins 
into  the  latter,  a  circumstance  which  indicates  an  original  proximity  of 
veins  at  their  inferior  extremity  to  igneous  and  heated  rocks.  It  is  more- 
over acknowledged  that  even  those  mineral  and  thermal  springs,  which, 
in  the  present  state  of  the  globe,  are  far  from  volcanos,  are  nevertheless 
observed  to  burst  out  along  great  lines  of  upheaval  and  dislocation  of 
rocks.*  It  is  also  ascertained  that  all  the  substances  with  which  hot 
springs  are  impregnated  agree  with  those  discharged  in  a  gaseous  form 
volcanos.  Many  of  these  bodies  occur  as  veinstones ;  such  as  silex, 
carbonate  of  lime,  sulphur,  fluor-spar,  sulphate  of  barytes,  magnesia, 
oxide  of  iron,  and  others.  I  may  add  that,  if  veins  have  been  filled 
with  gaseous  emanations  from  masses  of  melted  matter,  slowly  cooling  in 
the  subterranean  regions,  the  contraction  of  such  masses  as  they  pass 
from  a  plastic  to  a  solid  state  would,  according  to  the  experiments  of 
Deville  on  granite  (a  rock  which  may  be  taken  as  a  standard),  produce 
a  reduction  in  volume  amounting  to  10  per  cent.  The  slow  crystalliza- 
tion, therefore,  of  such  plutonic  rocks  supplies  us  with  a  force  not  only 
capable  of  rending  open  the  incumbent  rocks  by  causing  a  failure  of 
support,  but  also  of  giving  rise  to  faults  whenever  one  portion  of  the 
earth's  crust  subsides  slowly  while  another  contiguous  to  it  happens  to 
rest  on  a  different  foundation,  so  as  to  remain  unmoved. 

Although  we  are  led  to  infer,  from  the  foregoing  reasoning,  that  there 

*  See  Dr.  Daubeny's  Volcanos. 


Cn.  XXXVIII.]        CHEMICAL   DEPOSITS  IX  VEIXS.  627 

has  often  been  an  intimate  connection  between  metalliferous  veins  and 
hot  springs  holding  mineral  matter  in  solution,  yet  v?e  must  not  on 
that  account  expect  that  the  contents  of  hot  springs  and  mineral  veins 
would  be  identical.  On  the  contrary,  M.  E.  de  Beaumont  has  judi- 
ciously observed  that  we  ought  to  find  in  veins  those  substances,  which, 
being  least  soluble,  are  not  discharged  by  hot  springs, — or  that  class  of 
simple  and  compound  bodies  which  the  thermal  waters  ascending  from 
below,  would  first  precipitate  on  the  walls  of  a  fissure,  as  soon  as  their 
temperature  began  slightly  to  diminish.  The  higher  they  mount 
towards  the  surface,  the  more  will  they  cool,  till  they  acquire  the  ave- 
rage temperature  of  springs,  being  in  that  case  chiefly  charged  with  the 
most  soluble  substances,  such  as  the  alkalis,  soda,  and  potash.  /These 
are  not  met  with  in  veins,  although  they  enter  so  largely  into  the  compo- 
sition of  granitic  rocks.* 

To  a  certain  extent,  therefore,  the  arrangement  and  distribution  of 
metallic  matter  in  veins  may  be  referred  to  ordinary  chemical  action, 
or  to  those  variations  in  temporature,  which  waters  holding  the  ores  in 
solution  must  undergo,  as  they  rise  upwards  from  great  depths  in  the 
earth.  But  there  are  other  phenomena  which  do  not  admit  of  the  same 
simple  explanation.  Thus,  for  example,  in  Derbyshire,  veins  containing 
ores  of  lead,  zinc,  and  copper,  but  chiefly  lead,  traverse  alternate  beds 
of  limestone  and  greenstone.  The  ore  is  plentiful  where  the  walls  of 
the  rent  consist  of  limestone,  but  is  reduced  to  a  mere  string  when  they 
are  formed  of  greenstone,  or  "  toad-stone,"  as  it  is  called  provincially. 
Not  that  the  original  fissure  is  narrower  where  the  greenstone  occurs, 
but  because  more  of  the  space  is  there  filled  with  veinstones,  and  the 
waters  at  such  points  have  not  parted  so  freely  with  their  metallic 
contents. 

"  Lodes  in  Cornwall,"  says  Mr.  Robert  W.  Fox,  "  are  very  much 
influenced  in  their  metallic  riches  by  the  nature  of  the  rock  which  they 
traverse,  and  they  often  change  in  this  respect  very  suddenly,  in  passing 
from  one  rock  to  another.  Thus  many  lodes  which  yield  abundance 
of  ore  in  granite,  are  unproductive  in  clay-slate,  or  killas,  and  vice  versa. 
The  same  observation  applies  to  killas  and  the  granitic  porphyry  called 
elvan.  Sometimes,  in  the  same  continuous  vein,  the  granite  will  contain 
copper,  and  the  killas  tin,  or  vice  versa?\  Mr.  Fox,  after  ascertaining 
the  existence  at  present  of  electric  currents  in  some  of  the  metalliferous 
veins  in  Cornwall,  has  speculated  on  the  probability  of  the  same  cause 
having  acted  originally  on  the  sulphurets  and  muriates  of  copper,  tin, 
iron,  and  zinc,  dissolved  in  the  hot  water  of  fissures,  so  as  to  deter- 
mine the  peculiar  mode  of  their  distribution.  After  instituting  experi- 
ments on  this  subject,  he  even  endeavored  to  account  for  the  preva- 
lence of  an  east  and  west  direction  in  the  principal  Cornish  lodes  by 
their  position  at  right  angles  to  the  earth's  magnetism ;  but  Mr.  Hen- 
wood  and  other  experienced  miners  have  pointed  out  objections  to 

*  Bulletin,  iv.  p.  1278.  f  R.  TV.  Fox  on  Mineral  Veins,  p.  10. 


628  RELATIVE  AGE   OF  METALS.  [Ca.  XXXVIIL 

the  theory ;  and  it  must  be  owned  that  the  direction  of  veins  in  different 
mining  districts  varies  so  entirely  that  it  seems  to  depend  on  lines  of 
fracture,  rather  than  on  the  laws  of  voltaic  electricity.  Nevertheless,  as 
different  kinds  of  rock  would  be  often  in  different  electrical  conditions, 
we  may  readily  believe  that  electricity  must  often  govern  the  arrange- 
ment of  metallic  precipitates  in  a  rent. 

"  I  have  observed,"  says  Mr.  R  Fox,  "  that  when  chloride  of  tin  in 
solution  is  placed  in  the  voltaic  circuit,  part  of  the  tin  is  deposited  in  a 
metallic  state  at  the  negative  pole,  and  part  at  the  positive  one,  in  the 
state  of  a  peroxide,  such  as  it  occurs  in  our  Cornish  mines.  This  experi- 
ment may  serve  to  explain  why  tin  is  found  contiguous  to,  and  inter- 
mixed .with,  copper  ore,  and  likewise  separated  from  it,  in  other  parts 
of  the  same  lode."* 

Relative  age  of  the  different  metals.  — After  duly  reflecting  on  the 
facts  above  described,  we  cannot  doubt  that  mineral  veins,  like  eruptions 
of  granite  or  trap,  are  referable  to  many  distinct  periods  of  the  earth's 
history,  although  it  may  be  more  difficult  to  determine  the  precise  age 
of  veins ;  because  they  have  often  remained  open  for  ages,  and  because, 
as  we  have  seen,  the  same  fissure,  after  having  been  once  filled,  has 
frequently  been  re-opened  or  enlarged.  But  besides  this  diversity  of 
age,  it  has  been  supposed  by  some  geologists  that  certain  metals  have 
been  produced  exclusively  in  earlier,  others  in  more  modern  times,  — 
that  tin,  for  example,  is  of  higher  antiquity  than  copper,  copper  than 
lead  or  silver,  and  all  of  them  more  ancient  than  gold.  I  shall  first 
point  out  that  the  facts  once  relied  upon  in  support  of  some  of  these 
views  are  contradicted  by  later  experience,  and  then  consider  how  far 
any  chronological  order  of  arrangement  can  be  recognised  in  the  position 
of  the  precious  and  other  metals  in  the  earth's  crust.  In  the  first  place, 
it  is  not  true  that  veins  in  which  tin  abounds  are  the  oldest  lodes  worked 
in  Grent  Britain.  The  government  survey  of  Ireland  has  demonstrated, 
that  in  Wexford  veins  of  copper  and  lead  (the  latter  as  usual  being 
argentiferous)  are  much  older  than  the  tin  of  Cornwall.  In  each  of  the 
two  countries  a  very  similar  series  of  geological  changes  has  occurred  at 
two  distinct  epochs,  —  in  Wexford,  before  the  Devoniam  strata  were 
deposited;  in  Cornwall,  after  the  carboniferous  epoch.  To  begin  with 
the  Irish  mining  district :  We  have  granite  in  Wexford,  traversed  by 
granite  veins,  which  veins  also  intrude  themselves  into  the  Silurian 
strata,  the  same  Silurian  rocks  as  well  as  the  veins  having  been  denuded 
before  the  Devoniam  beds  were  superimposed.  Next  we  find,  in  the 
same  county,  that  elvans,  or  straight  dikes  of  porphyritic  granite,  have 
cut  through  the  granite  and  the  veins  before  mentioned,  but  have  not 
penetrated  the  Devonian  rocks.  Subsequently  to  these  elvans,  veins 
of  copper  and  lead  were  produced,  being  of  a  date  certainly  posterior 
to  the  Silurian,  and  anterior  to  the  Devonian ;  for  they  do  not  enter 
.the  lalter,  and,  what  is  still  more  decisive,  streaks  or  layers  of 

*  E.  W.  Fox  on  Mineral  Veins,  p.  38. 


CH.  XXXVIII]  RELATIVE  AGE   OF  METALS.  629 

derivative  copper  have  been  found  near  Wexford  in  the  Devonian, 
not  far  from  points  where  mines  of  copper  are  worked  in  the  Silurian 
strata.* 

Although  the  precise  age  of  such  copper  lodes  cannot  be  defined,  we 
may  safely  affirm  that  they  were  either  filled  at  the  close  of  the  Silurian 
or  commencement  of  the  Devonian  period.  Besides  copper,  lead,  and 
silver,  there  is  some  gold  in  these  ancient  or  primary  metalliferous  veins. 
A  few  fragments  also  of  tin  found  in  Wicklow  in  the  drift  are  supposed 
to  have  been  derived  from  veins  of  the  same  age.f 

Next,  if  we  turn  to  Cornwall,  we  find  there  also  the  monuments  of  a 
very  analogous  sequence  of  events.  First  the  granite  was  formed ;  then, 
about  the  same  period,  veins  of  fine-grained  granite,  often  tortuous  (see 
fig.  692.,  p.  569.),  penetrating  both  the  outer  crust  of  granite  and  the 
adjoining  fossiliferous  or  primary  rocks,  including  the  coal-measures; 
thirdly,  elvans,  holding  their  course  straight  through  granite,  granitic 
veins,  and  fossiliferous  slates;  fourthly,  veins  of  tin  also  containing 
copper,  the  first  of  those  eight  systems  of  fissures  of  different  ages  already 
alluded  to,  p.  621.  Here,  then,  the  tin  lodes  are  newer  than  the  elvans. 
It  has  indeed  been  stated  by  some  Cornish  miners  that  the  elvans  are 
in  some  few  instances  posterior  to  the  oldest  tin-bearing  lodes,  but  the 
observations  of  Sir  H.  de  la  Beche  during  the  survey  led  him  to  an 
opposite  conclusion,  and  he  has  shown  how  the  cases  referred  to  in 
corroboration  can  be  otherwise  interpreted.!  We  may,  therefore,  assert 
that  the  most  ancient  Cornish  lodes  are  younger  than  the  coal-measures 
of  that  part  of  England,  and  it  follows  that  they  are  of  a  much  later 
date  than  the  Irish  copper  and  lead  of  Wexford  and  some  adjoining 
counties.  How  much  later  it  is  not  so  easy  to  declare,  although  pro- 
bably they  are  not  newer  than  the  beginning  of  the  Permian  period,  as 
no  tin  lodes  have  been  discovered  in  any  red  sandstone  of  the  Poikilitic 
group,  which  overlies  the  coal  in  the  south-west  of  England. 

There  are  lead  veins  in  the  Mendip  hills  which  extend  through  the 
mountain  limestone  into  the  Permian  or  Dolomitic  conglomerate,  and 
others  in  Glamorganshire  which  enter  the  lias.  Those  worked  near 
Frome,  in  Somersetshire,  have  been  traced  into  the  Inferior  Oolite.  In 
Bohemia,  the  rich  veins  of  silver  of  Joachimsthal  cut  through  basalt  con- 
taining olivine,  which  overlies  tertiary  lignite,  in  which  are  leaves  of 
dicotyledonous  trees.  This  silver,  therefore,  is  decidedly  a  tertiary  for- 
mation. In  regard  to  the  age  of  the  gold  of  the  Ural  Mountains,  in 
Russia,  which,  like  that  of  California,  is  obtained  chiefly  from  auriferous 
alluvium,  it  occurs  in  veins  of  quartz  in  the  schistose  and  granitic  rocks 
of  that  chain,  and  is  supposed  by  MM.  Murchison,  De  Verneuil,  and  Key- 
serling  to  be  newer  than  the  syenitic  granite  of  the  Ural — perhaps  of  ter- 
tiary date.  They  observe,  that  no  gold  has  yet  been  found  in  the  Per- 

*  I  am  indebted  to  Sir  H.  de  la  Beche  for  this  information.  See  also  mapa 
and  sections  of  Irish  Survey. 

f  Sir  H.  de  la  Beche,  MS.  notes  on  Irish  Survey, 
j  Report  on  Geology  of  Cornwall,  p.  310. 


630  GOLD   OF  AUSTRALIA.  [Cn.  XXXVIII. 

mian  conglomerates  which  lie  at  the  base  of  the  Ural  Mountains,  although 
large  quantities  of  iron  and  copper  detritus  are  mixed  with  the  pebbles  of 
those  Permian  strata.  Hence  it  seems  that  the  Uralian  quartz  veins,  con- 
taining gold  and  platinum,  were  not  formed  or  certainly  not  exposed  to 
aqueous  denudation  during  the  Permian  era. 

In  the  auriferous  alluvium  of  Russia,  California,  and  Australia,  the 
bones  of  extinct  land-quadrupeds,  have  been  met  with,  those  of  the  mam- 
moth being  common  in  the  gravel  at  the  foot  of  the  Ural  Mountains, 
while  in  Australia  they  consist  of  huge  marsupials,  some  of  them  of  the 
size  of  the  rhinoceros  and  allied  to  the  living  wombat.  They  belong  to 
the  genera  Diprotodon  and  Nototherium  of  Professor  Owen.  The  gold 
of  Northern  Chili  is  associated  in  the  mines  of  Los  Hornos  with  copper 
pyrites,  in  veins  traversing  the  cretaceo-oolitic  formations,  so  called  be- 
cause its  fossils  have  the  character  partly  of  the  cretaceous  and  partly  of 
the  oolitic  fauna  of  Europe.*  The  gold  found  in  the  United  States,  in 
the  mountainous  parts  of  Virginia,  North  and  South  Carolina,  and  Georgia, 
occurs  in  rnetarnorphic  Silurian  strata,  as  well  as  in  auriferous  gravel  de- 
rived from  the  same.  v 

Gold  has  now  been  detected  in  almost  every  kind  of  rock,  in  slate, 
quartzite,  sandstone,  limestone,  granite,  and  serpentine,  both  in  veins  and 
in  the  rocks  themselves  at  shoiX  distances  from  the  veins.  In  Australia 
it  has  been  worked  successfully  not  only  in  alluvium,  but  in  veinstones  in 
the  native  rock,  generally  consisting  of  Silurian  shales  and  slates.  It  has 
been  traced  on  that  continent,  over  more  than  nine  degrees  of  latitude 
(between  the  parallels  of  the  30°  and  39°  S.),  and  over  twelve  of  longi- 
tude, and  yields  already  an  annual  supply  equal,  if  not  superior,  to  that 
of  California ;  nor  is  there  any  apparent  prospect  of  this  supply  diminish- 
ing, still  less  of  the  exhaustion  of  the  gold  fields.  It  seems  reasonable, 
therefore,  to  share  the  anticipations  of  M.  Delesse  that  the  time  will  come, 
and  cannot  be  very  remote,  when  a  marked  depreciation  will  be  experi- 
enced in  the  value  of  this  metal.f 

It  has  been  remarked  by  M.  de  Beaumont,  that  lead  and  some  other 
metals  are  found  in  dikes  of  basalt  and  greenstone,  as  well  as  in  mineral 
veins  connected  with  trap  rocks,  whereas  tin  is  met  with  in  granite  and 
in  veins  associated  with  the  granitic  series.  If  this  rule  hold  true 
generally,  the  geological  position  of  tin  in  localities  accessible  to  the 
miners,  will  belong,  tfor  the  most  part,  to  rocks  older  than  those  bearing 
lead.  The  tin  veins  will  be  of  higher  relative  antiquity  for  the  same 
reason  that  the  "underlying"  igneous  formations  or  granites  which 
are  visible  to  man  are  older,  on  the  whole,  than  the  overlying  or  trap- 
pean  formations. 

If  different  sets  of  fissures,  originating  simultaneously  at  different 
levels  in  the  earth's  crust,  and  communicating,  some  of  them,  with 
volcanic,  others  with  heated  plutonic  masses,  be  filled  with  different 

*  Darwin's  S.  America,  p.  209,  &c. 

f  Annales  des  Mines,  1853,  torn.  iii.  p.  185. 


CH.  XXXVIII]  CONCLUDING  EEMARKS.  631 

metals,  it  will  follow  that  those  formed  farthest  from  the  surface  will 
usually  require  the  longest  time  before  they  can  be  exposed  superficially. 
In  order  to  bring  them  into  view,  or  within  reach  of  the  miner,  a  greater 
amount  of  upheaval  and  denudation  must  take  place  in  proportion  as 
they  have  lain  deeper  when  first  mowed.  A  considerable  series  of  geo- 
logical revolutions  must  intervene  before  any  part  of  the  fissure,  which 
has  been  for  ages  in  the  proximity  of  the  plutonic  rocks,  so  as  to  receive 
the  gases  discharged  from  it  when  it  was  cooling,  can  emerge  into  the 
atmosphere.  But  I  need  not  enlarge  on  this  subject,  as  the  reader  will 
remember  what  was  said  in  the  30th,  34th,  and  37th  chapters,  on  the 
chronology  of  the  volcanic  and  hypogene  formations. 


Concluding  Remarks.  —  The  theory  of  the  origin  of  the  hypogene 
rocks,  at  a  variety  of  successive  periods,  as  expounded  in  two  of  the 
chapters  just  cited,  and  still  more  the  doctrine  that  such  rocks  may  be 
now  in  the  daily  course  of  formation,  has  made  and  still  makes  its  way. 
but  slowly,  into  favor.  The  disinclination  to  embrace  it  has  arisen 
partly  from  an  inherent  obscurity  in  the  very  nature  of  the  evidence  of 
plutonic  action  when  developed  on  a  great  scale,  at  particular  periods 
It  has  also  sprung,  in  some  degree,  from  extrinsic  considerations;  many 
geologists  having  been  unwilling  to  believe  the  doctrine  of  the  transmu- 
tation of  fossiliferous  into  crystalline  rocks,  because  they  were  desirous 
of  finding  proofs  of  a  beginning,  and  of  tracing  back  the  history  of  our 
terraqueous  system  to  times  anterior  to  the  creation  of  organic  beings. 
But  if  these  expectations  have  been  disappointed,  if  we  have  found  it 
impossible  to  assign  a  limit  to  that  time  throughout  which  it  has  pleased 
an  Omnipotent  and  Eternal  Being  to  manifest  his  creative  power,  we 
have  at  least  succeeded  beyond  all  hope  in  carrying  back  our  researches 
to  times  antecedent  to  the  existence  of  man.  We  can  prove  that  man 
had  a  beginning,  and  that,  all  the  species  now  contemporary  with  man, 
and  many  others  which  preceded,  had  also  a  beginning, 'and  that,  conse- 
quently, the  present  state  of  the  organic  world  has  not  gone  on  from  all 
eternity,  as  some  philosophers  have  maintained. 

It  can  be  shown  that  the  earth's  surface  has  been  remodelled  again 
and  again ;  mountain  chains  have  been  raised  or  sunk ;  valleys  formed, 
filled  up,  and  then  re-excavated ;  sea  and  land  have  changed  places ; 
yet  throughout  all  these  revolutions,  and  the  consequent  alterations  of 
local  and  general  climate,  animal  and  vegetable  life  has  been  sustained. 
This  has  been  accomplished  without  violation  of  the  laws  now  governing 
the  organic  creation,  by  which  limits  are  assigned  to  the  variability  of 
species.  The  succession  of  living  beings  appears  to  have  been  continued 
not  by  the  transmutation  of  species,  but  by  the  introduction  into  the 
earth  from  time  to  time  of  new  plants  and  animals,  and  each  assemblage 
of  new  species  must  have  been  admirably  fitted  for  the  new  states  of 
the  globe  as  they  arose,  or  they  would  not  have  increased  and  multiplied 
and  endured  for  indefinite  periods.* 


632  CONCLUDING-  REMARKS.  [Cfl.  XXXVIII 

Astronomy  has  been  unable  to  establish  the  plurality  of  habitable 
worlds  throughout  space,  however  favourite  a  subject  of  conjecture  and 
speculation ;  but  geology,  although  it  cannot  prove  that  other  planets 
are  peopled  with  appropriate  races  of  living  beings,  has  demonstrated 
the  truth  of  conclusions  scarcely  less  wonderful,  —  the  existence  on  our 
own  planet  of  so  many  habitable  surfaces,  or  worlds  as  they  have  been 
called,  each  distinct  in  time,  and  peopled  with  its  peculiar  races  of 
aquatic  and  terrestrial  beings. 

The  proofs  now  accumulated  of  the  close  analogy  between  extinct 
and  recent  species  are  such  as  to  leave  no  doubt  on  the  mind  that  the 
same  harmony  of  parts  and  beauty  of  contrivance  which  we  admire  in 
the  living  creation,  has  equally  characterized  the  organic  world  at  remote 
periods.  Thus  as  we  increase  our  knowledge  of  the  inexhaustible  variety 
displayed  in  living  nature,  and  admire  the  infinite  wisdom  and  power 
which  it  displays,  our  admiration  is  multiplied  by  the  reflection,  that  it 
is  only  the  last  of  a  great  series  of  pre-existing  creations,  of  which  we 
cannot  estimate  the  number  or  limit  in  times  past.f 

*  See  Principles  of  Geol.,  Book  3. 

f  See  the  author's  Anniv.  Address  to  the  Geol,  Soc.  1837.  Proceedings  G.  8. 
vol.  ii.  p.  620. 


SUPPLEMENT 


LONDON,  APRIL  25,  1857. 


SUPPLEMENT 


BRITISH   PLIOCENE    STRATA. 

British  Pliocene  Strata — Proofs  from  fossil  shells  of  a  gradual  refrigeration  of 
climate  in  England,  at  the  successive  periods  of  the  Coralline,  the  Bed,  and 
the  Norwich  Crag — Searles  "Wood's  Monograph  on  the  Crag  Mollusca.  The 
Crag  Mastodon,  a  Pliocene  species — Different  assemblages  of  fossil  Mammalia 
in  the  freshwater  and  drift  deposits  of  the  Valley  of  the  Thames — Fossil 
Musk-buffalo  in  the  drift  near  London  and  near  Berlin. 

SINCE  the  appearance  of  the  fifth  edition  of  this  work,  Mr.  Searles 
Wood  has  brought  to  a  conclusion  his  important  Monograph  on  the 
Crag  and  Upper  Tertiary  shells  of  Britain.*  The  results  of  his  con- 
scientious examination  of  so  many  hundred  species  of  testacea,  in  so 
far  as  they  bear  on  Geology,  will  be  found  to  agree  with  the  classifica- 
tion adopted  in  the  text  (pp.  152 — 165,  &c.),  especially  as  relates  to 
the  position  of  the  several  divisions  of  the  Crag  in  the  great  European 
series  of  formations.  But  we  may  also  deduce  from  the  same  Mono- 
graph clear  evidence  of  a  gradual  refrigeration  of  climate,  which  went 
on  in  the  area  of  England  from  the  time  of  the  older  to  that  of  the  most 
modern  Pliocene  strata,  a  refrigeration  which  was  inferred  from  the 
Crag  shells  in  1846,  by  the  late  Edward  Forbes.f  No  analysis  of  this 
excellent  treatise  has  been  drawn  up  for  us  by  Mr.  Wood  himself:  we 
have  therefore  inserted  the  following  tables,  to  point  out  many  general 
conclusions  to  which  the  conchological  data  seem  to  lead.  In  drawing 
them  up  I  have  had  the  able  assistance  of  Mr.  S.  P.  Woodward,  the 
well-known  author  of  the  "Manual  of  the  Mollusca,  Recent  and 
Fossil."! 

Number  of  known  Species  of  Marine  Testacea  in  the  three  English 
Pliocene  Deposits,  called  the  Norwich,  the  Red,  and  the  Coralline 
Crags. 

Brachiopoda  G 

Conchifera        -        -        -        -    206 

Gasteropoda      ....    230 

Total-        -        -        -    442 

6  Paleontographical  Society,  1848  to  1856. 

f  Mem.  of  Geol.  Survey,  London,  1846,  p.  391. 

J  London:  1853-6. 


636  BRITISH  PLIOCENE  STRATA. 

Distribution  of  the  above  Marine  Testacea. 

Number  of  Species.  Species  common  to  the 


Norwich  Crag  81 

Red  Crag  -        -        -        -225 

Coralline  Crag  -        -        -    327 


Norwich  and  Red  Crag  (not  in  Cor.)  33 
Norwich  and  Coralline  (not  in  Red)  4 
Red  and  Coralline  (not  in  Norwich)  116 
Norwich,  Red,  and  Coralline  -  19* 

Proportion  of  Recent  to  Extinct  Species. 

Percentage  of 
Recent  Extinct  Eecent 

Norwich  Crag      ....      69  12  85 

Red  Crag 130  95  57 

Coralline  Crag     -        -        -        -    168  159  51 

Recent  Species  not  living  now  in  British  Seas. 

Northern  Species.  Southern. 

Norwich  Crag                             -    12  0 

Red  Crag          ....      8  16 

Coralline  Crag          ...      2  27 

lu  the  above  list  I  have  not  concluded  the  shells  of  the  glacial  beds 
of  the  Clyde  and  of  several  other  British  deposits  of  newer  origin  than 
the  Norwich  Crag,  in  which  nearly  all — perhaps  all — the  species  are 
recent,  although  such  fossils  are  described  by  Mr.  Wood,  or  enumer- 
ated in  his  Appendix.  The  land  and  freshwater  shells,  32  in  number, 
have  also  been  purposely  omitted,  as  well  as  three  species  of  London 
Clay  shells,  suspected  by  Mr.  Wood  himself  to  be  spurious. 

By  far  the  greater  number  of  the  recent  marine  species  included  in 
these  tables  are  still  inhabitants  of  the  British  seas ;  but  even  these  dif- 
fer considerably  in  their  relative  abundance,  some  of  the  commonest  of 
the  Crag  shells  being  now  extremely  scarce ;  as,  for  example,  JBuccinum 
Dalei,  and  others,  rarely  met  with  in  a  fossil  state,  being  now  very  com- 
mon, as  Murex  erinaceus  and  Cardium  echinatum. 

The  last  table  throws  light  on  a  marked  alteration  in  the  climate  of 
the  three  successive  periods.  It  will  be  seen  that  in  the  Coralline  Crag, 
there  are  27  Southern  shells,  including  26  Mediterranean,  and  one 
West  Indian  species  (Erato  Maugerce).  Of  these  only  13  occur  in  the 
Red  Crag,  associated  with  3  new  Southern  species,  while  the  whole  of 
them  disappear  from  the  Norwich  beds.  On  the  other  hand,  the  Coral- 
line Crag  contains  only  2  Arctic  shells,  Admete  viridula  and  Limopsis 
pygmcea ;  whereas  the  Red  Crag  contains,  as  stated  in  the  table,  8 
Northern  species,  all  of  which  recur  in  the  Norwich  Crag,  with  the 
addition  of  4  others,  also  inhabitants  of  the  Arctic  regions ;  so  that 
there  is  good  evidence  of  a  continual  refrigeration  of  climate  during 
the  Pliocene  period  in  Britain.  The  presence  of  these  Northern  shells 
cannot  be  explained  away  by  supposing  that  they  were  inhabitants  of 
the  deep  parts  of  the  Sea ;  for  some  of  them,  such  as  Tellina  calcarea 
and  Astarte  borealis,  occur  plentifully,  and  sometimes  with  the  valves 

0  These  19  species  must  be  added  to  the  numbers  33-4  and  116  respectively, 
in  order  to  obtain  the  full  amount  of  common  species  in  each  of  those  cases. 


MASTODON  OF  NORWICH  CRAG.  637 

united  by  their  ligament,  in  company  with  other  littoral  shells,  such  as 
Mya  arenaria  and  Littorina  rudis,  and  evidently  not  thrown  up  from 
deep  water.  Yet  the  northern  character  of  the  Norwich  Crag  is  not 
fully  shown  by  simply  saying  that  it  contains  12  Northern  species  now 
no  longer  found  in  British  seas,  since  several  boreal  shells  which  still 
linger  in  the  Scottish  deeps  do  not  abound  there  as  they  did  in  the  lat- 
ter days  of  the  Crag  Period.  It  is  the  predominance  of  certain  genera 
and  species  which  satisfies  the  mind  of  a  conchologist  as  to  the  Arctic 
character  of  the  Norwich  Crag.  In  like  manner,  it  is  the  presence  of 
such  genera  as  Pyrula,  Columbella,  Terebra,  Cassidaria,  Pholadomya^ 
Lingula,  Discina,  and  others,  which  give  a  southern  aspect  to  the  Coral- 
line Crag  shells. 

In  conclusion,  it  may  be  observed  that  the  cold  which  had  gone  on 
increasing  from  the  time  of  the  Coralline  to  that  of  the  Norwich  Crag 
continued,  though  not  perhaps  without  some  oscillations  of  temperature, 
to  become  more  and  more  severe  after  the  accumulation  of  the  latter, 
until  it  reached  its  maximum  in  what  has  been  called  the  Glacial  epoch. 
The  marine  fauna  of  this  last  period  contains,  both  in  Ireland  and  Scot- 
land, recent  species  of  mollusea  now  living  in  Greenland  and  other  seas 
far  north  of  the  areas  where  we  find  their  remains  in  a  fossil  state. 

It  is  not  in  reference  to  the  two  older  formations  above  alluded  to, 
but  when  we  attempt  to  classify  the  lacustrine  and  fluviatile  deposits 
(some  contemporaneous  with  the  marine  Norwich  Crag  and  others  pos- 
terior to  it),  that  we  encounter  in  the  East  and  South  of  England  the 
greatest  difficulty.  When  treating  of  the  Newer  Pliocene  and  drift 
formation  in  the  Valley  of  the  Thames,  I  have  acknowledged  the  per- 
plexity in  which  this  subject  is  still  involved,  and  have  hinted  at  the 
causes  of  it  (chap.  xiii.  pp.  152,  153).  Every  year,  however,  removes 
some  of  this  ambiguity ;  for  the  true  relative  position  of  distinct  sets  of 
superficial  strata  becomes  more  clearly  understood,  and  the  specific 
characters  of  the  fossil  mammalia  and  shells  better  ascertained.  In  the 
first  place,  the  occurrence  in  the  Norwich  Crag  of  many  marine  shells 
of  Northern  species,  as  before  described,  in  company  with  land  and 
freshwater  shells,  and  some  mammalia  of  a  more  Southern  character, 
may  possibly  be  explained  by  supposing  the  sea  of  the  Norwich  Crag 
to  have  been  opened  towards  the  Pole,  with  islands  interspersed,  while 
the  land  of  the  same  period  was  continuous  far  to  the  South.  In  that 
direction  a  Continent  may  have  existed,  from  which  rivers  flowed  north- 
wards, in  whose  waters  the  hippopotamus  and  such  shells  as  the  Cyrena 
consobrina  flourished. 

The  Mastodon  found  in  the  Red  and  Norwich  Crag  (p.  155,  and  fig. 
135,  p.  165)  was  till  lately  regarded  as  a  Miocene  or  Falunian  species; 
and  under  this  persuasion,  calling  it  M.  angustidens,  on  the  authority  of 
Professor  Owen,  I  suggested  that  its  remains  might  have  been  washed 
out  of  older  strata  into  the  Crag,  just  as  we  sometimes  observe  London 
Clay  and  Chalk  fossils  occasionally  introduced  into  the  same  deposit. 
Many  teeth  of  this  Mastodon,  together  with  numerous  ear-bones  of 


638  FOSSIL   MAMMALIA  IN  MODERN 

whales,  have  recently  been  found  at  Felixstow,  in  what  is  called  "  the 
detrital  bed,"  so  rich  in  phosphate  of  lime  used  in  agriculture.  That 
accumulation  of  drifted  materials  lies  at  the  base  of  the  Red  Crag,  and 
it  has  been  supposed  that  the  imbedded  mammalian  fossils  were  derived 
from  the  destruction  of  an  older  set  of  strata.  But  in  regard  to  the 
Mastodon  above  mentioned,  Dr.  Falconer,  who  has  devoted  fifteen  years 
to  the  study  of  the  fossil  and  recent  Proboscideans,  assures  me  that  the 
fossil  is  a  well-known  Pliocene  animal,  first  observed  in  Auvergne  by 
MM.  Croizet  and  Jobert,  and  called  by  them  Mastodon  arvernensis. 
Cuvier  did  not  adopt  this  name,  for  he  had  seen  but  a  few  specimens 
from  Auvergne,  and  he  confounded  it  with  M.  angustidens.  The  entire 
skeleton  of  both  these  Mastodons  having  now  been  obtained,  they  are 
found  to  be  referable  to  two  distinct  sub-genera.  The  Crag  fossil  be- 
longs to  the  Tetralophodon  of  Falconer,  a  sub-genus  of  which  five  spe- 
cies are  known,  so  called  because  there  are  four  ridges  in  the  penulti- 
mate true  molar  as  well  as  in  the  two  teeth  which  are  placed  immedi- 
ately before  it  in  both  jaws.  The  Mastodon  angustidens,  on  the  other 
hand,  belongs,  with  six  other  species,  to  the  section  called  Trilophodon, 
in  which  the  corresponding  teeth  have  each  three  ridges.  This  Masto- 
don, according  to  MM.  Lartet  and  Falconer,  is  characteristic  of  the 
Faluns  and  of  the  Molasse  at  Sansan  at  the  foot  of  the  Pyrenees,  and 
of  several  other  Miocene  localities.* 

The  Mastodon  arvernensis  is,  according  to  Dr.  Falconer,  the  only  one 
yet  found  in  England.  It  abound^  with  the  Hippopotamus  major  in 
the  Pliocene  strata  of  the  Val  d'Arno,  as  well  as  in  strata  of  the  same 
age  in  Piedmont  and  at  Montpellier.  It  may  be  considered,  therefore, 
as  a  characteristic  Pliocene  species ;  and  this  view  is  in  accordance  with 
the  fact  that  its  remains  are  best  preserved  in  freshwater  strata,  asso- 
ciated and  coeval  with  the  Norwich  Crag.  But  we  have  no  evidence  of 
its  surviving  in  England  till  the  still  more  modern  epoch  of  those  flu- 
viatile  deposits  in  the  valley  of  the  Thames  in  which  the  Hippopotamus 
major  and  a  species  of  monkey,  Macacus  plioccenus,  have  been  detected. 
These  freshwater  strata  are  alluded  to  in  the  text  (p.  153),  as  occurring  at 
Grays  in  Essex,  21  miles  below  London,  and  at  Ilford,  Erith,  and  other 
places  bordering  the  Thames.  They  consist  of  sand,  gravel,  and  loam, 
from  60  to  100  feet  thick,  and  often  form  a  terrace  on  each  side  of  the 
valley,  rising  to  a  much  higher  level  than  a  vast  bed  of  more  modern 
gravel,  to  which  allusion  will  presently  be  made.  At  Grays,  the  Cyrena 
consobrina  of  the  Nile  already  mentioned,  a  shell  common  to  the  Nor- 
wich Crag,  together  with  several  other  shells  no  longer  inhabitants  of 
Great  Britain,  and  some  of  them  unknown  as  living  in  any  part  of  the 
globe,  occur,  mingled  with  a  vast  majority  of  English  species  of  land 
and  freshwater  mollusca.  The  Cyrena,  which  I  supposed  till  lately  to 

0  Professor  Owen  has  given  (Quart.  Geol.  Jour.,  Feb.  1856,  p.  223),  as  a 
synonym  of  the  Crag  Mastodon,  the  name  of  M.  longirostris,  Kaup,  a  fossil  of 
the  Miocene  sands  of  Eppelsheim,  referred  by  Falconer  to  the  sub-genus  Tetralo- 
phodon. 


DEPOSITS   OF  THAMES   VALLEY.  639 

be  a  genus  unknown  in  Europe  (p.  153),  is,  as  I  learn  from  Mr.  Wood- 
ward, a  living  Sicilian  shell,  called  by  some  naturalists  C.  panormitana. 
With  these  fossils,  and  with  the  Hippopotamus  and  monkey  above 
alluded  to,  the  remains  of  Rhinoceros  leptorhinus  are  found ;  while  the 
accompanying  elephant  is  not  the  Mammoth,  as  formerly  imagined, 
but,  according  to  Dr.  Falconer,  Elephas  antiquus,  and  sometimes  E. 
priscus. 

It  is  still  a  matter  of  discussion  whether  the  submergence  of  a  great 
part  of  the  Southeast  of  England  beneath  the  sea  of  the  glacial  epoch, 
during  which  the  Northern  erratics  of  Norfolk  and  Suffolk,  and  of 
Highgate  Hill,  near  London,  were  drifted  southwards  by  ice,  took  place 
before  or  after  the  origin  of  these  deposits  at  Grays,  Ilford,  and  other 
places  on  the  banks  of  the  Thames ;  but  it  is  quite  clear  that  after  those 
fluviatile  beds  were  formed,  a  great  sheet  of  ochreous  gravel  was  spread 
out  over  the  lower  levels  of  the  same  valley,  and  in  it  we  find  buried 
the  remains  of  Arctic  quadrupeds.  This  ochreous  gravel  extends  from 
East  to  West,  from  above  Maidenhead,  through  London,  to  the  sea,  for 
a  distance  of  50  miles,  having  a  width  varying  from  2  to  9  miles,  and 
a  thickness  of  from  5  to  15  feet.*  In  many  places  it  contains  the  bones 
and  teeth  of  the  Siberian  Mammoth  (E.  primigenius)  and  Siberian 
Rhinoceros  (R.  tichorhinus),  together  with  remains  of  the  reindeer, 
horse,  and  other  quadrupeds. 

Recently  (1855)  three  fossil  skulls,  referred  by  Prof.  Owen  to  the 
Musk-buffalo  (Bubalus  moschatus),  a  well-known  living  inhabitant  of 
Arctic  regions,  have  also  been  discovered  ;  one  of  them  in  the  valley  of 
the  Thames  at  Maidenhead,  and  the  other  two  in  gravel  of  the  same 
age  near  Batheaston,  in  the  valley  of  the  Avon. 

The  same  musk-buffalo  was  met  with  about  20  years  ago  in  the  sub- 
urbs of  Berlin,  in  the  hill  called  the  Kreuzberg,  imbedded  in  northern 
drift,  and  with  it  the  Siberian  Elephant  and  Rhinoceros,  together  with 
species  of  horse,  deer,  and  ox.f 

Among  the  fossil  mammalia  of  another  locality  in  the  same  drift  of 
North  Germany,  Dr.  Hensel,  of  Berlin,  has  detected,  near  Quedlinburg, 
the  Norwegian  Lemming,  Myodes  lemmus,  and  another  species  of  the 
same  family  called  by  Pallas  Myodes  torquatus  (by  Hensel  Misother- 
mus  torquatus),  a  still  more  Arctic  quadruped  found  by  Parry  in  lati- 
tude 82°,  and  which  never  strays  farther  south  than  the  northern  borders 
of  the  woody  region.  Professor  Beyrich  also  informs  me  that  the 
remains  of  the  Rhinoceros  tichorhinus  were  obtained  at  the  same  place.J 
In  this  "  diluvium,"  as  it  is  termed  by  many,  no  instance  has  as  yet 

°  Prestwich ;  Geol.  Quart.  Joum.,  vol.  xii.  p.  131. 

f  I  was  shown  in  the  Berlin  Museum,  in  1856,  part  of  the  skull  of  the  Buba- 
lus moschatus,  correctly  named  in  the  catalogue  of  the  Museum  for  1837,  the  year 
after  its  discovery,  by  Professor  Quenstedt,  at  that  time  curator.  The  associated 
Kreuzberg  fossils  are  enumerated  in  Leonhard  and  Bronn's  Jahrbuch,  1836, 
p.  215. 

%  Zeitschrift  der  Deutsch.  Geol.  Gesellschaft,  vol.  vii.  (1855),  p.  548,  &c. 


640  CLASSIFICATION   OF   MIOCENE 

occurred  in  North  Germany  of  the  association  of  the  Hippopotamus,  or 
any  genus  which  would  indicate  a  climate  too  warm  for  the  reindeer, 
musk-ox,  or  lemming  ;  so  that  it  becomes  more  and  more  probable  that 
the  alleged  association  of  the  Mammoth  (E.  primigenius),  in  the  valley 
of  the  Thames,  with  the  hippopotamus  and  monkey  (Macacus plioccenus), 
and  a  like  mixture  of  the  bones  and  teeth  of  the  tichorhine  and  lepto- 
rhine  rhinoceroses  in  the  cliffs  of  Norfolk,  may  have  arisen  from  con- 
founding together  the  fossils  of  different  deposits  and  periods,  or  from 
an  intermixture,  due  to  natural  causes,  of  the  fossil  remains  of  more  than 
one  epoch. 

Professor  Owen  remarks,  that  as  the  musk-buffalo  has  a  constitution 
fitting  it  at  present  to  inhabit  the  high  northern  regions  of  America, 
we  can  hardly  doubt  that  its  former  companions,  the  warmly-clad  Mam- 
moth and  the  two-horned  woolly  rhinoceros  (1$.  tichorhinus),  were  in 
like  manner  capable  of  supporting  life  in  a  cold  climate.* 

To  what  part  of  the  Pliocene  Period  the  Cave  animals  of  Great 
Britain  should  be  chiefly  referred,  is  still  a  vexed  question.  There 
seems,  however,  no  reason  at  present  to  suppose  any  of  them  more  an- 
cient than  the  Norwich  Crag ;  and  many  caves  may  have  remained 
open  during  the  glacial  and  post-glacial  eras,  while  the  fauna  was  grad- 
ually changing,  so  that  the  remains  found  in  them  may  not  always  be- 
long to  strictly  contemporary  quadrupeds. 

I  have  mentioned  (p.  175)  the  occurrence  in  the  suburbs  of  Rome  of 
the  remains  of  Elephants,  and  referred  them  to  E.  primigenius ;  but, 
according  to  Dr.  Falconer,  there  is  no  well-authenticated  example  of  this 
species  having  ever  been  met  with  South  of  the  Alps.  The  specimens 
from  Monte  Mario,  and  other  localities  near  Rome,  belong,  according  to 
him,  to  E.  antiquus,  Falc.,  and  E.  meridionalis,  Nesti,  and  those  in 
Piedmont  and  Lombardy  to  the  same  species,  together  with  Elephas 
prisons. 


WHERE    TO    DRAW    THE    LINE    BETWEEN    THE    MIOCENE    AND    EOCENE 
TERTIARY    STRATA,  pp.  115,  175,  183. 

Classification  of  the  Miocene  and  Eocene  strata — Where  to  draw  the  line  be- 
tween Upper  Eocene  and  Lower  Miocene — Reasons  for  a  proposed  change  of 
nomenclature — Miocene  fossil  shells  and  quadrupeds  of  the  Sewalik  or  Sub- 
Himalayan  hills. 

I  HAVE  stated  in  the  fifteenth  chapter  (p.  183),  that  many  eminent 
geologists  consider  the  Marine  Sands  of  the  Forest  of  Fontainebleau,  to- 
gether with  their  equivalents  in  age  in  Belgium,  Germany,  and  else- 
where, as  the  base  of  the  Miocene  division  of  the  great  Tertiary  series. 

0  Geol.  Quart.  Journ.,  vol.  xii.  p.  124. 


AND    EOCENE   STRATA.  641 

Accordingly,  I  have  introduced  in  the  table,  at  p.  105,  the  name  of 
"  Lower  Miocene"  as  a  synonym  much  in  vogue  on  the  Continent  for 
strata  of  that  age,  called  by  me  "  Upper  Eocene."  It  is  unnecessary  to 
repeat  the  reasons  so  fully  set  forth  in  the  text,  which  induced  the  late 
Professor  E.  Forbes  and  me  to  employ  this  arrangement  and  nomencla- 
ture in  preference  to  one  which  throws  into  the  same  division  the  fatuns 
of  Touraine  (originally  selected  by  me  as  the  type  of  the  Miocene)  and 
a  fauna  so  distinct  as  that  of  the  Fontainebleau  Sands,  which  contains 
no  species  of  shells  in  common  with  the  "faluns,"  and  which  approaches 
so  nearly  in  the  general  character  of  its  fossils  to  the  typical  Eocene 
fauna.  I  observed,  however  (pp.  186,  187),  that  I  was  not  unprepared 
for  the  necessity  of  including  hereafter  the  deposits  above  alluded  to  in 
one  and  the  same  Miocene  Period,  should  sufficient  evidence  be  brought 
to  light  of  intermediate  and  connecting  links  between  the  Fontainebleau 
sands  or  Limburg  beds 'and  the  faluns  of  Touraine. 

In  the  course  of  the  last  two  years  some  progress  has  certainly  been 
made  in  bridging  over  the  wide  gulf  which  formerly  separated  the  so- 
called  *'  Lower  Miocene"  from  the  "  faluns,"  while  on  the  other  hand 
the  Eocene  system  is  becoming  so  comprehensive  and  so  complicated  in 
its  details  by  the  continual  intercalation  of  new  formations,  and  by  the 
addition  below  its  former  base  of  the  Thanet  sands  and  Lower  Lande- 
nian  of  Belgium,  that  the  desirability  of  limiting  its  extension  in  an  up- 
ward direction  is  becoming  more  and  more  obvious.  The  Thanet  Sands, 
moreover,  exhibit  a  testaceous  fauna,  almost  as  divergent  from  that  of 
the  Barton  clay  as  are  the  shells  of  the  Fontainebleau  Sands  from  those 
of  the  faluns ;  so  that,  if  we  comprise  the  Thanet  and  Barton  beds  in 
one  Eocene  Period,  we  may  be  called  upon,  with  almost  equal  pro- 
priety, to  class  the  Fontainebleau  and  Falunian  faunas  in  one  and  the 
same  great  Miocene  system. 

Professor  Beyrich,  in  a  recently  published  memoir  on  the  tertiary 
strata  of  the  North  of  Germany,*  has  made  known  to  us  the  existence 
of  a  long  succession  of  marine  strata,  leading  almost  gradually  from 
the  equivalents  of  the  Lowest  Limburg  or  Tongrian  beds  of  Dumont  to 
others  approaching  in  age  the  faluns  of  the  Loire.  Consequently  he 
has  thought  fit  to  introduce  a  new  term — that  of  "  Oligocene  " — for  all 
the  beds  intermediate  between  Eocene  and  Miocene ;  and,  having  dis- 
tributed the  strata  in  question  into  seven  subdivisions,  each  character- 
ized by  a  certain  proportion  of  peculiar  fossils,  he  refers  the  uppermost 
of  all,  or  his  Sternberg  beds,  to  the  "  Upper  Oligocene ;"  the  next  five, 
comprising  among  others  the  Upper  and  Middle  Limburg,  to  the  "  Mid- 
dle Oligocene ;"  and  the  remaining  two  to  the  Lower  Oligocene,  com- 
prehending the  Lower  Tongrian  of  Dumont  with  the  Brown-coal  of 
Germany,  which  is  classed  as  the  lowest  of  all. 

M.  Alcide  d'Orbigny  had  previously  (1852),  in  his  Paleontology,  con- 
sidered all  these  "  Oligocene  "  beds  as  a  Lower  Falunian  division,  class- 
ing the  faluns  of  the  Loire  as  LTpper  Falunian.  Dr.  Sandbcrger,  in  his 

«  Abhandlungen  der  Konigl.  Acad.  der  Wissen.  zu  Berlin,  1855. 
41 


64:2  CLASSIFICATION  OF  MIOCENE 

writings  on  the  fossils  of  the  Mayence  Basin,  has  lately  pointed  out 
several  connecting  links  between  the  beds  commonly  called  Lower 
Miocene  and  the  overlying  formations  coeval  with  the  faluns  of  Tou- 
raine.  M.  Raulin,  also,  in  a  paper  just  printed  on  the  faluns  of  the  Gi- 
ronde,*  has  given  the  names  of  Middle  and  Lower  Miocene  to  the 
equivalents  of  the  Fontainebleau  and  Limburg  beds,  or  to  Professor 
Beyrich's  "  Oligocene''  strata,  the  faluns  of  Touraine  being  classed  as 
"  Upper  Miocene." 

M.  Hebert  published,  in  1855,  a  map  descriptive  of  the  areas  of  two 
tertiary  seas,  which  succeeded  each  other  in  the  Paris  Basin, — the  first 
that  of  the  Calcaire  grossier,  and  the  second,  that  of  the  Fontaiuebleau 
Sands, — showing  how  marked  is  the  want  of  coincidence  between  them  • 
a  fact  which  implies  the  occurrence  of  great  geographical  changes  in 
the  interval  of  time  between  the  two  eras  compared.  In  the  explana- 
tion of  his  map  he  gives  his  reasons  for  regarding  the  zone  of  Cerithium 
plicatum,  or  that  of  the  Fontainebleau  Sands,  as  the  most  convenient 
line  of  demarcation  between  Lower  and  Middle  tertiary,  or  between 
Eocene  and  Miocene.f  M.  Lartet,  also  a  distinguished  French  osteolo- 
gist,  whose  writings  on  fossil  mammalia  are  so  well  known,  has  favored 
me  with  his  valuable  counsel  on  this  controverted  subject ;  observing, 
that  although  the  fossil  testacea  of  the  Fontainebleau  Sands  show  a 
preponderance  of  affinities  towards  an  Eocene  fauna,  and  small  connec- 
tion with  the  faluns  of  Touraine,  yet,  on  the  other  hand,  the  freshwater 
"Calcaire  de  la  Beauce,"  immediately  overlying  the  Fontainebleau 
Sands,  and  other  lacustrine  formations  in  Auvergne  and  Central  France, 
as  well  as  the  Mayence  Basin,  cannot  be  included-  in  the  same  Eocene 
system  without  doing  violence  to  paleontological  principles.  The  group- 
ing of  the  fossil  mammalia,  he  remarks,  becomes  less  natural  by  such  an 
arrangement;  for  not  only  many  genera,  but  even  some  species,  are 
found  on  both  sides  of  the  arbitrary  line  of  demarcation  thus  drawn 
between  Eocene  and  Miocene.  The  genera  Dorcatherium,  Cainotherium, 
Anchitherium,  and  Titanomys,  for  example,  and  Rhinoceros  incisivus 
and  others,  are  made  common  to  Eocene  and  Miocene. 

Professor  Forbes,  in  his  posthumous  memoir  on  a  tertiary  formation 
of  fluvio-marine  origin  in  the  Isle  of  Wight,  J  has  observed,  that  there 
are  certain  bands  of  well-marked  fossils  so  widely  extended  as  to  indi- 
cate definite  horizons  ;  and  of  these  perhaps  the  most  constant  is  "  the 
zone  of  Cerithium  plicatum"  well-marked  among  the  Tertiaries  of 
France,  Belgium,  and  Germany,  and  equally  so  in  the  Isle  of  Wight. 
Referring  then  to  the  connection  between  this  zone  and  the  underlying 
formations,  he  continues :  "  There  is  evidently  no  break  in  this  part  of 
the  series  of  Tertiary  depositions,  and  it  would  be  harsh  and  forced  to 
place  one  portion  in  the  Eocene,  and  another  in  the  Miocene,  as  has 
been  done  by  continental  geologists.  In  the  Isle  of  Wight  we  have 

°  Actes  de  1' Academic  de  Bordeaux,  1855. 

f  Bulletin,  1855,  torn.  xii.  p.  760. 

J  Mem.  Geol.  Survey,  London,  1856,  p.  99. 


AND   EOCENE   STRATA.  643 

the  true  clue  to  their  relation  clearly  exhibited  in  unmistakable  and 
perfect  sections ;  the  importance  of  which  clue  in  its  bearing  on  conti- 
nental geology  may  be  estimated  very  highly." 

The  opinion  of  my  late  lamented  friend,  so  emphatically  expressed 
in  this  passage  in  favor  of  the  classification  which  I  formerly  adopted, 
will  convince  every  reader  that  the  old  nomenclature  might  be  defended 
by  many  cogent  arguments ;  and  some  of  these  M.  Deshayes  has  lately 
set  forth  in  the  preliminary  chapter  of  his  supplement  to  "  The  Fossil 
Shells  of  the  Paris  Basin;"*  where  he  says,  that  while,  on  the  one 
hand,  the  dissimilarity  is  enormous  between  the  fossils  of  the  Fontaine- 
bleau  Sands  and  those  of  the  faluns  of  the  Loire,  we  find  the  fauna  of 
the  former  to  be  allied  to  that  of  the  marine  beds  below  the  Paris  gyp- 
sum by  a  predominance  of  certain  genera  of  shells.  These  he  enumer- 
ates, and  his  observations  are  in  harmony  with  what  I  have  said  (p. 
184)  respecting  the  "Eocene  aspect"  of  the  testaceous  fauna  of  those 
strata  which  occupy  the  debatable  ground. 

Notwithstanding  these  and  many  other  arguments  which  might  be 
adduced  in  support  of  the  classification  formerly  advocated  by  me,  and 
given  in  my  Table  at  pp.  104-5,  I  have  come  to  the  conclusion  that  it 
will  be  more  convenient  to  draw  the  line  of  separation  in  the  pla<3e  so 
generally  adopted  in  France,  provided  that  we  always  regard  it  as  an 
arbitrary  and  purely  conventional  line, — one  which  has  no  pretensions 
to  be  founded  on  any  great  change  of  species,  still  less  on  any  general 
revolution  in  the  earth's  physical  geography  assumed  to  have  happened 
at  the  era  referred  to.  The  classification  was  originally  suggested  in 
France  by  an  accidental  break  in  the  regular  succession  of  marine 
strata,  caused  by  the  intercalation  on  the  site  of  Paris  of  certain  fresh- 
water gypseous  marls,  in  which  the  Paleothere  and  other  quadrupeds 
were  discovered.  By  these  marls  the  marine  sands  of  Beauchamp,  often 
called  the  "Sables  Moyens,"  were  separated  from  the  marine  sands  of 
Fontainebleau.  In  countries  where  no  such  interruption  occurs,  the 
series,  whether  composed  of  freshwater,  fluvio-marine,  or  marine  strata, 
will  exhibit  "  beds  of  passage"  between  Eocene  and  Miocene,  such  as 
those  of  Hempstead,  in  the  Isle  of  Wight,  or  those  recently  discovered 
in  the  Alps  by  MM.  Hebert  and  Renevier,  and  described  by  them  in  the 
Bulletin  of  the  Statistical  Society  of  the  Department  of  the  Seine 
(1854).  In  this  interesting  memoir  an  account  is  given  of  a  formation 
termed  by  the  authors  "  the  Upper  Nummulitic,"  which  occurs  in  the 
neighborhood  of  Gap,  and  in  the  Diablerets  in  Savoy,  where  the  Ceri- 
thium  plicatum  and  other  shells  usually  accompanying  it  in  the  Fon- 
tainebleau Sands  and  in  Belgium  are  abundantly  intermixed  with  spe- 
cies frequent  in  the  Gres  de  Beauchamp,  and  even  in  the  inferior  Cal- 
caire  Grossier.  Here,  therefore,  we  have  an  example,  among,  the 
highly  elevated  and  contorted  strata  of  the  Alps,  of  marine  beds  of  pas- 
sage of  the  period  under  consideration,  remarkable  for  many  reasons, 

°  Description  des  Animaux  sans  Vertebras,  &c.     Paris,  1857,  p.  17. 


644 


CLASSIFICATION  OF  MIOCENE  STRATA. 


and,  among  others,  for  the  profusion  of  nummulites  in  association  with 
shells  characteristic  of  the  Fontainebleau  Sands.  This  association  has 
obliterated  one  of  the  supposed  distinguishing  characters  of  the  beds 
above  and  below  the  gypseous  series,  for  nummulites  have  never  been 
traced  in  Belgium,  French  Flanders,  England,  or  Germany,  above  the 
zone  of  Cerithium  plicatum,  or  if  so,  in  extremely  small  numbers,  and 
as  exceptional  cases.  It  was  also  thought  by  many  geologists  that  the 
principal  upheaval  or  disturbing  movements  of  the  Alps  occurred  ex- 
actly between  the  Lower  and  Middle  Tertiary,  or  between  the  Eocene 
and  Miocene  epochs,  as  usually  defined  in  France,  whereas  the  plentiful 
occurrence  of  characteristic  "  Middle  Tertiary"  shells  in  the  Diablerets, 
proves  that  the  greatest  movements  of  the  Alps  belonged  to  an  epoch 
subsequent  to  the  establishment  of  the  Cerithium  plicatum  and  many 
contemporary  species  in  the  Tertiary  seas. 

I  am  not  yet  prepared  to  divide  the  Miocene  strata  of  Europe  into 
Upper,  Middle,  and  Lower,  although  the  time  is  not  far  distant  when 
such  a  subdivision  will  become  necessary  and  possible.  Meanwhile,  the 
following  modification  of  the  Table  at  pp.  104,  105,  is  proposed,  con- 
sisting simply  of  a  substitution  of  the  term  "Lower  Miocene"  for 
"  ^PPer  Eocene,"  and  of  a  subdivision  of  the  Middle  Eocene  of  the 
same  Table  into  two  parts. 


Proposed  Modification  of  the  Table  of  Fossiliferous  Strata, 
pp.  104-105. 


6. 


7  B. 


UPPER 
MIOCENE, 


G.     LOWER 
MIOCENE. 


7  A.    UPPER 
EOCENE. 


MIDDLE 
EOCENE. 


British  Examples. 
Wanting  in  the  British  Isle* 


Hempstead  Beds,  Isle  of  Wight, 
p.  102. 


1.  Bembridge  Beds,  Isle  of  Wight, 
p.  203. 

2.  Osborne  Series,  p.  210. 

3.  Headon  Series.    Ibid. 

4.  Barton  Clay,  p.  212. 


fl.B 

{,'v 


Bagshot  and  Bracklesham  Beds, 

p.  213. 

Wanting. 


8.  LOWER  EOCENE.      As  in  the  table,  p.  105. 


Foreign  Equivalents  and  Synonyms. 
Faluns  of  Touraine,  p.  175. 
Bolderberg  Strata  in  Belgium,  p. 

178. 
Sansans,  near  Pyrenees,  South  of 

France. 
.  Basin  of  Vienna,  p.  179. 

Ores  de  Fontainebleau,  p.  194. 

Calcaire  de  la  Beauce.    Ibid. 

Mayence  basin,  p.  190. 

Limburg  beds,  Belgium,  p.  188. 

"Oligocene"  strata  of  North  Ger- 
many. 

Nebraska  beds  in  United  States,  p. 
206. 

1.  Gypseous  Series  of  Montmartre, 

p.  223. 
2  &  3.   Calcaire  Siliceux,  p.  225 ; 

or  Travertin  inf6rienr. 
4.  Gres  de  Beauchamp,  or  Sables 

Moyens,  p.  226. 
4.  Laeken  beds,  Belgium. 

1.  Calcaire  Grossier  of  Paris  basin, 
p.  226. 

2.  Upper    Soissonnais,    Sands    of 
Cuisse-Lamotte,  p.  228. 

1  &  2.  Nummulitic  formation  of 
Europe,  Asia,  &e.,  p.  229. 


DENUDATION  OF  WEALDEN.  645 


MIOCENE    FAUNA    OF    THE    SEWALIK    HILLS,  p.  182. 

THE  genus  Dinotkerium,  so  characteristic  of  the  Falunian  or  Upper 
Miocene  period  in  Europe,  occurs  in  India  in  strata  of  the  same  age. 
But  as  yet  it  has  only  been  found  in  Perim  Island,  in  the  Gulf  of  Cam- 
bay,  and  not  among  the  fossils  of  the  Sewalik  or  Sub-Himalayan  Hills, 
as  stated  by  mistake  in  the  text  (p.  182).  Seven  species  of  Sewalik 
elephants  have  been  alluded  to,  whereas  the  number  is  in  fact  only  five, 
three  of  which  are  referred  by  Dr.  Falconer  to  the  sub-genus  Stegodon, 
comprising  forms  intermediate  between  the  Mastodon  and  Elephant. 
The  hippopotamus  mentioned  in  the  same  page  (182),  belongs  to  the 
sub-genus  Hexaprotodon,  a  form  now  extinct.  The  Anoplotherium 
posterogenium,  supposed  when  first  discovered  to  present  a  generic  link 
between  the  Sewalik  fauna  and  that  of  the  Eocene  period,  is  now  rec- 
ognized as  a  species  of  Chalicotherium  (Anisodon  of  Lartet),  a  genus  of 
pachyderms  intermediate  between  the  Rhinoceros  and  Anoplothere.  The 
same  genus  occurs  in  Miocene-  or  Falunian  strata  at  Sansan,  in  the 
department  of  Gers,  in  the  South  of  France.  Among  the  Sub-Himalayan 
fossils,  a  giraffe,  camel,  and  large  ostrich  may  be  cited  as  proofs  that 
there  were  formerly  extensive  plains  where  now  a  steep  chain  of  hills, 
with  deep  ravines,  runs  for  many  hundred  miles  east  and  west. 

Fifteen  species  of  freshwater  shells  of  the  genera  Paludina,  Melania, 
Ampullaria,  and  Unto  were  obtained  by  Sir  P.  Cautley  and  Dr.  Fal- 
coner from  the  same  strata,  and,  when  shown  by  them  in  1846  to  the 
late  Prof.  E.  Forbes,  were  pronounced  by  him  to  be  all  extinct  or  un- 
known species,  with  the  exception  of  four,  which  are  still  inhabitants  of 
Indian  rivers.  Such  a  proportion  of  living  to  extinct  species  of  Mol- 
lusca  agrees  well  with  the  usual  character  of  an  upper  Miocene  or 
Faluniau  fauna,  as  cbserved  in  Touraine,  or  in  the  basin  of  Vienna  and 
elsewhere. 


DENUDATION  OF  THE  WEALDEN.   (Ch.  XIX.  pp.  2*71,  285.) 

Denudation  of  the  Wealden — Discovery  of  the  Lower  Crag  on  the  summit  of 
the.  North  Downs  between  Folkestone  and  Dorking. 

THE  arguments  adduced  in  the  19th  chapter,  pp.  271 — 285,  to  prove 
that  the  denudation  of  the  Wealden  area  took  place  at  many  successive 
periods,  and  at  dates  widely  remote  from  each  other,  some  of  them  an- 
tecedent to  the  deposition  of  the  Lower  Eocene  strata  of  Great  Britain, 
and  others  so  late  as  the  Pliocene  epoch,  have  lately  received  an  unex- 
pected confirmation,  for  Mr.  Prestwich  has  announced  to  the  Geological 
Society  of  London  (January  21st,  1857)  the  discovery  of  marine  sands 


646  LOWER   CRAG   ON  NORTH  DOWNS. 

of  the  crag  period,  resting  on  the  summit  of  the  North  Downs  at  vari- 
ous points  between  Folkestone  and  Dorking.  These  ferruginous  sands 
include  layers  of  iron  sandstone,  and  of  quartzose  sand,  with  flint  peb- 
bles, and  occasionally  green  earth,  the  whole  deposit  resembling  pre- 
cisely in  mineral  character  the  sands  of  Diest,  in  Belgium,  -which  have 
long  been  considered  as  of  the  same  age  as  the  older  crag  of  Suffolk. 
The  same  Terebratula  grandis,  which  abounds  in  the  English  crag,  and 
in  the  sands  of  Diest ;  and  the  casts  of  Astarte,  Pyrula,  and  other  fos- 
sils, concur  with  the  mineral  character  of  the  beds  to  prove  the  con- 
temporaneous origin  of  these  British  and  Belgian  strata.  At  Paddles- 
worth,  4  miles  W.N.W.  of  Folkestone,  the  irony  sands,  above  mentioned, 
rest  on  an  older  flint  gravel,  at  an  elevation  of  between  600  and  700 
feet  above  the  sea,  and  near  the  edge  of  the  chalk  escarpment.  Some 
idea  of  their  exact  position  may  be  gained  by  the  reader  by  supposing 
them  placed  on  the  heights  marked  by  the  strong  black  line  above  fig. 
3,  in  the  woodcut  321  (p.  272  of  the  text  of  this  edition,  and  4th  edition 
p.  243),  or  he  may  suppose  the  tertiary  outlier  6,  fig.  329  (p.  282  of  this 
edition),  to  consist  of  Coralline  crag,  instead  of  being  a  mass  of  Eocene 
clay  and  sand. 

It  follows  from  such  facts,  that  although  the  first  elevation  of  the 
Wealden  took  place,  as  shown  in  the  19th  chapter,  in  the  early  Eocene, 
or  partly,  perhaps,  in  the  cretaceous  period ;  and  although  much  denu- 
dation was  then  effected,  yet  the  same  area  was  again  submerged  during 
the  Older  Pliocene  epoch.  The  latest  denudation,  therefore,  as  well  as 
the  present  escarpments,  were  brought  about  after  the  sea  had  become 
already  peopled  with  species  of  mollusca,  half  of  which  are  still  living. 
The  great  upheaval  of  land  in  the  Wealden  area,  thus  proved  to  be 
subsequent  in  date  to  the  Lower  Crag,  may,  as  Mr.  Prestwich  observes, 
help  to  explain  the  difference  observed  in  the  fauna  and  climate  of  the 
several  successive  crag  periods  (see  above,  p.  636) ;  for  we  may  now  with 
more  confidence  assume  that  the  sea  of  the  Coralline  Crag  was  open  to 
the  south,  so  that  shells  of  southern  forms  lived  in  it,  until  at  length, 
the  bed  of  th;*t  sea  having  upraised  650  or  700  feet,  all  communication 
with  warmer  latitudes  was  cut  off,  and  the  fauna  of  the  Red  Crag  ac- 
quired its  more  boreal  character. 

We  also  learn  from  these  recent  discoveries  how  impossible  it  may 
often  be  to  demonstrate  the  former  presence  of  the  sea  on  any  given  area 
by  organic  remains,  or  by  sea-beaches.  Long  and  diligent  inquiries  had 
been  made  before  the  year  1856,  for  sea  shells  of  recent  or  crag  species, 
and  for  the  signs  of  old  sea  margins  within  the  Wealden  area,  or  on 
Nos.  3,  4,  5,  6,  and  7  of  the  map  (p.  272  of  this  edition,  and  p.  242,  4th 
edition),  and  on  the  chalk  downs  and  tertiary  area  between  the  Weald 
and  the  Thames  (Nos.  1  and  2,  ib.) ;  but  in  vain,  until  at  last  a  few 
casts  of  shells  prove  incontestably  the  long  sojourn  of  the  Older  Pliocene 
sea  in  those  very  spaces.  We  must  now,  therefore,  admit  the  retreat  of 
its  waters  to  have  been  an  event  of  times  comparatively  modern.  It 
follows  that  in  many  cases  the  l£nd  may  have  sunk  and  have  emerged 


NEW   OOLITIC   MAMMALIA.  647 

again  without  retaining  on  its  surface  any  monuments  of  the  kind 
usually  demanded  as  indispensable  to  warrant  us  in  speculating  on 
marine  denudation  as  a  great  modifying  cause  in  the  physical  geography 
of  the  globe. 


NEW    FOSSIL    MAMMALIA    FROM    THE    PURBECK    OR    UPPER    OOLITIC 
STRATA    IN    DORSETSHIRE. 

Discovery  in  Dorsetshire  of  seven  or  eight  new  genera  of  Mammalia  in  the  Pur- 
beck  or  Upper  Oolite  strata — First  example  of  a  skull  of  a  Mammifer  from 
Secondary  Rocks — Insectivorous  Marsupials  and  Placentals  and  herbivorous 
Marsupials — Figures  and  descriptions — Light  thrown  on  the  Microlestes  or 
oldest  triassic  Mammifer — General  bearing  of  the  new  facts. 

IT  will  be  seen  by  the  text  (p.  457)  that  when  the  5th  edition  of  this 
work  was  published  two  years  ago,  six  species  only  of  mammalia  were 
known  in  the  whole  world  from  rocks  older  than  the  Tertiary.  The 
researches  of  36  years  had  been  required  to  bring  these  six  species  to 
light,  from  1818,  when  first  a  lower  jaw  from  the  Stonesfield  Oolite, 
found  10  years  before,  was  pronounced  by  Cuvier  to  be  mammalian, 
to  the  year  1854,  when  the  Spalacotkerium  of  Purbeck  was  described 
by  Owen. 

Figures  are  given  at  p.  341  of  two  small  molar  teeth  of  the  most  an- 
cient of  these  six  quadrupeds,  the  Microlestes  of  Plieninger,  found  in  a 
bone-bed  near  Stuttgart  usually  referred  to  the  Upper  Trias,  and  in 
which  Triassic  species  of  fish  and  reptiles  abound.  Figures  are  also 
given  of  the  fossil  lower  jaws  with  teeth  of  three  diminutive  mammalia 
obtained  from  the  inferior  oolite  of  Stonesfield  (pp.  311-12  of  the  text,  and 
368,  4th  ed.),  and  supposed  to  belong  to  insectivorous  creatures,  one  of 
them  at  least  to  a  marsupial  quadruped.  The  remains  of  a  fourth 
British  mammal,  also  consisting  of  a  lower  jaw  from  the  same  locality, 
found  by  the  Rev.  J.  B.  P.  Dennis,  and  made  known  in  September, 
1854,  is  alluded  to  in  a  note  at  p.  457.  Although  small,  it  was  con- 
siderably larger  than  the  three  species  previously  discovered,  being 
probably  about  the  size  of  a  rabbit.  Professor  Owen  imagines  it  to  have 
been  of  omnivorous  habits,  and  one  of  the  ungulate  or  hoofed  quad- 
rupeds, allied  to  certain  extinct  genera  of  the  tertiary  period,  called 
Hyracotherium,  Microtheriurn  and  Hyopotamus. 

The  discovery  in  Purbeck,  Dorsetshire,  in  1854,  of  the  Spalacotherium, 
a  small  insectivore  allied  to  the  Cape  mole,  is  mentioned  at  p.  295  and 
457,  as  the  first  example  of  a  mammifer  from  those  freshwater  strata. 
In  December  last  (1856)  Mr.  Samuel  H.  Beckles,  F.  G.  S.,  conversed 
with  me  in  London  on  the  desirability  of  quarrying  the  Middle  Purbeck 
in  Durlestone  Bay,  near  Swanage,  for  the  express  purpose  of  exploring 
the  fossil  contents  of  the  bed  in  which  Mr.  W.  R.  Brodie  had  procured 


648  NEW   SPECIES    OF    MAMMALIA 

the  Spalacotherium.  The  average  thickness  of  this  stratum  called  No. 
93,  or  the  "  dirt-bed,"  is  about  5  inches.*  It  lies  at  the  base  of  the 
middle  Purbeck,  and  consists  of  a  soft  marl,  or  calcareous  mud,  and  con- 
tains the  remains  of  a  few  insects  with  freshwater  shells  of  several  genera 
(Paludina,  Planorbis,  and  Cyclas),  and  many  reptiles.  As  the  fruit  of 
his  second  day's  excavations  (Dec.  llth)  Mr.  Beckles  sent  me  the  lower 
jaw  of  a  mammal  of  a  new  genus,  a  discovery  soon  followed  by  others 
in  rapid  succession,  so  that  at  the  end  of  three  weeks  there  were  disin- 
terred from  an  area  not  exceeding  40  feet  in  length  by  10  feet  in  width, 
the  remains  of  five  or  six  new  species  'belonging  to  three  or  four  distinct 
genera,  varying  in  size  from  that  of  a  mole  to  that  of  a  hedgehog,  be- 
sides the  entire  skeleton  of  a  crocodile,  the  shell  or  carapace  of  a  fresh- 
water tortoise,  and  some  smaller  reptiles.  While  these  investigations 
were  in  progress,  Mr.  W.  R.  Brodie  of  Swanage  kindly  forwarded  to 
me  at  my  request  the  fossils  which  he  had  been  accumulating  during 
two  years  (1855  and  1856)  from  the  same  thin  bed  in  a  contiguous  area 
no  less  limited  in  its  dimensions.  Besides  reptilian  remains,  there  were 
among  his  acquisitions  three  lower  jaws  of  three  mammalian  species, 
and  Dr.  Falconer,  who  interpreted  for  me  the  meaning  of  these  and 
other  fossils,  as  they  arrived  from  day  to  day,  called  my  attention  to  one 
slab  in  which  was  seen  the  upper  portion  of  a  skull,  consisting  of  the 
two  parietal  bones  in  a  good  state  of  preservation,  with  the  sagittal 
crest  well  marked,  as  also  the  connection  with  the  frontals  and  the  oc- 
cipital crest.  Although  the  lateral  and  basal  portions  of  this  cranium 
are  wanting,  enough  remains  to  show  that  it  agrees  with  the  ordinary 
type  of  living  warm-blooded  quadrupeds,  implying  probably  a  higher 
organization  than  that  of  such  genera  as  the  Stonesfield  Phascolotherium 
and  Amphitherium,  though  affording  no  clear  evidence  whether  the 
creature  was  placental  or  marsupial.  It  is  singular  that  this  specimen 
should  have  been  the  first  example  ever  seen  of  a  cranium,  or  indeed  of 
any  part  of  the  skeleton  of  a  mammifer  other  than  a  lower  maxillary 
bone  with  teeth,  from  rocks  more  ancient  than  the  tertiary.  It  supplied 
therefore  a  more  significant  kind  of  evidence  to  the  osteologist  than  had 
previously  been  obtained  of  the  exact  correspondence  in  structure  of 
the  mammalia  of  a  very  remote  period  with  the  higher  types  of  living 
vertebrata. 

In  the  same  slab  with  the  cranium  is  one  entire  side  of  a  lower  jaw 
of  a  quadruped,  for  which  Professor  Owen  proposes  the  generic  name 
of  Triconodon.  It  contains  eight  molars,  a  large  and  prominent  canine, 
and  one  broad  and  thick  incisor.  This  creature  must  have  been  nearly 
as  large  as  the  common  hedgehog.f 

0  This  so-called  "  dirt-bed"  is  designated  as  No.  93  both  in  the  Guide  to  the 
Geology  of  the  Isle  of  Purbeck,  by  the  Eev.  G.  H.  Austen  (1852),  and  by  the 
Rev.  0.  Fisher,  in  his  paper  on  the  Purbeck  strata.  Trans.  Carab.  Phil.  Soc., 
vol.  Ix.  (1855).  It  has  not  the  character  of  an  ancient  vegetable  soil,  as  the 
name  would  seem  to  imply. 

f  The  compressed  crowns  of  the  inferior  molars  in  this  Triconodon  have  each 


FROM   THE   PURBECK   OOLITE.  649 

Several  other  jaws  with  similar  tricuspid  teeth  of  larger  dimensions, 
found  by  Mr.  Beckles,  indicate  the  existence  of  another  species  of  Tri- 
conodon of  a  more  elongated  form,  and  about  one-third  larger  in  size. 
From  one  of  these  the  following  evidence  of  its  marsupial  character  was 
pointed  out  to  me  by  Dr.  Falconer.  1.  The  plurality  of  true  molars. 
2.  The  strong,  inflected  angular  process.  3.  (And  this  is  considered 
by  him  the  most  significant  of  all),  the  broad,  salient,  everted  rim  of 
the  ridge  which  is  decurrent  on  the  outer  side  from  the  condyle  along 
the  inferior  margin,  exactly  as  in  the  carnivorous  marsupials.  4.  The 
marked  development  of  the  mylo-hyoid  groove.  He  also  adds,  that 
these  two  species  of  Triconodon,  from  the  cutting  character  of  their 
teeth,  and  their  comparatively  formidable  canines,  together  with  the 
form  of  the  ascending  ramus,  are  more  like  small  ferine  animals  than 
mere  insectivorous  marsupials.  It  is  most  probable  that  they  fed  on 
prey  less  minute  than  insects. 

Among  the  jaws  of  many  smaller  insectivora  is  one  allied  to  the  type 
of  the  Stonesfield  Amphitherium,  but  generally  distinct.* 

The  following  observations  by  Professor  Owen,  on  the  genus  Tri- 
conodon, extracted  from  a  letter  which  I  received  from  him  January  27, 
1857,  are  not  the  less  interesting  as  having  been  written  before  the 
more  decisive  proofs  above  enumerated  of  the  marsupial  characters  of 
Triconodon  had  been  elicited  from  more  perfect  specimens  obtained 
about  a  month  later : — "  The  Purbeck  fossil  (the  smaller  Triconodon) 
is  most  nearly  allied  to  the  Stonesfield  insectivorous  genera,  and  shows 
characters  intermediate  between  Phascolotherium  and  Thylacotherium. 
The  three-coned  tooth  presents  the  same  type  as  in  the  molars  of 
these  genera,  but  the  first  and  third  cones  are  developed  to  nearer 
equality  with  the  second  or  mid-cone.  The  cingulum  in  Triconodon 
develops  the  same  front  and  back  talon.  In  the  size  of  the  canine, 
and  in  the  depth  and  other  proportions  of  the  jaw,  Triconodon  resem- 
bles Phascolotherium,  and  so  much  so  in  the  jaw-bone  characters  that 
if  one  be  marsupial  the  other  should  be;  but  I  cannot  get  a  clear 
evidence  of  the  inward  bend  of  the  angle,  or  of  its  extension  back- 
wards. 

"In  the  superior  number  of  molars,  Triconodon  resembles  Tliyla- 
cotherium,  and  also  Myrmecobius,  which,  by  the  way,  has  a  somewhat 
similar  type  of  molar  tooth.  The  above-cited  genera  and  Spalacothe- 
rium  have  enough  of  characters  in  common,  so  far  as  regards  mandible 
and  mandibular  teeth,  to  suggest  their  all  belonging  to  the  same  natural 

of  them  three  subequal  sharp-pointed  cusps,  rising  nearly  vertically  into  the 
same  longitudinal  plane,  with  basal  end  lobules,  but  without  additional  interior 
complication.  They  are  so  arranged,  in  a  continuous  and  compact  series,  as  to 
present  a  uniform  serrated  edge,  like  the  teeth  of  a  saw. — Dr.  Falconer. 

*  In  this  species  the  lower  jaw  has  an  elongated  slender  ramus,  containing  7 
uniform  back  molars  in  situ,  and  the  empty  alveoli  of  4  or  5  false  molars  in 
front,  together  with  a  prominent  laniariform  tooth.  The  dental  formula  agrees 
numerically  with  that  of  the  Amphitherium,  but  differs  from  it  in  the  double- 
rowed  and  complex  arrangement  of  the  crown-cusps. — Dr.  Falconer. 


650 


HERBIVOROUS   MARSUPIALS 


group  of  an  insectivorous  and  very  probably  marsupial  family.  The 
character  of  the  calvarium  of  Triconodon  offers  nothing  adverse  to  the 
above  views."* 

Besides  the  mammalia  above  alluded  to,  belonging  to  9  or  10  species 
and  to  5  or  6  genera,  all  of  them  insectivorous  or  predaceous,  we  are 
indebted  to  Mr.  Beckles  for  having  disentombed  (January  31, 1857,)  the 
remains  of  another  genus  exceedingly  unlike  the  rest,  the  relations  of 

J  0-.  i. 


Plagiaulax  Secklesii,  Falc. 

These  two  figures  represent  the  same  right  ramus  of  the  lower  jaw  seen  on  the  opposite  sur- 
faces of  a  split  stone,  the  two  taken  together  affording  data  for  a  complete  restoration  of  the  jaw. 

Upper  figure  (outer  side). 

a,  6,  e'.  Eight  ramus  of  lower  jaw  magnified  two  diameters,    a,  ft,  outer  side.     &,  o',  d',  e',  im- 
pression of  inner  side. 
a.  Incisor. 

?>,  c.  Line  of  vertical  fracture  behind  the  pre-molars. 
d'.  Impression  of  the  condyle  in  the  matrix. 
e'.  Impression  of  top  of  coronoid  process. 

/  Section  of  the  anterior  piece  of  the  jaw  at  the  fracture  &,  c,— CP,  inner  surface ;  y,  outer. 
The  notch  at  the  top  is  formed  by  one  of  the  sockets  of  the  double-fanged  true  molar. 
g.  Section  of  the  hinder  piece  near  &,  c;  sr,  inner;  ?/,  outer  surface. 
o'.  Broken  off  inflected  fold  of  inner  margin  buried  in  the  matrix. 
m.  Sockets  of  two  molars. 
p,  m.  Three  pre-moiars,  the  third  and  last  divided  by  a  crack. 

Lower  figure  (inner  side). 

a',  d.  Same  lower  jaw  on  the  opposite  slab  of  stone;  &,  d,  e,  inner  side;  Z>,  a',  h,  cast  and  im- 
pression of  outer  side. 
a'.  Outline  of  the  incisor  restored. 
J,  c.  Line  of  vertical  fracture. 
tl.  Condyle. 
e.  Coronoid. 

h.  Impression  on  the  matrix  of  the  three  pre-molars. 
i.  Empty  sockets  of  the  two  true  molars. 
n.  Orifice  of  dentary  canal. 

o.  Indication  of  the  raised  and  inflected  fold  of  the  posterior  inner  margin. 
k.  Third  or  largest  pre-molar,  magnified  5i  diameters,  showing  the  7  diagonal  grooves. 
/.  Corresponding  pre-molar  in  the  recent  Australian  Hypsiprymnus  Gaiinardi,  showing  the 
7  vertical  grooves,  magnified  3£  diameters. 

°  Allusion  is  here  made  to  the  crown  of  the  skull  before  mentioned  as  occur- 
ring in  the  same  slab.  In  the  text,  at  p.  295,  I  have  cited  the  opinion  given 
by  Professor  Owen  in  1854  (see  Geol.  Quart.  Journ.,  vol.  x.  p.  431),  that  the 
Spalacotherium  was  "  more  nearly  allied  to  the  placental  than  to  the  marsupial 
insectivora,"  an  opinion  which,  as  will  be  seen,  he  is  now  disposed  to  modify. 


FEOM  THE   PURBECK   OOLITE. 


651 


which  to  the  living  kangaroo-rat  were  immediately  recognized  by  Dr. 
Falconer  on  its  first  arrival  in  London.* 

No  less  than  10  species  of  the  living  genus  Hypsiprymnus,  com- 
monly called  the  kangaroo-rat,  and  referred  by  Waterhouse  to  the  Ma- 
cropodidce,  or  kangaroo  family,  inhabit  the  prairies  and  scrub-jungle  of 
Australia,  feeding  on  plants  and  gnawing  scratched-up  roots.  A  strik- 
ing peculiarity  of  their  dentition,  one  in  which  they  differ  from  all 
other  quadrupeds,  consists  in  their  having  a  single  large  pre-molar,  the 
enamel  of  which  is  furrowed  with  7  vertical  grooves  (see  ?,  fig.  1,  where 
the  pre-molar  of  the  recent  Hypsiprymnus  Gaimardi  is  represented). 

The  largest  pre-molar  in  the  fossil  genus  exhibits  in  like  manner 
seven  parallel  grooves,  producing  by  their  termination  a  similar  serrated 
edge  in  the  crown ;  but  their  direction  is  diagonal,  a  distinction,  says 
Dr.  Falconer,  which  is  "  trivial,  not  typical." 

As  these  oblique  furrows  form  so  marked  a  character  of  the  majority 
of  the  teeth,  Dr.  Falconer  has  proposed  for  the  fossil  the  generic  name 
of  Playiaulax.  The  shape  and  relative  size  of  the  incisor  a,  figs.  1 
and  2,  exhibit  a  no  less  striking  similarity  to  Hypsiprymnus.  Never- 

Fig.2. 


Plagiaulax  minor,  Falc. 
(Magnified  4  diameters.) 

All  the  teeth  in  this  specimen  are  in  place  and  well  preserved.  The  hinder  part  of  the  jaw- 
bone, with  the  ascending  ramus  and  posterior  angle,  are  broken  away. 

a,  5.  Eight  ramus  of  lower  jaw,  with  all  the  teeth  magnified  4  diameters. 

a.  Incisor  with  po'int  broken  off.    a',  impression  of  same,  showing  that  the  inner  side,  near 

the  apex  was  hollowed  out  in  a  longitudinal  direction. 

b.  Offset  of  coronoid,  the  rest  of  which  is  wanting. 
m.  The  two  true  molars. 

p,  m.  The  four  pre-molars. 

c.  The  first  molar,  magnified  8  diameters. 

Upper  figure,  the  crown.  Lower  figure,  side  view. 

d-  s-^cond  molar,  crown  and  side  view. 
e.  Straight  line  indicating  the  length  of  the  jaw,  natural  size. 

theless,  the  more  sudden  upward  curve  of  this  incisor,  especially  in 
the  larger  species,  as  well  as  the  number  and  characters  of  the  other 
teeth,  and  the  shortening  compression  and  depth  of  the  jaw,  taken 
together  with  the  backward  projection  of  the  condyle  (</,  fig.  1),  indi- 
cate a  great  deviation  in  the  form  of  Plagiaulax  from  that  of  the  living 
kangaroo-rats. 

°  All  the  information  concerning  the  natural  history,  osteology,  and  affinities 
of  Plagiaulax  given  in  the  following  pages,  is  extracted  from  a  more  detailed 
paper  by  Dr.  Falconer,  shortly  to  be  published  by  the  Geological  Society,  the 
MS.  copy  of  which  has  been  liberally  placed  at  the  author's  disposal. 


652  HERBIVOROUS  MARSUPIALS 

Our  knowledge  is  at  present  confined  to  two  specimens  of  lower 
jaws,*  evidently  referable  to  two  distinct  species,  extremely  unequal 
in  size,  and  otherwise  distinguishable.  The  largest,  P.  Bedclesii  (fig.  1), 
was  about  as  big  as  the  English  squirrel  or  the  flying  phalanger  of 
Australia  (Petaurus  Australis,  Waterhouse).  The  skeleton  of  this 
phalanger  (named  P.  macrurus,  No.  1849,  Museum  of  College  of  Sur- 
geons) measures  15  inches  in  length,  exclusive  of  the  tail,  which  is  more 
than  11  inches  long.  The  smaller  fossil  (P.  minor,  fig.  2),  having 
only  half  the  linear  dimensions  of  the  other,  was  probably  only  1-1 2th 
of  its  bulk.  To  the  geologist,  however,  it  is  perhaps  the  more  interest- 
ing of  the  two,  as  Dr.  Falconer  has  recog- 
Fig>  a  nized  in  its  two  back  molars  (c,  c?,  fig.  2)  aii 

unmistakable  resemblance  to   those    of  the 
Triassic  Microlesies  (&,  c,  fig.  3). 

Of  this  most  ancient  of  known  fossil  mam- 
malia an  account  is  given  in  the  text  at  p. 
TlL?ngef  Zm^rlSS   341»  with  ^lustrations,  among  which,  how- 
Trias  of  Wirtemburg.  ever,  there  was  LI o  figure  of  the  crown  of 

&.  Crown  of  the  smaller  molar  (b,      ,        ,  ,  ,.,.  i-i-i-i 

fig.  441,  p.  341,  of  the  text)   the  larger  molar,  which  is  now  added,  with 
c  Cro\vn  of6  larger  tooth  (6°-  442   a  new  illustration  of  the  crown  of  the  smaller 
'  e         tooth.      No  naturalist  on  the    Continent  to 

whom  I  had  previously  shown  casts  and 
drawings  of  these  teeth,  had  been  able  to  give  any  feasible  conjecture 
as  to  its  affinities.  Plieninger  considered  it  to  be  predaceons,  whence 
the  name;  others  fancied  they  saw  some  likeness  in  the  form  of  its 
grinders  to  those  of  an  omnivorous  pachyderm,  as  well  as  of  an  Insec- 
tivore ;  while  Professor  Owen,  at  once  recognizing  the  mammalian  char- 
acter of  the  double-fanged  teeth,  said  they  were  distinct  from  any  type 
known  to  him.  When  these  grinders  of  Microlestes  (fig.  3)  are  com- 
pared to  those  of  Plagiaulax  minor  (d,  c,  fig.  2),  the  reader  will  agree 
with  Dr.  Falconer,  that  "had  they  all  been  found  detached  in  the 
same  slab  they  might  have  been  taken  for  back  and  front,  or  for  upper 
and  lower  teeth  of  the  same  or  some  cognate  species,  the  essential 
characters  of  the  crown  being  identical  ;f  whereas,  had  the  last  molar 
and  last  pre-molar  of  Plagiaulax  been  found  fossil  under  similar  cir- 
cumstances, they  would  in  all  probability  have  been  taken  for  teeth  not 
merely  of  different  genera,  but  even  of  different  orders  of  mammalia." 

Two  principal  questions,  observes  Dr.  Falconer,  deserve  our  con- 
sideration with  reference  to  Plagiaulax;  namely,  first,  Was  it  mar- 

*  Three  additional  specimens  of  P.  Becklesii  have  since  arrived,  some  with 
the  two  back  molars  entire.  They  confirm  all  the  conclusions  set  forth  in  the 
following  pages,  and  especially  the  affinity  of  Plagiaulax  and  Microlestes. 

f  The  last  back  molar,  whether  of  Microlestes  or  Plagiaulax,  has  two  opposed 
longitudinal  marginal  ridges,  more  or  less  lobed  or  crenated,  and  separated  by 
a  depressed  disk.  In  the  next  or  larger  molar  of  Plagiaulax,  the  cusps  are  not 
symmetrical  on  the  two  sides,  there  being  two  on  the  inner,  and  only  one  alter- 
nating lobe  on  the  outer  ;  and  such  seems  to  have  been  the  case  in  the  larger 
imperfect  tooth  of  Microlestes  (c,  fig.  3). 


FROM   THE    PURBECK   OOLITE.  653 

supial?  secondly,  Was  it  herbivorous?  The  general  resemblance  of 
the  jaws  and  teeth  to  those  of  the  living  Kangaroo-rats  raises  at  once  a 
strong  presumption  in  favor  of  the  affirmative  on  both  these  points. 
There  is,  as  before  noticed,  a  distinct  indication  in  the  fossil  of  a  bend- 
ing inwards,  or  towards  the  observer,  of  the  posterior  inner  margin  of 
jaw  o,  fig.  1  (lower  figure),  stretching  from  the  anterior  boundary  of 
the  dentary  foramen  n.  The  significance  of  this  character  will  be  ap- 
preciated by  referring  to  what  was  said  of  such  an  inflection  in  reference 
to  the  Stonesfield  Mammalia  (p.  311,  figs.  379-381).  In  both  spe- 
cies the  true  molars  are  limited  to  two ;  yet  the  jaw  of  P.  Becklesii 
was  clearly  that  of  an  adult,  having  its  full  complement  of  teeth.  This 
is  an  unexpected  number  in  a  quadruped  inferred  to  be  marsupial,  in 
which  tribe  the  normal  number  of  molars  should  be  four.  In  both  spe- 
cies, moreover,  the  true  molars  are  dwarfed  in  size,  as  well  as  reduced 
in  number. 

In  the  Kangaroo-rat  there  is  a  single  grooved  pre-molar  and  four 
back  molars,  while  in  Plagiaulax,  the  true  molars  being  reduced  to 
two,  we  find,  as  if  in  compensation,  three  or  four  grooved  pre-molars. 
In  the  pigmy  flying  opossum  of  Australia  (Acrobata  pygmcea)  there  is 
an  analogous  development  of  pre-molars  with  a  reduction  of  the  back 
grinders  to  three ;  and  in  the  Sub-genus  Dromicia,  or  pigmy  phalanger, 
there  are  four  pre-molars,  while  the  back  molars  are  reduced  to  three. 
In  the  living  MyrmecoUus*  the  true  molars  are  greatly  in  excess  of  the 
normal  number ;  while  in  the  fossil  Plagiaulax  they  are  few  and  rudi- 
mentary, fewer  even  than  in  any  of  the  placental  herbivora.  It  is  true 
that  in  general  form  the  coronoid  (e,  fig.  1)  of  Plagiaulax  resembles 
more  that  of  the  predaceous  marsupials,  and  of  Dasyurus  especially, 
than  of  the  herbivorous  families ;  but  on  the  other  hand  it  is  less  ele- 
vated, and  its  surface  of  less  area,  than  in  the  predaceous  genera,  whether 
marsupial  or  placental. 

The  condyle  (d,  fig.  1),  which  is  well  preserved,  is  remarkable  for  its 
depressed  position, — a  character  which,  considered  apart  from  all  the 
rest,  might  have  been  taken  to  indicate  a  beast  of  prey ;  but  it  is  coun- 
terbalanced by  another  peculiarity  without  example,  so  far  as  Dr.  Fal- 
coner is  aware,  among  the  predaceous  genera,  whether  marsupial  or 
placental ;  viz.,  the  long  neck  and  horizontal  projection  of  the  condyle 
d  behind  the  coronoid  e.  The  other  leading  indications  imply  a  vege- 
table feeder ;  viz.,  the  limited  surface  and  moderate  elevation  of  the 
coronoid  above  the  plane  of  the  teeth,  the  feeble  development  of  the  in- 
flected margin,  the  absence  of  a  thick  angular  process,  the  advanced 
position  of  the  orifice  of  the  dentary  canal  (n,  fig.  1),  and  the  offset  of 
the  inflected  margin  above  it.  These  characters,  taken  in  conjunction 
with  those  of  the  teeth,  would  place  the  Plagiaulax  with  the  vegetable 
feeders ;  and  the  exceptional  position  of  the  condyle  may  be  a  special 
modification,  having  reference  to  the  abnormal  character  of  the  teeth ; 

*  A  figure  of  the  lower  jaw  of  this  quadruped  is  given  in  my  Principles  of 
Geology,  ch.  ix.  p.  138,  9th  ed. 


654  NEW  FOSSIL  MAMMALIA 

i.  £.,  the  excessive  development  of  the  pre-molars  and  the  reduced  num- 
ber and  size  of  the  true  molars. 

"  The  condyle  of  Plagiaulax,  therefore,"  observes  Falconer,  "  incul- 
cates an  emphatic  warning  against  too  much  stress  being  laid  upon  any 
single  character  in  Palseontological  determinations."  And  he  adds  that 
"  this  ancient  fossil  is  interesting  not  only  for  its  affinity  to  the  existing 
Kangaroo-rat  of  Australia,  but  also  as  seeming  to  furnish  a  crucial  test 
of  the  soundness,  in  some  respects,  of  certain  generalizations  which  have 
been  put  forward  respecting  the  order  of  the  successive  appearance  of 
mammalia  upon  the  surface  of  the  earth.  It  is  maintained  by  some 
British  palaeontologists  and  comparative  physiologists  of  high  authority, 
that,  while  there  is  no  positive  proof  of  serial  progressive  development 
from  the  lower  to  the  higher  forms,  there  is  clear  evidence  of  another 
order  of  development  or  passage,  viz.,  from  the  general  to  the  special,  as 
we  pass  from  the  oldest  tertiary  to  the  modern  period.  It  is  urged  by 
the  advocates  of  this  doctrine,  that  the  mammalia  of  the  Eocene  Period 
assimilated  more  to  the  general  archetype  and  embryonic  condition  of 
vertebrate  organization,  while  the  mammalia  of  later  times  successively 
furnish  examples  of  increasing  deviation  from  the  original  or  normal 
type  as  well  as  of  special  adaptation.  Among  other  arguments,  they  in- 
sist that  the  earliest  Eocene  mammalia,  both  herbivorous  and  carnivo- 
rous, possessed  in  most  cases  the  full  complement  of  teeth  ;  while  forms 
characteristic  of  later  times,  such  as  the  Felidce  and  Ruminantia,  are 
remarkable  for  special  suppression  of  these  organs.  If  the  generalization 
were  really  of  as  wide  an  application  as  has  been  claimed  for  it,  we  ought, 
in  every  great  family  of  the  mammalia,  to  find  evidence  of  closer  adher- 
ence to  the  archetype  the  further  we  recede  in  time.  But  so  far  is  this 
from  being  the  case,  that  Plagiaulax,  the  oldest  well-ascertained  herbiv- 
orous mammal,  presents  to  us  the  most  special  exception  to  be  met 
with  in  the  whole  range  of  marsupialia,  fossil  or  recent.  It  had  the 
smallest  number  of  true  molars  of  any  known  genus  in  that  sub-class ; 
thus  exhibiting  at  the  most  distant  end  of  the  chain  the  very  characters 
which,  under  the  influence  of  the  assumed  law,  we  ought  only  to  have 
found  in  some  type  of  existing  marsupials." 

While  the  MS.  of  these  pages  was  preparing  for  the  press  (February 
10,  1857),  part  of  the  cranium  of  a  mammal  was  received  from  Mr. 
Beckles,  comprising  the  two  superior  maxillary  bones  and  teeth,  with 
the  intermediate  palate  crushed,  of  a  small  insectivore.  On  the  right 
side  of  the  jaw  the  whole  series  of  molar  teeth  and  the  incisors  are  seen. 
The  grinders  are  more  numerous,  but  the  dental  characters,  says  Dr. 
Falconer,  bear  a  relation  to  those  of  the  insectivorous  genus  Ericulus, 
peculiar  to  Madagascar,  and  from  the  general  bearing  of  the  evidence, 
it  is  presumed  that  the  fossil  was  a  minute  Placental  Insectivore.* 

°  Although  the  teeth  differ  considerably  in  shape  from  those  of  the  other 
Purbeck  fossils,  it  is  just  possible  that  this  creature  may  be  the  same  as  some 
of  the  minuter  species  above  alluded  to,  and  known  as  yet  only  by  their  lower 
jaws. 


FROM  THE   PURBECK  OOLITE.  655 

This  was  the  first  example  of  an  upper  jaw  with  teeth  of  a  fossil  mam- 
mal obtained  from  any  secondary  rock,  and  only  five*  such  jaws  were 
procured  by  Mr.  Beckles  when  the  entire  number  found  by  him  had 
amounted  (March  20th)  to  twenty-eight.  The  other  seven  specimens 
found  at  Purbeck  by  Mr.  Brodie,  consisted  in  like  manner  of  lower  jaws ; 
and  the  same  may  be  said  of  the  ten  specimens  (belonging  to  four  spe- 
cies) of  oolitic  mammalia  hitherto  discovered  at  Stonesfield. 

That  between  forty  and  fifty  pieces  or  sides  of  lower  jaws  with  teeth 
should  have  been  found  in  oolitic  strata,  and  with  them  only  five  upper 
maxillaries,  together  with  one  portion  of  a  separate  cranium,  will  natu- 
rally excite  surprise.f  There  are  no  examples  of  an  entire  skeleton,  nor 
of  any  considerable  number  of  bones  in  juxtaposition.  In  several  por- 
tions of  the  Purbeck  matrix  there  are  detached  bones,  often  much  de- 
composed, and  fragments  of  others  apparently  mammalian ;  but,  if  all 
of  them  were  restored,  they  would  scarcely  suffice  to  complete  the  five 
skeletons  to  which  the  five  upper  maxillaries  above  alluded  to  belonged. 
As  the  average  number  of  pieces  in  each  mammalian  skeleton  is  about 
250,  there  must  be  many  thousands  of  missing  bones ;  and  when  we 
endeavor  to  account  for  their  absence,  we  are  almost  tempted  to  indulge 
in  speculations  like  those  once  suggested  to  me  by  Dr.  Buckland,  when 
he  tried  to  solve  the  enigma  in  reference  to  Stonesfield  : — "  The  corpses," 
he  said,  "  of  drowned  animals,  when  they  float  in  a  river,  distended  by 
gases  during  putrefaction,  have  often  their  lower  jaw  hanging  loose,  and 
sometimes  it  has  dropped  off.  The  rest  of  the  body  may  then  be  drifted 
elsewhere,  and  sometimes  may  be  swallowed  entire  by  a  predaceous 
reptile  or  fish,  such  as  an  ichthyosaur  or  a  shark." 

We  may  also  suppose  that  when  fish  or  other  aquatic  animals  attack 
a  decaying  carcass,  whether  it  be  floating  or  has  sunk  to  the  bottom, 
they  will  first  devour  those  parts  which  are  covered  with  flesh.  A  lower 
jaw,  consisting  of  little  else  than  bones  and  teeth,  will  be  neglected,  and 
becoming  detached,  may  be  drifted  away  by  a  current  of  moderate  ve- 
locity, and  buried  apart  from  the  other  bones  in  sand  or  mud. 

Among  the  latest  discoveries  of  Mr.  Beckles  (March  19th),  is  the  lower 
jaw  of  a  small,  adult,  predaceous  quadruped,  with  a  robust  canine  and 
only  six  molars,  differing  in  this  respect  as  well  as  in  its  other  characters, 
so  far  as  the  evidence  at  present  extends,  from  the  marsupial  type. 

The  small  average  size  of  the  species  as  yet  made  out  is  worthy  of 
notice,  the  two  largest  of  them  not  exceeding  by  more  than  a  third  the 

0  The  second  of  these  is  a  fragment  of  the  facial  part  of  the  cranium  of  Tri- 
conodon,  received  from  Mr.  Beckles,  February  18th.  It  consists  of  the  rigTit 
maxillary  bone,  containing  some  of  the  molar  teeth,  together  with  a  consider- 
able portion  of  the  palate  uncrushed. 

f  As  specimens  of  mammalia  are  arriving  weekly  from  Mr.  Beckles,  we  may 
expect  a  great  addition  to  the  number  of  individuals,  as  well  as  an  increase  in 
the  number  of  species,  before  his  labors  terminate.  To  gain  access  to  these 
treasures,  he  has  already  at  his  own  cost  removed  nearly  3000  tons'  weight  of 
stone  overlying  the  bed  No.  93. 


656  FOSSIL    MAMMALIA 

dimensions  of  the  common  hedgehog  or  the  squirrel.  On  this  subject 
Dr.  Falconer  observes,  that  in  the  Miocene  freshwater  deposit  of  Seissan, 
in  the  Department  of  Gers,  near  the  Pyrenees  (so  well  explored  by  M. 
Lartet),  there  is  a  layer  in  the  marginal  part  of  the  basin  in  which  the 
bones  of  diminutive  mammalia,  such  as  shrews  and  others,  are  mixed 
with  remains  of  frogs  in  profusion  ;  while  in  a  more  central  part  of  the 
same  basin,  entire  carcasses  of  the  Mastodon  and  other  huge  animals  oc- 
cur. In  like  manner  the  thin  layer  No.  93  in  Purbeck  may  represent 
the  shallow  margin  of  a  river,  lake,  or  lagoon,  in  the  deeper  parts  of 
which  fossil  animals  of  greater  size  may  be  preserved. 

On  a  review  of  all  the  fossils  collected  by  Messrs.  Brodie  and  Beckles,' 
including  the  original  Spalacotherium,  together  with  a  lower  jaw  be- 
longing to  the  Rev.  P.  B.  Brodie,  and  communicated  to  me  by  Prof. 
Owen,  it  appears  that  we  now  possess  (March  14th)  the  evidence  of 
about  fourteen  species  of  mammalia  from  the  Middle  Purbeck,  to  say 
nothing  of  numerous  remains  of  the  highest  osteological  interest,  respect- 
ing which  no  opinion  can  be  hazarded  until  they  have  been  studied  more 
in  detail.  They  belong  to  eight  or  nine  genera,  some  insectivorous  or 
predaceous,  others  having  affinities  as  yet  doubtful,  and  one  of  a  purely 
herbivorous  type,  allied  to  the  Kangaroo-rat  of  Australia.  Some  of  the 
predaceous  species  were  marsupial,  some  of  them,  in  the  opinion  of  Dr. 
Falconer,  probably  placental. 

As  all  of  them  have  been  obtained  from  an  area  less  than  500  square 
yards  in  extent,  and  from  a  single  stratum  not  more  than  a  few  inches 
thick,  we  may  safely  conclude  that  the  whole  lived  together  in  the  same 
region,  and  in  all  likelihood  they  constituted  a  mere  fraction  of  the 
mammalia  which  inhabited  the  lands  drained  by  one  river  and  its  tribu- 
taries. They  afford  the  first  positive  proof  as  yet  obtained  of  the  co- 
existence of  a  varied  fauna  of  the  highest  class  of  vertebrata  with  that 
ample  development  of  reptile  life  which  marks  all  the  periods  from  the 
Trias  to  the  Lower  Cretaceous  inclusive,  and  with  a  gymnospermons 
flora,  or  that  state  of  the  vegetable  kingdom  when  cycads  and  conifers 
predominated  over  all  kinds  of  plants,  except  the  ferns,  so  far  at  least 
as  our  present  imperfect  knowledge  of  fossil  botany  entitles  us  to  speak. 

The  annexed  table  will  enable  the  reader  to  see  at  a  glance  how  con- 
spicuous a  part,  numerically  considered,  the  mammalian  species  of  the 
Middle  Purbeck  now  play  when  compared  with  those  of  other  forma- 
tions more  ancient  than  the  Paris  gypsum,  and  at  the  same  time  it 
will  help  him  to  appreciate  the  enormous  hiatus  in  the  history  of  fossil 
mammalia,  which  at  present  occurs  between  the  Purbeck  and  Eocene 
Periods.* 

0  In  drawing  up  this  table  I  have  been  assisted  by  Professor  Owen,  in  refer- 
ence to  the  British,  and  by  MM.  Lartet  and  Hebert  in  reference  to  the  fossil 
mammalia  of  the  French  Eocene  strata.  There  are,  besides,  several  undescribed 
species  in  the  collection  of  the  two  last-mentioned  paleontologists,  or  in  mu- 
seums known  to  them  ;  and  in  regard  to  one  or  two  of  the  Eocene  continental 
localities  out  of  the  Paris  basin,  the  age  of  the  deposits  is  too  little  known  to 
allow  us  to  include  their  fossils  in  the  Table. 


IN   SECONDARY   ROCKS. 


657 


Number  and  Distribution  of  all  the  known  Species  of  Fossil  Mamma- 
lia from  Strata  older  than  the  Paris  Gypsum,  or  than  the  Bembridge 
Series  of  the  Isle  of  Wight. 

Headon  Series  and  Beds  between  the]  {IATT.  v  i, 
Paris  Gvpsum  and  the  Gres  de  Beau-  -}-  14  \  ™  £ngllln' 
champ.".:: J  1  Drench. 

Barton  Clay  and  Sables  de  Beauchamp ....     0 

Bagshot    Beds,    Calcaire  Grossier,   and)  fft  P? 

TERTIARY.     4      ^PP- Soissonnais  of  Cuisse-I^motte.  [  ^     (   * 

London  Clay,  including  the  Kyson  Sand . .     7     All  English. 
Plastic  Clay  and  Lignite 9J    J'gjJ^ 

Sables  de  Bracheux 1     French. f 

Thanet  Sands  and  Lower  Landenian  of  f  Q 

Belgium j 

Maestricht  Chalk 0 

White  Chalk 0 

Chalk  Marl 0 

Upper  Green  Sand 0 

Gault 0 

Lower  Green  Sand 0 

Weald  Clay,  &c 0 

Hastings  Sand 0 

Upper  Purbeck  Oolite 0 

Middle  Purbeck  Oolite 14  Eng.  (Purbeck). 

Lower  Purbeck  Oolite 0 

SECONDARY.   -!  Portland  Oolite 0 

Kimmeridge  Clay 0 

Coral  Rag 0 

Oxford  Clay 0 

Great  Oolite 4  Eng.  (Stonesfield). 

Inferior  Oolite 0 

Lias 0 

"w«™« i 

Middle 0 

Lower 0 

Permian 0 

Carboniferous 0 

PRIMARY.      i  Silurian 0 

Cambrian 0 

After  what  has  been  said  at  the  close  of  the  27th  chapter,  pp.  457, 
459,  and  at  p.  402,  ch.  xxv.,  I  have  little  to  add  in  regard  to  the  bear- 
ing of  these  discoveries  in  Purbeck  on  some  geological  theories  hastily 
embraced,  in  favor  of  the  non-existence  or  scarcity,  at  particular  periods, 
of  certain  classes  of  air-breathing  animals,  on  the  ground  of  our  not 
happening  at  present  to  have  met  with  any  fossil  representatives  of  the 
same.  It  is  worthy,  however,  of  notice,  that  in'  the  Hastings  Sands 
there  are  certain  layers  of  clay  and  sandstone  in  which  numerous  foot- 
prints  of  quadrupeds  have  been  found  by  Mr.  Beetles,  and  traced  by 

°  I  allude  to  several  Zeuglodons  found  in  Alabama,  and  referred  by  some 
zoologists  to  three  species. 

f  The  Sables  de  Bracheux,  although  somewhat  older  than  the  Plastic  clay  are 
supposed  by  Mr.  Prestwich  to  be  newer  than  the  Thanet  Sands.  They  have 
yielded  at  La  Fere  the  Arctocyon  (Palceocyori)  primcevus,  the  oldest  known  tertiary 
mammal. 

42 


658  OOLITIC   MAMMALIA. 

him  in  the  same  set  of  rocks  through  Sussex  and  the  Isle  of  Wight 
They  appear  to  belong  to  3  or  4  species  of  reptiles,  but  no  one  of  them 
to  any  warm-blooded  quadruped.  They  ought,  therefore,  to  serve  as  a 
warning  to  us,  when  we  fail  in  like  manner  to  detect  mammalian  foot- 
prints in  older  rocks  (such  as  the  New  Red  Sandstone),  to  refrain  from 
inferring  that  quadrupeds,  other  than  reptilian,  did  not  exist  or  pre-exist. 

But  the  most  instructive  lesson  read  to  us  by  the  Purbeck  strata  con- 
sists in  this : — They  are  all,  with  the  exception  of  a  few  intercalated 
brackish  and  marine  layers,  of  fresh  water-origin ;  they  are  160  feet  in 
thickness,  have  been  well  searched  by  skilful  collectors,  and  by  the  late 
Edward  Forbes  in  particular,  who  studied  them  for  months  consecu- 
tively. They  have  been  numbered,. and  the  contents  of  each  stratum 
recorded  separately,  by  the  officers  of  the  Government  Survey  of  Great 
Britain.  They  have  been  divided  into  three  distinct  groups  by  Forbes, 
each  characterized  by  the  same  genera  of  pulmoniferous  mollusca  and 
cyprides,  but  these  genera  being  represented  in  each  group  by  different 
species ;  they  have  yielded  insects  of  many  orders,  and  the  fruits  of 
several  plants ;  and  lastly,  they  contain  "  dirt  beds,"  or  old  terrestrial 
surfaces  and  soils  at  different  levels,  in  some  of  which  erect  trunks  and 
stumps  of  cycads  and  conifers,  with  their  roots  still  attached  to  them, 
are  preserved.  Yet  when  the  geologist  inquires  if  any  land  animals  of 
a  higher  grade  than  reptiles  lived  during  any  one  of  these  three  periods, 
the  rocks  are  all  silent,  save  one  thin  layer  a  few  inches  in  thickness, 
and  this  single  page  of  the  earth's  history  suddenly  reveals  to  us  in  a 
few  weeks  the  memorials  of  so  many  species  of  fossil  mammalia,  that 
they  already  outnumber  those  of  many  a  subdivision  of  the  tertiary 
series,  and  far  surpass  those  of  all  the  other  secondary  rocks  put  to- 
gether ! 

It  is  remarked  by  Professor  Owen  that  many  of  the  Purbeck  Insec- 
tivora  belong  to  the  same  natural  family  as  those  of  Stonesfield.  Some 
at  least  of  them  were  Marsupials,  and  Dr.  Falconer  has  pointed  out 
that  the  Plagiaulax  of  Purbeck,  an  herbivorous  marsupial,  was  so  much 
allied  to  the  Microlestes  of  the  Trias  as  to  lead  us  to  infer  that  that 
more  ancient  mammifer  was  likewise  a  pouched  quadruped,  having  some 
affinity  to  the  living  Kangaroo-rat. 

In  Australia  and  the  neighboring  islands  about  100  species  of  mar- 
supials exist,  together  with  a  certain  number  of  placentals  (bats  and 
rodents),  while  the  fossil  species  of  that  continent  show  that  kangaroos, 
wombats,  Tasmanian  wolves  (or  Thylacines),  dasyures,  and  other  mar- 
supials of  species  now  extinct,  preceded  the  present  creation.  Although 
the  localities  of  Stuttgardt,  Stonesfield,  and  Purbeck,  do  not  relate  to 
an  area  larger  than  the  middle  island  of  New  Zealand,  yet  there  may 
have  prevailed,  during  the  Oolitic  period,  throughout  a  much  wider 
space  in  European  latitudes,  certain  geographical  and  climatal  condi- 
tions and  a  peculiar  vegetation,  favorable  to  a  fauna  more  analogous  to 
that  of  the  present  Antipodes  than  to  that  of  modern  Europe.  During 
the  Upper  Triassic,  the  Liassic,  and  Oolitic  epochs,  one  assemblage  of 


UPPER  TRIAS   OF   EASTERN  ALPS.  659 

such  quadrupeds  may  have  succeeded  to  another,  until  at  a  later  era, 
and  after  the  interval  marked  by  the  Wealden  and  Cretaceous  rocks, 
another  and  a  different  geographical  state  of  things  being  established, 
the  tertiary  mammalia  of  Europe  entered  on  the  stage  and  occupied  the 
same  area. 

The  advocates,  however,  of  the  doctrine  of  progressive  development 
will  offer  a  different  explanation  of  the  phenomena.  They  will  refer  the 
large  admixture  of  marsupials  in  the  Stonesfield  and  Purbeck  fauna  to 
chronological  rather  than  to  climatal  conditions, — to  the  age  of  the 
planet  rather  than  to  the  state  of  a  portion  of  its  dry  land.  In  the 
Triassic  and  Oolitic  periods  they  will  say  the  time  had  not  yet  come 
for  the  creation  or  development  of  more  highly  organized  beings.  Ex- 
perience must  test  and  determine  the  soundness  of  these  theoretical 
views.  In  the  mean  while  it  may  be  useful  to  bear  in  mind  that  while 
Australia  supports  at  present  100  species  of  marsupials,  the  rest  of  the 
continents  and  islands  of  the  globe  are  tenanted  by  about  1,700  species 
of  mammalia,  of  which  only  46  are  marsupials  (namely,  the  opossums 
of  North  and  South  America),  and  in  like  manner  there  flourished  in 
the  Pliocene  period  throughout  Europe,  Asia,  and  America,  so  far  as  we 
yet  know,  a  placental  fauna,  consisting  of  species  now  for  the  most  part 
extinct,  which  was  coeval  with  the  extinct  Pliocene  marsupials  of  Aus- 
tralia. Such  facts,  although  far  to  limited  to  enable  us  to  generalize 
with  confidence,  seem  rather  to  imply  that  at  certain  periods  of  the 
past,  as  in  our  own  days,  the  predominance  of  certain  families  of  terres- 
trial mammalia  has  had  more  to  do  with  conditions  of  space  than  of 
time ;  or  in  other  words,  has  been  more  governed  by  geographical  cir- 
cumstances than  by  a  law  of  successive  development  of  higher  and 
higher  grades  of  organization,  in  proportion  as  the  planet  grew  older. 


DISCOVERY     OF     MAMMALIAN     REMAINS     IN     ROCKS    OF     HIGH    ANTIQUITY 
IN    NORTH    CAROLINA,    UNITED    STATES. 

ALTHOUGH  only  six  weeks  have  elapsed  since  the  foregoing  remarks  on 
the  Purbeck  mammals  appeared  in  the  first  edition  of  this  Supplement, 
a  remarkable  addition  has  already  been  made  during  this  short  interval 
to  our  knowledge  of  the  ancient  geographical  range  of  Secondary 
Mammalia.  Dr.  Emmons,  in  the  newly  published  volume  of  his  "Amer- 
ican Geology"  (Part  VI.  p.  93),  announces  that  last  year  (1856)  he 
met  with  three  lower  jaws  of  an  insectivorous  mammal  in  the  Chatham 
Coal-field  in  North  Carolina.  He  has  given  a  figure  of  the  outside  of 
the  ramus  of  one  of  these  jaws,  nine-tenths  of  an  inch  in  length,  con- 
taining ten  molars  in  a  continuous  series,  one  canine,  and  three  incisors. 
The  three  posterior  molars  are  tricuspid,  as  in  Spalacotkerium ;  the 
four  next,  multicuspid;  and  the  three  anterior  ones  are  simple,  conical, 


660  MARINE   UPPER  TRIAS 

and  slender.  The  incisors  are  separated,  as  in  Phascolotherium, — a 
marsupial  characteristic.  The  structural  form  of  the  jaw,  according  to 
Dr.  Emmons's  figure,  shows  some  points  of  analogy  with  Spalacotherium, 
and  some  of  difference. 

Dr.  Emmons  has  named  the  fossil  Dromatherium  sylvestre.  He  refers 
the  strata  in  which  it  was  entombed  to  the  Permian  period,  chiefly  be- 
cause they  contain  the  remains  of  Thecodont  Saurians ;  but,  as  fossil 
species  of  this  family  of  reptiles  have  been  met  with  in  the  Upper  Trias 
of  Wirtemberg,  we  cannot  lay  much  stress  on  this  argument.  This  fossil 
may  at  least  claim  an  antiquity  equal  to  that  of  the  Richmond  coal-field, 
in  Virginia,  described  in  the  text,  at  p.  330.  If  so,  the  Dromatherium 
would  belong  to  the  lower  part  of  the  Jurassic  series,  older  than  the 
Stonesfield  Slate ;  and  therefore  it  must  be  regarded  as  one  of  the  most 
ancient  representatives  of  the  mammalian  class  yet  discovered. 


UPPER  TRIAS  OF  THE  EASTERN  ALPS  (p.  333). 

Kecognition  of  a  Marine  equivalent  of  the  Upper  Trias  in  the  ATM  trian  Alps- 
True  position  of  the  St.  Cassian  and  Hallstatt  Beds— 800  new  species  of  triassic 
Mollusca  and  Radiata — Links  thus  supplied  for  connecting  the  Palaeozoic  and 
Neozoic  faunas. 

THE  true  position  in  the  series  of  certain  Alpine  rocks  called  "  the  St. 
Cassian  beds"  has  long  been  a  subject  of  doubt  and  discussion,  but  the 
researches  of  many  eminent  geologists,  among  others  MM.  Von  Buch, 
E.  de  Beaumont,  Murchison,  and  Sedgwick,  and  in  Switzerland,  MM. 
Escher  and  Merian,  and  more  lately  in  Austria,  MM.  Von  Hauer,  Suess, 
and  Homes,  have  shown  that  these  rocks  are  unquestionably  referable 
to  the  Keuper  or  Upper  Trias.  It  has  also  been  proved  that  the  Hall- 
statt beds  on  the  northern  flanks  of  the  Austrian  Alps  correspond  in  age 
with  the  St.  Cassian  beds  on  their  southern  declivity.  By  these  discov- 
eries we  become  acquainted,  suddenly  and  unexpectedly,  with  a  rich 
marine  fauna  belonging  to  a  period  previously  believed  to  be  very  barren 
of  organic  remains,  because  in  England,  France,  and  Northern  Germany, 
the  Upper  Trias  is  chiefly  represented  by  beds  of  fresh  or  brackish 
water  origin.  Mr.  Edward  Suess,  of  Vienna,  to  whom  we  are  indebted 
for  several  memoirs  on  the  rocks  in  question,  has  favored  me  with  the 
following  summary  of  the  order  of  succession  of  the  Hallstatt  beds  in 
the  Austrian  Alps,  which  I  had  an  opportunity,  when  travelling  in  the 
autumn  of  1856,  of  verifying  in  company  with  Mr.  Giimbel,  of  Munich. 

The  uppermost  strata  first .  enumerated  immediately  underlie  the 
Lower  Lias  of  the  Swabian  Jura.  This  lias  is  represented  near  Vienna 
by  a  brown  limestone,  containing  Ammonites  Bucklandi,  A.  Cony- 
bearii,  &c. 


OF  THE  AUSTRIAN  ALPS. 


661 


Infra-liassvc(?)  Strata  of  the  Austrian  Alps,  in  descending  Order. 


Koessen  beds. 

(Synonyms,  Upper  St. 
Cassian  beds  of  Escher  and 
Merian  ;  Upper  Trias  ?  or 
intermediate  between  Lias 
and  Trias  ?) 


2.  Dachstein  beds, 

between  Lias  and  Trias  ? 


3.  Hallstatt  beds 

(or  St.  Cassian). 
Trias. 


Upper  - 


Gray  and  black  limestone  with  calcareous  marls, 
having  a  thickness  of  about  50  feet.  Among 
the  fossils,  Brachiopoda  very  numerous  ;  some 
few  species  common  to  the  genuine  Lias  ;  many 
peculiar.  Avicida  contorta,  Pecten  Valwiiensis, 
Cardium  Rhceticum,  Avicula  incequivalvis,  Spirifer 
Munsteri,  Dav.  Strata  containing  the  above 
fossils  alternate  with  the  Dachstein  beds,  lying 
next  below. 

White  or  grayish  limestone,  often  in  beds  3  or  4 
feet  thick.  Total  thickness  of  the  formation 
above  2000  feet.  Upper  part  fossiliferous,  with 
some  strata  composed  of  corals.  (Lithodendron.) 
Lower  portion  without  fossils.  Among  the 
characteristic  shells  are  Hemicardium  Wulferii, 
Megalodon  triqueter,  and  other  large  bivalves. 

Red,  pink,  or  white  marble,  from  800  to  1000 
feet  in  thickness,  containing  more  than  800 
species  of  marine  fossils,  for  the  most  part  mol- 
lusca.  Many  species  of  Orthoceras.  True  Am- 
monites, besides  Ceratites  and  Goniatites,  Belemnites 
(rare),  Porcdlia,  Pleurotomaria,  Trochus,  Monotis 
salinaria,  &c. 


f  A.  Black  and  gray  limestone  "] 

4.  A.  Guttensteinbeds.        150  feet  thick,  alternating 
B.  Werfen  beds,  with  the  underlying  Wer- 

base     of     Upper  -j      fen  beds. 


Trias?    Lower  Trias 
of  some  geologists. 


B.  Red  and  green  shale  and 
sandstone  with  Salt  and 
Gypsum. 


Among  the  fossils  are 
Ceratites  cassianus,  Mya- 
citesfassaensis,  Naticella 
costata,  &c. 


In  regard  to  the  age  of  the  rocks  above  mentioned,  the  Koessen  and 
Dachstein  beds  are  referred  by  some  to  the  Lias,  by  others  to  the  Trias, 
while  many  consider  them  to  be  of  intermediate  date.  According  to 
Mr.  Suess,  the  Koessen  beds  correspond  to  the  upper  bone-bed  of  Swabia, 
in  which  the  Microlestes  was 'found  (see  p.  341),  but  it  should  not  be 
forgotten  that  that  stratum  contains  true  triassic  species  of  reptiles  and 
fish.  On  the  whole,  the  beds  1  and  2  contain  a  very  peculiar  fauna, 
and  Mr.  Suess  remarks  that  some  of  the  fossils  are  identical  with  the 
Irish  "  Portrush  beds"  of  Colonel  Portlock,  described  in  his  Report  on 
Londonderry.  The  Koessen  beds  have  been  traced  for  100  geographi- 
cal miles  from  near  Geneva  to  the  environs  of  Vienna. 

Whatever  doubts  may  be  entertained  respecting  the  exact  age  of  the 
beds  Nos.  1  and  2,  there  is  now  no  longer  any  dispute  that  the  Hallstatt 
and  St.  Cassian  beds  agree  in  age  with  the  Keuper  or  Upper  Trias ;  but 
whether  the  Werfen  sandstone,  No.  4,  should  form  part  of  the  same 
series,  or,  as  Von  Hauer  inclines  to  believe,  should  be  classed  as  the 
equivalent  of  "  the  Bunter  or  Lower  Trias,"  is  still  undetermined.  The 
absence  of  well-characterized  Muschelkalk  fossils  in  the  Austrian  Alps 
renders  this  point  very  difficult  to  decide.  Rich  deposits  of  salt,  asso- 
ciated with  the  Werfen  beds,  incline  some  geologists  to  presume  that 
they  belong  to  the  Upper  Trias.  Should  they  be  classed  as  "  Banter," 
the  Guttenstein  limestone  would  then  correspond  in  position  with  the 
Muschelkalk,  but  no  Muschelkalk  fossils  have  ever  been  met  with  in  it 


662 


ST.   CASSIAN   BEDS. 


or  in  the  Werfen ;  while,  on  the  other  hand,  the  true  Muschelkalk  is 
known  to  exist  in  the  Italian  Alps  and  in  Hungary,  so  that  all  doubts 
on  this  question  must  very  soon  be  removed. 

Among  the  800  species  of  fossils  of  the  Hallstatt  and  St.  Cassian  beds, 
many  are  still  undescribed ;  some  are  of  new  and  peculiar  genera,  as 
Scoliostoma,  fig.  4,  and  Platystoma,  fig.  5,  among  the  Gasteropoda ; 
and  Koninckia,  fig.  6,  among  the  Brachiopoda. 

Fig.  4.  Ffc.  5. 


Platystoma  Suessii, 

Hoernes. 
From  Hallstatt. 


Scoliostoma,  S.  Cassian. 
Fig.  6. 


Koninckia  Leonhardi,  Wissmann. 

a.  Dorsal  view,  natural  size. 

&.  Ventral  view,  part  of  the  converse  ventral  valve  removed  to  show  the  interior  of  dorsal 

valve  and  its  vascular  impressions.    One  of  the  spiral  processes  is  seen  through  the 

translucent  shell. 

c.  Section  of  both  valves. 

d.  Interior  of  dorsal  valve,  with  spiral  processes  restored.    (Suess.) 

The  following  table  of  genera  of  marine  shells  from  the  Hallstatt  and 
St.  Cassian  beds,  drawn  up  on  the  joint  authority  of  MM.  Suess  and 
Woodward,  shows  how  many  connecting  links  between  the  fauna  of 
primary  and  secondary  rocks  are  now  supplied  by  the  Upper  Trias. 


Genera  of  Fossil  Mollusca  in  the  St.  Cassian  and  Hallstatt  Beds. 

Characteristic  Triassic  Genera. 
Ceratites. 
Scoliostoma    (or     Coch- 

learia) . 
Naticella. 
Platystoma. 
Isoarca. 
Pleurophorus. 
Myophoria. 
Monotis. 
Koninckia. 


Common  to  Older  Rocks. 

Cyrtoceras. 

Orthoceras. 

Goniatites. 

^Loxonema. 

^Holopella. 

Murchisonia. 

Euomphalus. 

Porcellia. 

^Megalodon. 

Cyrtia. 

The  genera  marked  by  an  asterisk  are  given  on  the  authority  of  Mr.  Suess,  the 
rest  on  that  of  Mr.  Woodward  from  fossils  of  the  St.  Cassian  rocks  in  the  British 
Museum. 


Common  to  Newer  Kocks. 

Ammonites. 

°Belemnites. 

^Nerinasa. 

Opis. 

Cardita. 

Trigonia. 

Myoconchus. 

Ostrea.     1  sp. 

Plicatula. 

Thecidium. 


ANTHOLITES    OF   THE    COAL.  663 

The  first  column  marks  the  last  appearance  of  several  genera  which 
are  characteristic  of  Paleozoic  strata.  The  second  shows  those  genera 
which  are  characteristic  of  the  Upper  Trias,  either  as  peculiar  to  it  or 
as  reaching  their  maximum  of  development  at  this  era.  The  third  col- 
umn marks  the  first  appearance  of  genera  destined  to  become  more 
abundant  in  later  ages. 

As  the  Orthoceras  has  never  been  met  with  in  the  marine  Muschel- 
kalk,  much  surprise  was  naturally  felt  at  first  when  7  or  8  species  of  the 
genus  were  detected  in  the  Hallstatt  beds.  Among  them  are  some  of 
large  dimensions,  associated  with  large  Ammonites  with  foliated  lobes,  a 
form  never  seen  before  so  low  in  the  series,  while  the  orthoceras  had 
never  been  seen  so  high  ;  although  the  latter  genus  has  since  been  met 
with  in  the  Adnet,  or  Lower  Lias  strata  of  Austria.  We  can  now  no 
longer  doubt  that,  should  we  hereafter  have  an  opportunity  of  studying 
an  equally  rich  marine  fauna  of  the  age  of  the  Bunter  sandstone  or 
Lower  Trias,  the  great  discordance  between  Paleozoic  and  Neozoic  forms 
would  almost  disappear,  and  the  distance  in  time  between  the  Permian 
and  Triassic  eras  would  be  very  much  lessened  in  the  estimate  of  every 
geologist. 


ON   THE    SUPPOSED    EVIDENCE    OF    PH^ENOGAMOUS    PLANTS    (NOT    GYMNO- 
SPERMS)    IN    THE    COAL    FORMATION  (p.  37 1). 

IT  has  been  questioned  whether  hitherto  the  botanist  has  obtained 
from  strata  older  than  the  Wealden  a  single  well-determined  specimen 
of  any  flowering  plants  except  Gymnosperms,  such  as  Conifers  and  Cy- 
cads.  Hence  some  imagine  that  the  most  highly  organized  structures 
of  the  vegetable  kingdom  were  first  created  or  developed  in  geological 
periods  comparatively  modern,  although  the  antholite  of  the  coal  (of 
which  a  figure  is  given  at  p.  371)  was  classed  by  Lindley,  so  long  ago 
as  1835,  as  allied  to  the  Bromeliacese.  Mr.  Charles  Bunbury  called 
my  attention  lately  to  an  antholite  in  his  collection  from  the  Newcastle 
coal-field,  which  he  compared  to  Antholyza,  an  Irideous  genus,  and  on 
which  Dr.  Hooker,  to  whom  I  have  shown  it,  has  sent  me  the  follow- 
ing remarks. 

"Kew,  Feb.  18,  1857. 

"After  a  careful  examination  of  the  beautiful  specimen  of  Antholithes 
Pitcairnice  which  you  have  placed  in  my  hands,  I  have  no  hesitation  in 
withdrawing  the  opinion  which  I  formerly  expressed  to  you  (Manual, 
5th  ed.,  p.  371)  of  the  possible  coniferous  relation  of  the  genus  Antho- 
lithes. All  the  specimens  I  had  previously  examined  were  very  imper- 
fect, and  suggested  to  me  the  possibility  of  the  so-called  flowers  being 
tufts  of  youog  leaves  like  those  of  the  larch.  In  the  specimen  now  be- 
fore me,  these  organs  are  far  more  perfect,  and  confirm  (as  positively  as 
such  materials  can)  Lindley's  idea  that  Antholithes  is  the  spike  of  a  very 


BARRANDE'S  "  COLONIES"  IN 

highly-organized  flowering  plant  in  full  flower.  The  specimen,  as  you 
are  aware,  presents  no  structure  ;  it  is  an  impression,  and  therefore  I  can 
only  judge  of  its  possible  affinities  from  appearances.  Now,  there  is 
nothing  whatever  known  amongst  Cryptogamic  plants  having  the  most 
remote  resemblance  to  this  Antholithes,  nor  amongst  Gymnospermous 
Phsenogams,  but  there  are,  both  amongst  Monocotyledons  and  Dico- 
tyledons, genera  to  which  it  may  plausibly  be  compared.  I  allude  in 
the  former  class  to  genera  of  Bromeliacece,  Scitaminece,  and  Orchidece  ; 
in  the  latter  to  Laliatce,  Lobeliacece,  and  some  others.  Upon  the  whole, 
the  resemblance  is  strongest  to  Bromeliacece,  amongst  which  the  genus 
Pitcai'rnia  is  ranked,  and  which  suggested  the  specific  name  to  Lindley." 
Another  antholite,  apparently  of  a  different  species,  found  by  Mr. 
Prestwich  in  the  coal  strata  of  Coalbrook  Dale,  and  described  by  Mr. 
Morris  under  the  name  of  Antholites  anomalus,  is  figured  in  the  Trans- 
actions of  the  Geological  Society  of  London  (2d  ser.,  vol.  5,  pi.  xxxviii. 
fig.  5).  It  is  quite  unlike  any  thing  known  in  the  Gymnospermous  or 
Cryptogamous  classes,  and  greatly  resembles,  in  what  is  supposed  to  be 
the  evolution  of  its  floral  organs,-  the  ordinary  phsenogamous  type. 
Nevertheless,  as  both  Mr.  Robert  Brown  and  Dr.  Hooker  still  regard 
certain  terminal  appendages  belonging  to  it  as  enigmatical,  we  cannot 
declare  that  the  affinities  of  this  curious  genus  are  yet  made  out. 


SILURIAN    AND    CAMBRIAN    ROCKS,    AND    M.    BARRANDE's    THEORY 
OF    COLONIES. 

SINCE  I  alluded  in  the  text  (p.  441)  to  M.  Barrande's  discoveries  in 
Bohemia,  in  reference  to  the  Paleozoic  rocks,  I  have  enjoyed,  during 
the  summer  of  1856,  the  high  privilege  of  visiting  in  his  company  the 
field  of  his  successful  labors  near  Prague,  of  observing  the  order  and 
succession  of  the  rocks  as  interpreted  by  him,  and  of  inspecting  the  vast 
collections  which  he  has  accumulated  in  the  course  of  more  than  twenty 
years.  These  stores  are  comparable  in  number  and  importance  rather 
to  the  results  of  a  Government  survey  than  to  the  acquisitions  of  a  pri- 
vate individual.  More  than  1500  species  of  fossil  invertebrata,  previously 
unknown,  with  the  exception  of  a  few  of  the  Brachiopoda,  and  all  be- 
longing to  strata  older  than  the  Devonian, have  rewarded  his  skilful  search. 

M.  Barrande  has  shown,  in  a  recent  treatise,  that  the  fauna  called  by 
him  primordial,  a  fauna  contemporaneous  in  date  with  the  Cambrian 
rocks  of  Great  Britain,  was  also  coeval  with  the  fossils  of  the  Alum 
Schists,  and  limestones  of  Sweden,  so  well  described  by  M.  Angelin. 
In  both  countries,  this  fauna,  the  most  ancient  yet  known,  consists 
almost  exclusively  of  trilobites,  scarce  any  progress  having  yet  been 
made  in  bringing  to  light  any  mollusca  and  echinoderms  of  the  same 
period.  Enough,  however,  has  been  done  to  show  that  distinct  natural 


SILURIAN   ROCKS   OF  BOHEMIA.  665 

history  provinces  existed  at  those  very  remote  times  in  Scandinavia, 
Bohemia,  England,  and  the  United  States. 

Of  Trilobites,  27  species  have  been  found  in  Bohemia  in  these  "pri- 
mordial" beds,  71  in  Scandinavia,  12  in  America,  and  10  in  England,  all 
referable  to  the  same  group  of  genera,  but  not  one  in  a  hundred  of  the 
species  being  common  to  the  different  areas.  The  doctrine  of  the  uni- 
versality of  a  primeval  fauna,  once  so  popular,  is  thus  completely  and 
forever  overthrown.  If  it  still  lingers  in  the  minds  of  some  paleontolo- 
gists, it  is  probably  because  of  the  wide  range  of  certain  plants  of  the 
carboniferous  era.  But  besides  that  every  day  demonstrates  this  case  \o 
be  exceptional,  it  has  also  become  more  and  more  evident  that  the  appar- 
ent anomaly  is  caused  partly  by  the  predominance  in  that  ancient  flora 
of  ferns  and  Lycopodiaceae,  orders  of  which  the  living  species  are  dif 
fused  over  as  wide  a  space,  and  partly  by  the  abundance  of  plants  like 
the  Sigillariae,  of  which  there  are  no  living  analogues.  There  is  no 
proof  that  the  coniferse  of  the  carboniferous  era  had  a  more  extensive 
range  than  the  living  species  of  the  same  class. 

Not  only  in  the  earliest  known  paleozoic  epoch  has  M.  Barrande  now 
shown  that  distinct  assemblages  of  species  inhabited  separate  regions, 
but  also  that  the  same  law  prevailed  in  as  marked  a  degree  during  the 
times  of  his  second  and  third  faunas,  or  when  rocks  of  the  age  .of  the 
Lower  and  Upper  Silurian  of  England  were  formed.  At  these  periods, 
not  only  peculiar  species  of  Crustaceans,  but  Cephalopods  also,  and 
other  mollusks,  as  well  as  corals,  flourished ;  one  set  in  Bohemia,  an- 
other in  Scandinavia,  and  others  in  the  several  great  regions  before 
enumerated ;  in  a  word,  wherever  these  ancient  strata  have  been  care- 
fully studied. 

But  if  separate  portions  of  the  earth  have  at  every  former  era  been 
simultaneously  peopled  by  distinct  sets  of  marine  species,  owing  to 
variations  in  climate,  in  the  depth  of  the  sea,  the  mineral  nature  of  its 
bottom,  or  by  reason  of  the  position  of  continents  and  the  larger  islands, 
and  many  other  conditions  in  the  organic  and  inorganic  worlds,  there 
must  at  every  former  period  have  been  points  where  distinct  zoological 
provinces  were  parted  from  each  other  by  abrupt  and  narrow  barriers, 
resembling  the  Isthmus  of  Suez  or  the  Isthmus  of  Panama.  It  is  well 
known  that  a  distinct  marine  fauna  now  prevails  on  each  side  of  those 
narrow  belts  of  land,  and  it  is  evident  that  a  slight  subsidence  of  the 
earth's  crust,  to  the  amount  of  only  a  few  hundred  feet,  could  cause  one 
host  of  species  to  invade  the  territory  of  another ;  and  it  might,  there- 
fore, have  naturally  been  asked,  whether  there  are  any  signs  of  such 
invasions  having  been  effected  during  those  reiterated  upheavals  and 
subsidences  to  which  geology  bears  testimony.  M.  Barrande  has  fur- 
nished us  with  a  distinct  and  satisfactory  answer  to  this  question,  for  he 
has  detected  near  the  upper  limits  of  the  Lower  Silurian  strata  of  Bohe- 
mia (in  his  etage  D.)  an  intercalated  and  lenticular-shaped  mass  of  fos- 
siliferous  rock,  containing  organic  remains,  almost  all  of  them  specifi- 
cally identical  with  fossils  found  in  the  overlying  Upper  Silurian 


666  BARRANDE'S 

deposits.  To  this  intrusive  fauna  he  has  given  the  name  of  "  a  colony," 
a  name  somewhat  ambiguous,  perhaps,  yet  which  faithfully  expresses 
one  part  of  his  theory,  namely,  that  we  have  here  an  exemplification  of 
a  contemporaneous  fauna,  nearly  allied  to  his  third  fauna  E,  or  the 
Upper  Silurian,  which  during  the  deposition  of  the  strata  D,  obtained 
for  a  time  a  settlement  within  the  Bohemian  area,  and  was  afterwards 
expelled,  to  reappear,  after  a  lapse  of  ages,  under  a  slightly  altered 
aspect.  The  following  is  a  copy  of  the  section  by  which  M.  Barrande 
illustrates  this  doctrine  of  colonies,  which,  so  far  as  relates  to  the  geo- 
logical sequence  and  position  of  the  rocks,  I  have  verified  on  the  spot. 

Section  through  the  basin-shaped  Silurian  Strata  of  the  Centre  of 

Bohemia. — Barranfe. 

Fig.  7. 


H 

Colony 


D.  Lower  Silurian,  with  fossils  of  the  2d  fauna  of  Barrande,  coeval  with  Llandeilo  flags  of 
Murchison. 

d  1  to  d  5.  Subdivision  of  the  same. 
E  1.  Colony  or  intercalated  beds,  with  fossils  specifically  identical,  for  the  most  part,  with 

those  of  E  2. 
E2.  -j 

Q       >  Subdivisions  of  the  Upper  Silurian,  with  fossils  of  the  3d  fauna  of  Barrande, 

H.      j 

t.  Trap  of  contemporaneous  origin  with  E  2,  and  of  which  some  also  occur  in  the 
deposit  E  1. 

It  will  be  seen  that  the  colony  styled  E  by  M.  Barrande,  but  which  I  shall 
call  E  1,  occurs  in  the  midst  of  the  strata  d  4,  one  of  the  subdivisions 
of  D,  so  designated  by  Barrande.  The  fauna  proper  to  E  1  contains 
as  may  as  65  species,  five  of  them  peculiar,  or  not  known  elsewhere ; 
two  common  to  the  fauna  of  d  4,  in  which  they  are  intercalated  ;  and 
the  remaining  58  common  to  the  base  of  Barrande's  third  or  Upper 
Silurian  fauna,  which  I  have  designated  as  E  2. 

The  late  Edward  Forbes,  when  commenting  on  this  doctrine  of  colo- 
nies, observed  that  if  accepted  it  would  materially  affect  the  value  of 
the  evidence  of  organic  remains,  as  determining  the  age  and  sequence 
of  geological  formations,  since  the  proposition  involves  the  introduction 
of  a  group  of  species  that  experience  has  shown  normally  to  belong  to 
a  later  and  distinct  formation,  not  merely  among  and  mixed  with  the 
fauna  of  an  earlier  stage,  but  amid  and  separate  from  that  fauna.*  Pro- 
fessor Forbes,  therefore,  while  expressing  the  highest  admiration  of  M.  Bar- 
rande's talents  and  labors,  questions  the  accuracy  of  his  geological  facts, 
remarking  "  that  in  a  disturbed  Silurian  country  where  the  strata  lie  at 

c'  Quart.  Geol.  Journ.,  1854,  vol.  x.  p.  xxxiv. 


SILURIAN  ROCKS  OF  BOHEMIA.  667 

•very  high  angles,  and  where  there  are  probably  convolutions  and  con- 
tortions of  the  beds,  there  may  be  such  overturns  as  would  cause  the 
appearance  of  strata  containing  newer  fossils  to  lie  under  and  amid 
those  containing  older  ones."  But  had  my  late  friend  visited  the  neigh- 
borhood of  Prague,  he  would  have  learnt  that  the  strata  there  are  not  in 
a  state  of  Alpine  confusion,  and  he  would  readily  have  convinced  himself 
that  so  able  an  observer  as  M.  Barrande  had  not  been  in  any  way  deceived. 
In  fact,  the  order  of  superposition  is  not  obscure ;  and  besides,  there  is 
one  spot  in  the  suburbs  of  Prague  which  I  examined,  where  the  inter- 
calated colonial  formation  E  1  is  reduced  in  thickness  to  6  inches,  and 
where  nevertheless  it  is  quite  distinguishable  by  its  organic  contents, 
although,  as  we  might  have  anticipated,  there  occurs  here  a  slight 
blending  of  the  distinct  faunas,  two  species  of  d  4  being  associated  with 
a  great  number  of  the  characteristic  fossils  of  E  1. 

How,  then,  are  we  to  explain  the  phenomena  ?  The  facts  themselves 
seem  to  have  been  very  generally  misunderstood,  partly,  perhaps,  in  con- 
sequence of  the  use  of  the  term  "  colony ;"  partly  for  want  of  distinct 
names  for  the  two  periods,  or  subdivisions  of  time,  E  1  and  E  2.  The 
facts,  indeed,  themselves  are  by  no  means  simple,  since  they  relate,  first, 
to  the  alternate  colonization  of  a  certain  area  by  two  distinct  nations  of 
species;  secondly,  to  a  continual  change  of  character  undergone  by 
each  of  the  contemporaneous  nations,  in  consequence  of  the  dying  out 
of  old  species  and  the  births  or  first  appearances  of  new  ones.  M.  Bar- 
rande has  been  treated  very  much  as  an  antiquary  would  be  should  he 
pretend  to  have  found  monumental  evidence  of  an  Anglo-Saxon  colony 
established  on  Roman  ground  in  the  days  of  the  Emperor  Justinian ; 
whereas,  there  is  really  no  such  anachronism  in  the  paleontological 
facts,  as  exhibited  in  Bohemia,  and  as  described  by  the  author  of  the 
"  Colonial"  theory.  He  simply  tells  us,  in  regard  to  the  colony  E  1, 
that  out  of  63  species,  5  are  peculiar  to  it  where  it  is  in  its  full 
strength, — in  other  words,  there  is  a  difference  between  the  species  of 
E  1  and  pf  E  2,  amounting  to  about  8  or  9  per  cent.,  indicating  a  change  of 
no  less  than  one-twelfth  of  the  whole  fauna  in  the  interval  between  E  1 
and  E  2,  to  say  nothing  of  such  discordance  as  would  certainly  be  found 
to  exist  when  the  rarity  of  particular  species  of  the  first  period  came  to 
be  contrasted  with  their  abundance  in  E  2,  and  vice  versa. 

Before  a  geologist  is  entitled  to  regard  this  case  as  abnormal,  or  not 
in  harmony  with  the  laws  known  to  have  governed  the  fluctuations  of 
the  organic  world  in  bygone  ages,  he  must  show  that  the  fauna  called 
D  underwent  much  greater  alterations  than  did  the  fauna  of  the  mother- 
country  of  E  1  and  E  2  in  the  interval  of  time  between  the  deposit  E  1 
and  that  called  E  2,— -in  other  words,  he  ought  to  show  that  more  than 
a  twelfth  of  the  species  of  D  died  out,  and  more  than  8  or  9  in  100  of 
new  species  came  in,  in  the  interval  separating  d  4  and  d  5.  Now,  so 
far  as  I  have  learnt  from  M.  Barrande,  no  details  have  as  yet  been  ascer- 
tained respecting  the  fossils  of  these  two  subdivisions  sufficiently  minute 
to  entitle  any  one  to  infer  that  the  rate  of  fluctuation  of  the  two  faunas, 


668  ANTIQUITY  OF  FOSSIL   BIRDS. 

within  the  period  alluded  to,  was  very  unequal.  In  the  course  of  the  • 
interval  between  E  1  and  E  2,  strata  of  micaceous  shale  and  sandstone 
of  the  system  D,  more  than  3,000  feet  thick,  were  deposited ;  and  dur- 
ing the  accumulation  of  this  immense  mass  of  rock  some  species  dis- 
appeared, while  many  survived  and  are  common  to  d  4  and  d  5 ;  other 
fossils  being  peculiar  to  each  of  those  subdivisions  respectively. 

Trap  rocks  accompany  the  "  Colonial  beds"  E  1,  and  are  decidedly 
of  contemporaneous  origin.  Occasionally  an  orthoceras  may  be  seen 
involved  in  the  greenstone,  while  pebbles  and  angular  fragments  of  trap 
are  intermixed  with  the  fossils  of  the  colony. 

Again,  there  are  other  intrusions  of  similar  igneous  rocks  at  the  base 
of  E  2,  and  M.  Barrande  with  good  reason  appeals  to  these  volcanic 
appearances  as  lending  support  to  his  hypothesis  of  former  changes  of 
level,  by  which  a  barrier  of  land  may  have  been  lowered  for  a  time  so 
as  to  allow  currents  of  salt-water  flowing  from  the  northeast  to  intro- 
duce the  fauna  E  1  into  the  region  previously  occupied  by  D ;  and  a 
recurrence,  he  remarks,  of  similar  oscillations  may  afterwards  have 
caused  the  retreat  of  the  colonists,  as  well  as  the  subsequent  return  of 
most  of  them  when  the  fauna  E  2  obtained  its  permanent  footing  in 
Bohemia.  Warm  currents,  like  the  Gulf  Stream,  pouring  into  a  colder 
sea,  might  carry  with  them  a  whole  assemblage  of  species  fitted  for  a 
more  elevated  temperature,  and  capable  of  superseding  the  natives  of  a 
colder  sea,  while  colder  currents  invading  a  warmer  sea  might  give  rise 
to  analogous  phenomena.  In  each  case  along  the  edges  of  the  space 
thus  colonized,  some  members  of  the  old  native  fauna  might  maintain 
their  ground  against  the  new-comers  ;  and  this  may  explain  why,  when 
the  deposit  E  1  thins  out  to  a  few  inches,  some  species  of  D  are  inter- 
mingled with  those  of  E  1. 

It  may  be  useful  to  add  that  in  E  2  (a  calcareous  formation  only  500 
feet  in  thickness),  no  less  than  900  species  of  fossil  invertebrata  have 
been  found  by  M.  Barrande.  This  set  of  strata  passes  upwards  into  F, 
and  this  again  into  G,  and  G  into  H,  each  having,  at  the  point,  of  con- 
tact, so  many  species  in  common,  that  M.  Barrande  has  thought  it 
necessary  to  regard  the  whole  as  one  system  ;  yet  such  is  the  aggregate 
result  of  continual  changes,  that  when  the  two  extremes  of  the  series 
are  contrasted,  there  is  only  1  per  cent,  common  to  E  2  and  H. 

Many  important  conclusions  will  follow  if  we  admit  the  accuracy  of 
the  facts  and  reasonings  above  set  forth.  M.  Barrande  has  himself 
remarked,  that,  before  his  discoveries  were  made,  a  geologist,  finding  in 
some  part  of  Europe  to  the  northeast  of  Prague,  rocks  characterized  by 
the  fossils  of  E  1,  would  certainly  have  regarded  them  as  Upper  Silu- 
rian, instead  of  assigning  them  to  their  true  era,  viz.  that  of  D  or  the 
Lower  Silurian.  On  the  other  hand,  if  the  fauna  D,  after  it  was  locally 
exterminated  in  the  region  of  Prague,  still  continued  to  flourish  else- 
where under  a  slightly  modified  form  which  might,  in  accordance  with 
M.  Barrande's  nomenclature,  be  styled  d  6 — such  a  fauna  might  cer- 
tainly be  mistaken  for  one  of  Lower  Silurian  date,  although,  in  truth, 


ANTIQUITY    OF    FOSSIL   BIRDS.  669 

contemporaneous  with  strata  generally  classed  by  geologists  as  Upper 
Silurian. 

The  imagination  may  well  take  alarm  at  the  confusion  which  we  may 
expect  to  encounter  in  settling  sundry  questions  of  Geological  chronol- 
ogy, when  we  have  to  deal  with  ancient  deposits  found  on  the  frontiers 
of  distinct  Natural  History  provinces.  But  it  is  consolatory  to  reflect 
that  all  this  ambiguity  will  arise  out  of  the  strict  agreement  prevailing 
between  the  present  and  ancient  condition  of  the  globe,  and  the  laws 
governing  the  changes  of  its  surface,  whether  they  be  those  of  the  ani- 
mate or  inanimate  world.  So  long  as  we  feel  sure  that  in  existing  na- 
ture we  have  a  key  for  interpreting  the  mysteries  of  the  past,  we  need 
never  despair ;  whereas,  had  the  causes  acting  in  the  remoter  ages  differ- 
ed either  in -kind  or  degree  from  those  now  operating,  our  science  must 
forever  have  continued  one  of  mere  conjecture  and  ingenious  speculation. 


ANTIQUITY    OF    FOSSIL    BIRDS    (p.  456). 

SINCE  the  table  printed  at  p.  456  was  compiled  (in  1854),  the  records 
of  this  great  class  of  Vertebrata  can  be  carried  back  somewhat  farther 
in  time,  or  one  step  lower  down  in  the  Tertiary  series.  Early  in  1855 
the  tibia  and  femur  of  a  large  bird  equalling  at  least  the  ostrich  in  size 
were  found  at  Meudon  near  Paris,  at  the  base  of  the  Plastic  clay.  This 
bird,  to  which  the  name  of  Gastornis  Parisiensis  has  been  assigned,  ap- 
pears, from  the  Memoirs  of  MM.  Hebert,  Lartet,  and  Owen,  to  belong  to 
an  extinct  genus.  Professor  Owen  refers  it  to  the  class  of  wading  land- 
birds  rather  than  to  an  aquatic  species.* 

That  a  formation  so  much  explored  for  economical  purposes  as  the 
Argile  Plastique  around  Paris,  and  the  clays  and  sands  of  corresponding 
age  near  London,  should  never  have  afforded  any  vestige  of  a  feathered 
biped  previously  to  the  year  1855,  shows  what  diligent  search  and  what 
skill  in  osteological  interpretation  are  required  before  the  existence  of 
birds  of  remote  ages  can  be  proved  by  more  decisive  evidence  than  their 
supposed  foot-prints. 

*  Quart.  Geol.  Journ.,  vol.  xii.  p.  204,  1856. 


INDEX. 


[The  Fossils,  the  names  of  which  are  printed  in  Italics,  are  figured  in  the  volume.] 


ABICH,  M.,  on  trachytic  rocks,  467. 
Aerodus  noMlis,  tooth  of,  321. 
Acrolepis  Sedgwickii,  scale  of;  854. 
Actceon  aeutus,  great  oolite,  308. 
Actinolite-schist,  590. 
^Echmodiis,  scales  and  outline  of,  321. 
^Egean  Sea,  mud  of,  35. 

,  animal  life  in  depths  of,  136. 

^lEpiornis  of  Madagascar,  343. 

Agglomerate,  volcanic  rock,  4T1,  472. 

Agnostus  integer,  A.  rex,  450. 

Agassiz,  M.,  cited,  87,  217, 321,  349,  396, 415, 418. 

,  on  fossil  fishes  of  molasse  and  faluns,  170. 

,  on  fossil  fish  of  lias,  320. 

,  on  fossil  fish  in  Permian  marl-slate,  353. 

,  on  fish  from  Sheppey,  217. 

,  on  footprints,  348. 

,  on  fishes  of  brown-coal,  540. 

,  on  glaciers,  146, 149. 

Age,  test  of,  by  fragments  of  older  rock,  101. 
of  metamorphic  rocks,  611. 

,  test  of,  in  plutonic  rocks,  573. 

,  of  Spanish  volcanoes,  536. 

,  of  volcanic  rocks,  how  tested,  519,  522. 
Air-breathers  in  coal,  rarity  of,  401. 
Aix-la-Chapelle,  hot  springs  at,  573. 
Alabama,  cretaceous  shingle  of,  255. 
Alabaster  defined,  13. 
Alberti  on  the  Keuper,  333. 
Alexander,  Capt,  marine  sheila  in  crag  found 

by,  155. 

Alluvium,  term  explained,  79. 
. . . .,  formation  of,  81. 

in  Auvergnc,  80. 

Alpine  blocks  on  the  Jura,  148. 

erratics,  146. 

Alps,  curved  strata  of,  58. 
....,  elevated  fossiliferous  rocks  in,  4. 
....,  nummulitic  formation  of,  230. 
. . . .,  of  Switzerland,  613. 

,  Swiss  and  Savoy,  cleavage  of,  601. 

Altered  rocks,  479. 

....  by  subterranean  gases,  595. 

Alternations  of  rocks,  14 

....  of  marine  and  freshwater  formations,  32. 

Alum-schists,  Silurian,  of  Sweden,  451. 

Alumine  in  rocks,  11. 

Amllyrhynchm  cristatus  (recent)  325. 

America,  North,  Lithodomi  in  beaches  of,  78. 

. . . .,  South,  cretaceous  strata,  255. 

,  South,  fossils  of,  163. 

....,  South,  gradual  rise  of  parts  of,  46. 
Ammonites  oifrons,  A.Nodotianugyt,  A.stri- 
atulus,  A.  Walcottii,  319;  A.  Eraiken- 
ridgii,  A.  margaritatus,  A.  Stokesii,  A. 
Ktriatidus,  316;  A.  Elizabeths,  A.  Jason, 
304 ;  A.  Humphresianus,  315 ;  A.  Rhotoma- 
gensis,  251. 

Ampelite,  or  aluminous  slate,  590. 
Amphibole,  465. 

Amphibolite,  or  hornblende  rock,  472,  590. 
Amphisterjina  Ilauerina,  eocene,  179. 


Amphi&terium  Eroderipii,  jaw  o£  811. 

....  Prevostii,  jaw  of,  311. 

Amputtaria  gutuca  (recent),  30. 

Amsterdam,  or  St  Paul  Island,  508. 

Amygdaloid,  463. 

Ananchytea  ovatus,  chalk,  243. 

Ancittaria  subulata,  eocene,  31. 

Ancyloceras  gigas,  258 ;  A.  spintgerum,  251, 

Ancylm  elegans,  pleistocene,  29. 

Andolys,  chalk-cliffs  at,  268. 

Andernach,  strata  near,  540. 

Andes,  plntonic  rocks  of,  577. 

,  rocks  drifted  from,  to  Chiloe,  150. 

Andesite,  467. 

Anodonta  CordieriL  A.  latimarginatus  (re- 
cent), 28. 

Anoplotherium  commune,  tooth  of;  210. 

....  gracile,  outline  of,  225. 

Anthophyttum  lineatum,  182. 

AntholitTies,  coal,  371. 

Anthracite  in  Ehode  Island,  597. 

Anticlinal  line,  43,  57. 

Antrim  basalt,  age  of,  180. ' 

rocks  altered  by  dikes  in,  480. 

Antwerp,  strata  like  Suffolk  crag  near,  173. 

Apateon  pedestris,  a  carboniferous  reptile,  396. 

Aphanite,  or  cornean,  472. 

Apennines,  limestone  in,  478. 

Appalachian  coal-field,  389. 

Appalachians,  altered  rocks  in,  596. 

Apiocrinites  rotundus,  oolite,  806. 

Aptychus  latus,  oolite,  802. 

Apteryx  in  New  Zealand,  164. 

Apus  f  dubius,  coal,  3S5. 

Aqueous  rocks  defined,  2. 

....  rocks,  mineral  character  of,  97. 

deposits,  superposition  of,  96. 

Aralo-Caspian  formations,  175. 

Arbroath  paving-stone,  415. 

. . . .,  section  from,  to  the  Grampians,  48. 

Archegosauru*  medium,  skin  of;  A.  minor, 
coal-measures,  397. 

Archiac,  M.  d',  cited,  149. 

,  on  fossils  in  chalk,  251. 

.on  shells  in  French  lower  eocene,  228. 

Ardeche,  lava  in,  484 

Arenaceous  rocks  described,  11. 

Argillaceous  rocks,  11. 

....schist,  589. 

Argile  plastique,  or  lower  eocene,  229. 

Argyleshire,  trap-vein  in  cliff,  477. 

Argyll,  Duke  of,  on  Isle  of  Mull  tertiaries,  179. 

Arkose,  590. 

Arran,  age  of  granite  in,  583. 

section  of,  585. 

Arran,  dike  of  greenstone  in,  477. 

Arrangement  ot  fossils  in  strata,  5,  21. 

Arthur's  Seat,  altered  strata  of,  481. 

Arvicola,  tooth  of,  167. 

Asaphus  tyrannus,  lower  Silurian,  440. 

Aspidura  loricata,  Permian,  334. 

Astarte  bipartita,  A.  Omalii,  171. 


672 


INDEX. 


Astarte  borealis,  130 ;  A.  Zaurentiana,  140. 

Asterophyllitesfoliosa,  coal,  366. 

Aatrangia  lineata,  182. 

Astropecten  o'ispatus,  eocene,  218. 

Athyris  namcula,  Ayraestry,  431. 

Ashby-de-la-Zouch,  fault  in  coal-field  of,  69. 

Ascension,  lamination  of  volcanic  rocks  in,  606. 

Asti,  formations  at,  174 

Atberfield,  cretaceous  strata  of,  257. 

Atrium  of  a  volcano,  502. 

Atrypa  reticularis,  Aymestry,  434. 

Atwria  ziczac.  London  clay,  218. 

Augite,  466. 

Aulopora  serpens,  Devonian,  422. 

Auricula  (recent),  218. 

Aurillac,  freshwater  strata  of,  204. 

Austen,  Mr.  E.  A.  G.,  en  phosphate  of  lime,  251. 

. . . .,  on  upper  greensand,  250. 

Australia,  auriferous  gravel  of,  630. 

,  cave-breccias  of,  161. 

.'...,  extinct  mammals  in  auriferous  gravel  of, 

630. 

Auvergne,  freshwater  formations,  202. 
. . . .,  succession  of  changes  in,  196. 

,  lacustrine  strata,  199. 

....,  mineral  veins  of,  624. 

....,  indusial  limestone  of,  201. 

. . . .,  extinct  volcanoes  of,  545. 

. . . .,  alluvium  in,  80. 

Aveline,  Mr.,  on  Caradoc  sandstone,  438. 

Amcula  cygnipes,  A.  incequivalvis,  317. 

....  papyracea,  886 ;  A.  socialis,  334. 

Aviculopecten  sublobatus,  carboniferous,  406. 

Axinus  angulatus,  London  clay,  218. 

Aymestry  limestone,  433. 

BACILLARIA,  fossil  in  tripoli,  25. 

....  vulgaris  ?,  in  tripoli,  25. 

Baculites  anceps,  B.  faujassii,  245. 

Bagshot  sands,  214. 

Bahia  Blanca,  fossil  remains  at,  154 

Baise,  Bay  of,  strata  in,  525. 

Bakewell,  Mr.,  on  cleavage  in  the  Alps,  601. 

Bala,  lower  Silurian  rocks  at,  441. 

Balcena  emarffinata,  tympanic  bone  of,  173. 

Balgray,  near  Glasgow,  stumps  of  trees  in  coal, 

Baltic,  brackish  water  strata  on  coast  of,  119. 

Barrande,  M.,  on  Bohemian  Silurian  rocks,  441. 

,  on  primordial  fauna,  443. 

,  on  trilobites,  441. 

Barton  clay  described,  212. 

Barcombe,  chalk-flint  gravel  near,  286. 

Basilosaurus  cetoides,  233. 

Basterot,  M.  de,  on  tertiaries  of  south  of  France, 
110. 

Basalt,  6,  466. 

. . . .,  columnar,  in  the  Eifel,  485. 

,  columnar,  near  Vicenza,  484. 

. . . .,  columnar,  of  Giants'  Causeway,  6. 

....,  columnar,  structure  of,  483. 

Basset,  term  explained,  56. 

Batrachian,  eggs  of?,  in  old  red,  Scotland,  417. 

Sate,  teeth  of,  219. 

Bayfleld,  Capt.,  on  fossil  shells  in  Canada,  133. 

,  on  inland  cliffs  in  Gulf  of  St.  Lawrence,  78. 

Bean,  Mr.,  on  Norwich  crag  shells  in  York- 
shire, 155. 

on  fossil  shells  from  oolite,  314. 

Beachy  Head,  chalk-cliffs  near,  275. 

Beaumont,  M.  E.  de,  on  rocks  of  Hautes  Alpcs, 

. . . .,  on  lamination  of  volcanic  rocks,  476. 

,  on  pisolitic  limestone,  236. 

...,  on  Swiss  Alps,  579. 
....,  on  quartz,  68. 
. . . .,  on  oolite  formation  in  France,  252. 

,  on  Wealden  island,  281. 

Beck,  Dr.,  cited,  201,  242. 

. , . .,  on  graptolites,  441. 

Belemnites  hastatus,  804 ;  B.  mucronatus,  245. 

....  Puzosianus,  Oxford  clay,  305. 

Bellerophon  costatus,  carboniferous,  407. 

Belosepia  sepioidea,  eocene,  218. 


Bembridge  or  Binstead  beds,  Islo  of  "Wight, 

193,  208. 

Berenicea,  diluviana,  oolite,  307. 
Berger,  Dr.,  on  rocks  altered  by  dikes,  480 
Bergmann  on  trap,  460. 
Berlin,  tertiary  strata  near,  189. 
Bermuda  Islands,  lagoons  in,  240. 

,  rocks  of,  78. 

Bernese  Alps,  gneiss  in,  614 

Berthier,  M.,  on  augite  and  hornblende,  464 

Beudant,  M.,  on  Hungary,  544. 

Beyrich,  M.,  on  Berlin  tertiaries,  189. 

,  on  North  German  tertiaries,  178. 

Biaritz,  calcareous  cliffs  of,  72. 
Bilin  tripoli,  composed  of  Infusoria,  25. 
Binney,  Mr.,  on  Stigmaria  and  Sigillaria,  367. 
Bird,  bone  of,  in  lower  eocene  beds,  458. 
....,  footprints  of,  346. 

,  fossil,  scarcity  of,  458. 

Bischoff,  Prof.,  experiments  on  heat,  594. 

,  on  steam  at  a  high  temperature,  595. 

Blackdown  beds,  equivalent  of  gault,  251. 

Blainville,  on  number  of  genera  of  mollusca,  28. 

Boase,  Dr.,  cited,  598. 

Boblaye,  M.,  on  inland  cliffs,  73. 

....,  cited,  555. 

Bog-iron-ore,  26. 

Bohemia,  Silurian  rocks  of,  450. 

Bolderberg,  in  Belgium,  miocene  or  falunian 

strata  of,  178. 

Bone-bed  offish-remains  in  Armagh,  409. 
....,  Silurian,  431. 

Bone-beds,  usually  contain  rolled  bones,  454. 
Boom  and  Eupelmonde,  188. 
Bordeaux,  falunian  strata  near,  178. 
....,  tertiary  deposits  of,  178. 
Borrowdale,  black-lead  of,  38. 
Bosquet,  M.,  on  Kleyn  Spawen  tertiary  shells, 

134. 

. . . .,  on  Maestricht  beds,  237. 
Bos  taurus,  tooth  of,  166. 
Boston,  U.  S.,  recent  strata  in  morass,  upraised 

and  bent,  135. 

Bothnia,  Gulf  of,  land  upheaved,  45. 
Boue,  M.,  on  arrangement  of  rocks,  95. 

,  on  fossil  shells  in  Hungary,  545. 

. . . .,  on  Carrara  marble,  612. 

,  on  Swiss  Alps,  614 

Bonelli,  on  strata  in  Italy,  111. 
Boulder  formation  in  Canada,  139. 
....,  mineral  ingredients  of,  131. 
....  in  England,  126,  186. 
. . . .,  period,  fauna  of,  131. 
Boulders,  128. 

striated,  142. 

Boutigny,  M.,  cited,  565. 

Brown,  Lieut.  A.,  E.  N.,  drawings  of  rocks  in 

Gulf  of  St  Lawrence,  78. 
Bowerbank,  Mr.,  on  fossil  flora  of  Sheppey,  216. 
Bowman,  Mr.,  on  coal-seams,  391. 
Bracklesham  Bay,  characteristic  shells  of,  214. 
Bradford  encririites,  307. 
Brash,  term,  explained,  81. 
Bravard,  M.,  on  Auvergne  mammalia,  203,  421. 
Brazil,  ossiferous  caves  in,  164. 
Breccia  on  ancient  coast-lines,  73. 
Brickenden,  Captain,  on  Elgin  fossils,  413. 
Brighton,  elephant-bed  of,  287. 
Bristol,  dolomitic  conglomerate  near,  353. 

,  section  of  strata  near,  102. 

Brocchi,  on  Subapennines,  110, 173. 
Brockedon,  Mr.,  on  black-lead,  38. 
Broderip,  Mr.,  cited,  312. 
Brodie,  Eev.  P.  B.,  on  fossil  insects,  300,  327. 
. . .,  Mr.  W.  E.,  Purbeck  inammifer  found  by, 
295. 

Bromley,  oyster-bed  near,  220. 
Brcngniart,  M.  Adolphe,  on  Eocene  flora,  216. 
. . . .,  on  flora  of  cretaceous  period,  265. 

,  on  fossil  plants  in  lias,  328. 

....,  on  plants  of  bunter-sandstein,  335. 
....,  on  fossil  fir-cones,  363. 
....,  on  Permian  flora,  357. 
,  on  Sigillaria,  366. 


INDEX. 


673 


Brongniart,  M.  Adolphe,  on  asterophylites,  366. 

on  stigmaria,  367. 

,  on  age  of  acrogens,  871. 

Brongniart,  M.  Alex.,  on  Paris  tertiaries,  109. 

,  on  eocene  formation,  222. 

,  on  shells  of  numirmlitic  formation,  230. 

,  on  coal-mine  near  Lyons,  373. 

B'-ontesflabelli/er,  Devonian,  424. 

Brora,  oolitic  coal-formation,  314 

,  granite  near,  582. 

Brown-coal  of  Germany,  age  of,  180.  191. 

Brown,  Mr.  Richard,  on  stigmariae,  367. 

,  on  coal-formation,  367. 

,  on  Cape  Breton  coal-field,  380. 

,  on  carboniferous  rain-prints,  381. 

Buch,  Von.    See  Von  Buch. 

Buckland,  Dr.,  on  cave  at  Kirkdale,  160. 

,  on  coal  plants,  372. 

,  on  coprolites  in  chalk,  241. 

,  on  fish  of  lias,  321. 

,  on  glaciers  in  Caernarvonshire,  136. 

....,  on  oyster-bed  near  Bromley,  220. 

,  on  parallel  roads,  87. 

,  on  term  Poikilitic,  332. 

. . . .,  on  sanrians  of  lias,  323. 

.....  on  sudden  destruction  of  saurians,  334. 

. . . .,  cited,  161,  292,  296.  308,  309. 
Buddie,  Mr.,  on  creeps  in  coal-mines,  50. 

,  on  ancient  river-channels  of  coal-period, 

395. 

Buist,  Dr.  G.,  on  saltness  of  Red  Sea,  345. 
JBulinius  ellipticns,  209  ;  B.  lubricu.*,  30. 
Bunbury,  Mr.  C.  J.  F ,  on  plants  of  oolitic  coal- 
field, 331 ;  on  fossil  plants  in  Madeira,  515. 
Bunsen,  Prof.,  on  palagonite,  470. 
Bunter-sandstein,  335. 
Euprestis  f  elytron  of,  in  oolite,  308. 
Burmeister,  on  trilobites,  441. 
Burnes,  Sir  A.,  cited,  344 

CAIRO,  excavations  at,  3. 

Calamite*  cannceformis,  C.  Snckowii,  364. 

Calamites  near  Pictou,  375. 

Catamite,  root-end  of,  364 ;  structure  of,  365. 

Calamophyllia  radiata,  oolite,  305. 

Calamodendron,  365. 

Calcaire  grossier,  226. 

siliceux,  225. 

Calcareous  rocks,  12. 
Calcarina  rarizpina.  eocene,  227. 
Calcfola  sandalina,  Devonian,  424. 
Caldcleugh.  Mr.,  cited,  521. 
Caldera  of  Palma,  494  to  508. 
California,  auriferous  gravel  of,  629. 
Calymene  Blumenbachii,  Wenlock,  436. 
Cambrian  group,  447. 

,  lowest  fossiliferous  beds  of,  449. 

rocks  of  Sweden,  451. 

rocks  of  United  States,  451. 

volcanic  rocks,  559. 

Campagna  di  Roma,  tuffs  of,  530. 
Campdphyllum  Jlexuosum,  Devonian,  403. 
Canada,  shells  in  drift  of,  139. 
Cantal,  freshwater  formation  of,  204,  553. 

,  igneous  rocks  of,  552. 

C-pe  Breton,  coal-measures  of,  380. 

Cape  Wrath,  granite-veins  in,  568. 

Caradoc  sandstone,  437. 

Carbonaceous  shale,  812. 

Carbonate  of  lime  scarce  in  metamorphic  rocks, 

in  rocks,  how  tested,  12. 

Carboniferous  group,  35S. 
....  flora,  360,  370. 

limestone  of  North  America,  410. 

....  period,  plutonic  rocks  of,  580. 
....  period,  volcanic  rocks  of,  556. 

reptiles,  396. 

C&rcharodon  heterodon,  tooth  of,  215. 
Cardiocarpon  Ottonis,  Permian,  356. 
Cardita  glolona,  213 ;  C.  planicosta,  214. 
Cardium  porulovum,  eocene.  228. 
Cardium  dissimile.  C.  strlaiulum.  300. 
Carne,  Mr.,  on  Cornish  lodes,  621,  622. 

43 


Carrara  marble,  591,  612. 

Caryophyllia  cce&pitosa,  bed  of,  in  Sicily,  157 

Castrogiovanni,  bent  strata  near,  58. 

Catalonia,  volcanic  region  of,  531. 

Catenopora  eschar  oides,  Wenlock,  435. 

CatMus  Lamarckii,  chalk,  247. 

Canlopteris  primceva,  coal,  361. 

Cautley,  Sir  Proby,  on  Sewalik  hills,  182. 

Caves  in  Europe,  160. 

....  at  Kirkdale,  160. 

....  in  Sicily,  159. 

in  Australia,  161. 

Central  France,  Upper  Eocene  of,  194. 

Cephalaspes  Lyellii,  old  red4  415. 

Cercitites  nodosus,  triassic,  334 

Cerithium  cinctum,  30;  C.  concatum^  211. 

flegans,  C.  plicatum,  193 ;  C.  melanoide* 

220. 

Cervus  alcts,  tootn  of,  166. 

Cestracion  PhUlippi  (recent),  jaw  of,  249. 

Chalk,  or  cretaceous  beds,  236. 

,  pinnacle  of,  near  Sherringham,  134. 

of  Faxoe,  238. 

,   ..,  white,  fossils  of,  26,  245. 

,   ..,  white,  section  of,  239. 

,   . .,  white,  extent  and  origin  of,  240. 

,  white,  animal  origin  of,  241. 

.....pebbles  in,  241. 

,  difference  of,  in  North  and  South  Europe, 

252. 

cliffs,  inland,  on  Seine,  268. 

,  needles  of,  in  Normandy,  269. 

flints,  bed  of,  near  Barcombe,  2S6. 

Chama  squamosa,  eocene,  212. 
Chambers,  Mr.,  on  Glen  Roy,  88. 
Chamisso,  cited,  242. 

Chara  elaxtlca  (recent),  C.  medicaginukt,32, 

C.  tuberculata,  209. 
Chara,  in  freshwater  strata,  81. 

,  in  flints  of  Cantal,  2d5. 

,  in  Eocene  strata  of  France,  194. 

,  in  Purbeck  beds,  295. 

Charlesworth,  Mr.  E.,  on  Crag,  16S. 

,  on  Stonesfield  rnammifer,  457. 

Charpentier,  M.,  on  Alpine  glaciers,  146,  149.. 
Chtirvtherium,  footprints  of,  337,  397. 
Chelonidn,  footsteps  of,  413. 
Chemical  and  mechanical  deposits,  33. 
Chiastolite-slate,  590. 
Chili,  earthquake  in,  61. 

,  gold-mines  in,  468. 

Chiloe,  rocks  drifted  from  Andes  to,  150. 
Chimcera  monstrosa  (recent),  322. 
Chlorite-schisr,  8,  5S9. 
Christiania,  dike  near,  479. 

,  passage  of  granite  into  trap-rocks  at,  564. 

. . . .,  granite  near,  570. 

,  gneiss  near,  570. 

,  intrusion  of  granite  into  beds  near,  570. 

Chronological  groups,  102. 

table  of  fossiliferous  strata,  104. 

Cidaris  corona  ta,  coral-rag,  303. 
Cinder-bed,  Purbeck,  293. 
Cladocora  steUaria,  pliocene,  157. 
Classification  of  rocks  and  strata,  2,  10, 104. 
Claiborne,  marine  shells  of,  232. 
Clausen,  Mr.,  on  Brazil  caves,  164. 
Clausilia  biden#,  Rhine  valley,  30. 
Clavulina  corrugata,  eocene,  227. 
Clay,  defined,  11. 
Clay-slate,  8,  589. 
Clay-ironstone,  886. 
Clays,  plastic,  219. 
Cleavage  of  rocks,  601,  604. 
Climate  of  drift-period,  145. 

of  coal -period,  395. 

Clinkstone,  or  phonolite,  472. 

Clinton  group,  Silurian,  United  States,  445. 

Clyiiifn  ia  linearis,  Devonian,  421. 

Coal,  at  Brownsville,  Pennsylvania,  viow  of,  39& 

,  conversion  of  lignite,  into  394. 

. . . .,  how  formed,  372. 

,  insects  in,  335. 

measures,  353,  359. 


674 


INDEX. 


Coal  mine,  near  Lyons,  374 

,  Nova  Scotia,  time  required  for  its  growth 

383. 

,  oolitic  at  Brora,  314. 

period,  climate  of,  395. 

pipes,  danger  of,  8T3. 

seams,  continuity  of,  394. 

strata,  footprints  of  reptiles  in,  397. 

.*...,  zigzag  flexures  of,  near  Mons,  53. 
Coal-field  at  Burdiehouse,  886. 

,  oolitic,  of  Kichmond,  Virginia,  330. 

of  Ashby-de-la-Zouch,  69. 

....  of  Yorkshire,  fossils  of,  386. 

United  States,  diagram  of,  388. 

Coalbrook  Dale,  beetles  in  coal  of,  385. 

,  fossil  cones  in,  363. 

.  ..,  coal-measures  of,  S85. 

faults  in,  62. 

Cochlioduft  contoptus,  teeth  of,  409. 
Cockfield  Fell,  rocks  altered  by  dikes,  481. 
Gcelacantktts  granulatus,  scale  of,  354. 
CodorJiynchua,  sword  of,  215. 
Colchester,  Mr.,  on  mammalia  at  Kyson,  219. 
Color  in  shells  of  mountain-limestone,  406. 
Columbia,  Vinegar  Kiver  of,  224. 
Come,  ravine  in  lava  of,  550. 
Concretionary  structure,  87. 
Condensation  of  rock-material,  38. 
Gone  of  a  pine,  Purbeck,  300. 
Cones  in  Val  di  Noto,  488. 

and  craters,  461. 

....  and  craters,  absence  of,  in  England,  6. 
Conglomerate,  or  pudding-stone,  11,  47. 
....  dolomitic,  354. 
Coniferous  trees,  fossil,  368. 
Connecticut,  valley  of  the,  346. 

beds,  antiquity  of,  349. 

Conrad,  Mr.,  on  cretaceous  rocks,  255. 
Consolidation  of  strata,  33. 
Vonocephalus  striatus,  Cambrian,  450. 
Conularia  ornata,  Devonian,  423. 
Conus  deperditus,  eocene,  216. 
Conybeare,  Mr.,  cited,  64,  69,  273,  318. 

,  on  Plesiosaurus,  321. 

....,  on  oolite  and  lias,  329. 
. . . .,  on  term  Poikilitic,  332. 

on  crocodiles,  217. 

Cook,  Capt,  on  Fucus  giganteus,  242. 
Coprolites  in  chalk,  241. 
Coralline  Crag,  fossils  in,  170. 
Coral  islands  and  reefs,  34,  46. 

rag  of  oolite,  302. 

Corals,  Devonian,  geographical  distribution  of, 
428. 

of  Devonian  system,  422. 

Corals  of  Devonian  strata  in  United  States,  427. 

in  Wenlock  formation,  435. 

Corals,  neozoic  type  of,  403. 


Gorbula  alata,  Purbeck,  263. 

pisum,  eocene,  193. 

Corinth,  corrosion  of  rocks  by  gases  near,  595. 

Cornbrash  of  low«r  oolite,  805. 

Cornean,  or  aphanite,  472. 

Cornwall,  clay  in,  12;  granite-veins  in,  569, 593. 

,  mineral-veins  in,  620,  622. 

,  tin  of,  newer  than  Irish  copper,  628. 

Cotta,  Dr.  B.,  on  granite  in  Saxony,  583. 
Crag,  coralline,  fossils  in,  170. 

,  comparison  of  faluns  and,  177. 

. . . .,  fluvio-marine,  Norwich,  154 

Crags  of  Suffolk,  red  and  coralline,  110,  168. 

Craigleith  fossil  trees,  40. 

quarry,  slanting  tree  in,  376. 

Crania,  attached  to  Echinus,  23. 

Parisiensis,  chalk,  246. 

Crassatella  sulcata,  eocene,  213. 
Craw.no,  Omalii,  coralline  crag,  171. 
(•rater  of  Island  of  St.  Paul,  509. 
Creeps  in  coal-mines  described,  52. 
( Iredneria  in  quadorsandstein,  266: 
Cretaceous  rocks  of  Pyrenees,  579. 
....  group,  234 
....  group,  flora  of,  265. 


Cretaceous  strata  in  South  America  and  India, 
255. 

period,  plutonic  rocks  of,  579. 

....  volcanic  rocks,  555. 

rocks  in  United  States,  254. 

....,  lower,  256. 

Crinoids,  Silurian,  436. 

Cristellaria  rotulata,  chalk,  26. 

Crocodiles  near  Cuba,  325. 

Croizet,  M.,  on  Auvergne  fossil  mammalia,  203. 

Cromer,  contorted  drift  near,  134 

Crop  out,  term  explained,  55. 

Crust  of  earth  defined,  2. 

Crystalline  limestone,  351. 

rocks,  erroneously  termed  primitive,  9. 

rocks,  foliation  of,  606. 

schists  defined,  7. 

Curral,  valley  in  Madeira,  how  formed,  516. 

Curved  strata,  47,  49,  135. 

Cutch,  Runn  of,  844 

Cuvier,  M.,  on  eocene  formation,  222. 

,  on  Amphitherium,  311. 

. . . .,  on  tertiary  strata  near  Paris,  109. 

,  on  fossils  of  Montmartre,  223,  224. 

Cyathea  glauca  (recent),  863. 
Cyathina  Eowerbankii,  gault,  403. 
Cyathocrinites  planus,  carboniferous,  405. 
Oyathocrinus  caryocrinoides,  405. 
Cyathophyllum  flexuosum,  403 ;  C.  coespito- 

sum,  422 ;  C.  turbinatum,  435. 
Cycadeoidea  megalophylla,  Purbeck,  296. 
Gycadites  comptus,  oolite,  314. 
Cyclas  amnicd,  132 ;  C.  obovata,  28. 
Cyclopteris  Hibernica,  Devonian,  414. 
Cyclopian  Islands  in  Sicily,  523. 
Cyclostoma  elegans,  pleistocene,  30. 
Cylindrites  acutus,  oolite,  308. 
Cyprcea  coccinelloides,  red  crag,  1 70. 
Cyprides,  Lower  Purbecks,  296";  Middle  Pur- 
becks,  294;  Upper  Purbecks,  291 ;  Wealden, 
262. 

Cypridina  serrato-striata,  Devonian,  421. 
Cypris  t  inflata,  coal,  384 
Cypris  in  Lias,  327. 
....  in  Wealden,  262. 

in  marl  of  Anvergne,  199. 

....  in  Purbeck  beds,  293,  294,  296. 

Cyrena  consobrina,  28 ;  C.  cuneiformis,  220 ; 

G.  semistriata^  193. 
Cystideae  in  Silurian  rocks,  440. 
Cytheretya,  chalk,  26. 

DADOXYLON,  coal-plant,  369. 

Dana,  Mr.,  on  crystalline  limestone,  597. 

,  on  coral-reef  in  Sandwich  Islands,  241. 

,  on  volcanoes  of  Sandwich  Islands,  489, 

493,  546. 

Dapedius  monilifer,  scales  of,  321. 
Daphnogene  cinnamomifolia,  191. 
Dartmoor,  granite  of.  5SO. 
Darwin,  Mr.,  on  foliation,  606. 

,  cited,  241,  242. 

. . . .,  on  boulders  and  glaciers  in  S.  America,  142, 

. . .,  on  cleavage  in  South  America,  606. 
,  on  coral-islands  of  Pacific,  241. 

...,  on  dike  in  Bt  Helena,  528. 

,  on  habits  of  ostrich,  349. 

,  on  fossils  in  South  America,  154. 

. . .,  on  Fucus  giganteus,  242. 

. . .,  on  gradual  rise  of  part  of  S.  America,  46. 

. . . ,  on  lamination  of  volcanic  rocks,  609. 

. . .,  on  parallel  roads,  87,  88. 

. . .,  on  plutonic  rocks  of  Andes,  577. 

. . .,  on  recent  strata  near  Lima,  120. 

, . .,  on  saurians  in  Galapagos  Islands,  325. 

. . .,  on  sinking  of  coral-reefs,  46. 

...,  on  Welsh  glaciers,  136. 
Daubeny,  Dr.,  on  the  Solfatara,  595. 

. . .,  on  volcanoes  in  Auvergne,  552. 
Davidson,  Mr.,  on  liassic  spirifers,  318. 
3awson,  Mr.,  on  coal-plants,  379. 
Dax,  inland  cliff  at.  72. 
)ean,  forest  of,  coal  in,  395. 
Deane,  Dr.,  on  footprints,  347. 


INDEX. 


675 


Decken,  M.  von,  on  granite  veins  in   Corn- 
wall, 441 :  on  reptiles  in  Saarbruck  coal-field, 

396. 
De  Koninck,  M.,  cited,  184, 183. 

,  on  Kleyn  Spawen  tertiaries,  1S4. 

De  la  Becho,  Sir  H.,  cited,  293,  297,  327. 

,  on  Carrara  marbles,  612. 

,  on  clay-beds,  329. 

.  . .,  on  clay-ironstone,  3S6. 

.on  coal-measures  near  Swansea,  859. 

. . . .,  on  fossil  trees,  South  Wales,  373. 

..,  on  granite  of  Dartmoor,  593. 
. . . .,  on  mineral  veins,  623,  625,  629. 

,  on  term  supracretaceous,  103. 

.....  on  trap  of  new  red  sandstone  period, 

555. 
Delesse,  M.,  analysis  of  minerals,  475. 

,  on  basalt,  466. 

....,  on  hypersthene  rock,  473. 
. . ..,  on  hypogeno  limestone,  597. 
. . . .,  on  laterite  of  Antrim,  471. 

,  on  pyroxene,  465. 

,  on  serpentine,  474. 

Deluge,  4. 

Denudation  explained,  66. 
....  of  the  Weald  Yalley,  271. 
. . . .,  terraces  of,  in  Sicily,  75. 

,  of  volcanic  craters,  504,  507. 

Derbyshire,  lead-veins  of,  627. 
Deshayes,  M.,  identification  of  shells,  184. 
....,  on  fossil  shells  in  Hungary,  544. 
. . . .,  on  lower  eocene  shells,  223. 

,  on  tertiary  classification,  115. 

. . . .,  on  upper  marine  strata,  1S4. 
Desmarest,  on  trappean  rocks,  91. 
Desnoyers,  3tL,  on  Faluns  of  Touraine,  111. 
Desor,"M.,  on  glacial  fauna  in  Noith  America, 

139. 

Devonian  system,  term  explained,  419. 
....  series  of  North  Devon,  420. 

series  of  Eussia,  425. 

....  series  of  United  States,  426. 

De  Wael,  M.,  on  Antwerp  strata,  173. 

Diagonal,  or  cross  stratification,  16. 

DiatomacecB  in  tripoli,  25. 

Diceras  arietinum,  304. 

Dicotyledonous  leaves  in  lower  chalk,  266. 

Didelphys  Azaroe,  (recent),  jaw  of,  811. 

Didymograpsus  geminus,  D.  Murchisoni. 

442. 

Dike  in  St.  Helena.  523. 
Dikelocephalus  Jfinnenotensis,  453. 
Dikes  at  Palasonia  in  Sicily,  529. 
....  defined,  6. 

in  Scotland,  477. 

of  Somma,  526. 

,  trappean,  crystalline  in  centre,  476,  48S. 

Diluvium,  popular  explanation  of  term,  133. 

Dinornis  of  New  Zealand,  165. 

Dinotherium  gignnteum,  skull  of,  176. 

Dinothcrinm  in  India,  182. 

Diorite,  or  greenstone,  467,  472. 

Dip,  term  explained,  53. 

Diplograpsus  folium,  D.  pristis,  442. 

Dirt-bed  of  Purbeck,  297,  300. 

Dolerite,  or  greenstone,  466,  4T3. 

Dolomite  defined,  13. 

Dolomitic  conglomerate,  354. 

Domite,  or  earthy  trachyte,  473. 

Doue,  M.  B.  de,  on  volcanoes  of  Velay,  552. 

Drift,  contorted,  near  Cromer,  134. 

...  in  Ireland,  137. 

...  in  Norfolk,  132. 

...,  meteorites  in,  151. 

. . .,  northern,  in  Scotland,  130. 

. ..,  northern,  in  North  Wales,  136. 

...  of  Scandinavia,  North  Germany,  and  Eus- 
sia, 126. 

...  period,  climate  of,  145. 

. . .  period,  subsidence  in,  141. 

. . .  shells  in  Canada,  140. 
Dudley  limestone,  435. 
. . . .,  shales  of  coal  near,  593. 
Dufrenoy,  M.,  on  granite  of  Pyrenees,  593. 


Dufrenoy,  iL,  on  Hill  of  Gergovia,  558. 
Duff.  Mr.  P.,  on  reptile  of  old  red,  412. 
Dunker,  Dr.,  on  Wealden  of  Hanover,  264 
Dura  Ben,  yellow  sandstone  of,  412. 
Disaster  ringens,  inferior  oolite,  315. 

ECHIXODEKMS  of  coralline  crag,  172. 
Echinosphceriies  Balthicus,  440. 
Echinus,  with  Crania  attached,  23. 
Egerton,  Mr.,  on  fossils  of  Southern  India,  255. 
Egerton,  Sir  P.,  on  fish  of  marl-slate,  353. 

on  fossil  fish  of  Connecticut  beds,  349. 

,  on  fossils  of  Isle  of  Wight,  212. 

,  on  saurians  and  fish  in  new  red  sand- 

stone,  836. 

,  on  Ichthyosaurus,  322. 

Egg-like  bodies  in  Old  Bed  Sandstone,  417. 
Eggs,  fossil,  of  snake,  125. 
Ehrenberg,  Prof.,  on  bog-iron-ore,  26. 

,  on  infusoria,  25. 

,  on  Silurian  foraminifera,  444. 

Eifel,  volcanoes  of,  53S-543. 
Elephant-bed,  Brighton,  287. 
Elephas  primigenius,  tooth  of,  165. 
Elgin,  reptile  of  old  red,  found  near,  412. 
Elvans  of  Ireland  and  Cornwall,  629. 

,  term  explained,  5S1. 

Encrinite,  plate  of,  overgrown  with  Serpida* 

and  Sryoaoa,  307. 
Encrinite  of  Bradford,  307. 
Encrinm  liliiformis,  334. 
Eocene  foraminifera,  227. 

.  formations,  207. 

.  formations  in  England,  208.    . 

.  granite,  576. 

.  strata  in  France,  194,  222. 

.  strata  in  United  States,  231. 

.,term  defined,  115. 

.,  upper,  near  Lou  vain,  Belgium,  176. 

.  volcanic  rocks,  553. 
Eppelsheim,  Dinoiherium  of,  176, 191. 
Equisetaceae  of  coal-period,  864. 
Equisetites  columnar^,  333. 
Equisetuin  of  Virginian  oolite,  331. 

giganteum  of  S.  America,  recent,  364. 

Equus  cdballits,  tooth  of,  166. 
Erman  on  meteoric  iron  in  Eussia,  151. 
Erratics,  Alpine,  146. 

,  northern  origin  o£  128. 

Eschara  disticha,  chalk,  248. 
Eschar ina  oceani,  chalk,  248. 
Escher,  M.,  on  boulders  of  Jura,  149. 
Estheria  f,  Eichmond,  U.  S.,  331. 
Etna,  deposits  of,  523. 
Eunomia  radiata,  306. 
EuompTMltts  pentagulatus,  407. 
Euphotide,  473. 
Eurite,  564,  590. 

Euritic  porphyry  described,  462. 
Eactracrinus  JBriareus,  lias,  821. 

F  ALTOS  of  Touraine,  111,  175. 
Faluns,  comparison  of,  and  crag,  1T7. 
Falunian  type,  distinctness  o£  from  Eocene, 

179. 

Falconer,  Dr.,  on  Sewalik  Hills,  182. 
Falkland  Islands,  83. 
Farnham,  phosphate  of  lime  near,  251. 
Fascicularia  aurantium,  171. 
Fault,  term  explained,  62. 
Faults,  origin  of,  64. 
Favosites  Gothlandica,  435 ;  F.  polymorpha^ 

422. 

Faxoe,  chalk  of,  238. 
Felis  tigris,  tooth  of,  167. 
Felixstow,  remains  of  cetacea  found  near,  173. 
Felspar,  varieties  of,  453. 
Fenestella  retiformis,  352. 
Ferns  in  coal-measures,  361. 
Fife,  altered  rock  ip,  481. 
Fifeshire,  trap-dike  in,  557. 
Fish,  oldest,  in  Upper  Ludlow,  481. 
Fishes,  fossil,  of  Upper  Cretaceous,  249. 
of  Brown-coal,  540. 


676 


INDEX. 


Pishes  of  Old  Eed  Sandstone,  415. 

....  of  Wealden,  262. 

Fissures  filled  with  metallic  matter,  C21.  See 
Mineral  veins. 

Fitton,  Dr.,  on  lower  cretaceous  beds,  256. 

....,  cited,  260,  293,  297,  303. 

Fleming,  Dr.,  on  scales  offish  in  old  red,  414. 

,  on  trap-rocks  in  coal-field  of  Forth,  556. 

,  on  trap-dike  in  Fifeshire,  557. 

Flints  of  chalk,  11,  243. 

Flora,  carboniferous,  360. 

....,  cretaceous,  265. 

....  of  London  clay,  216. 

,  permian,  356. 

Flotz,  term  explained,  90. 

Flysch,  explanation  of  term,  231. 

Foliation,  term  defined,  606.' 

Fontainebleau,  Gres  de,  184, 194 

Footprint  of  bird,  347. 

Footprints  of  reptiles,  337,  847,  398,  899,  413. 

Foraminifera,  chalk,  26;  tertiary,  179,  215, 
227,  230,  231 ;  paleozoic,  409,  444. 

Forbes,  Mr.  David,  on  foliation,  607. 

Forbes,  Prof.  E.,  on  Bembridge  series,  185, 
187. 

„ . . .,  on  Caradoc  sandstone,  438. 

,...,  onCystidese,  489. 

,...,  on  Hempstead,  Isle  of  Wight  series,  185, 
192. 

....,  on  Mull  leaf -bed,  180. 

, . . .,  on  shells  in  crag  deposits,  172. 

....,  on  cretaceous  fossil  shells,  254. 

. . . .,  on  fossils  of  the  faluns,  176. 

,  on  fossils  in  drift  in  South  Ireland,  137. 

. . . .,  on  deep-sea  origin  of  Silurian  strata,  455. 

. . . .,  on  echinoderms  of  coralline  crag,  172. 

,  on  fauna  of  boulder-period,  131. 

....,  on  migrations  of  mollusca  in  glacial-pe- 
riod, 172. 

,...,on  fossils  of  Purbeck  group,  293,  297, 

. . . .,  on  strata  at  Atherfleld,  257. 

,  on  volcanic  rocks  of  oolite  period,  555. 

....,  on  depth  of  animal  life  in  ^Egean,  35, 

143. 

. . . .,  on  geographical  provinces,  256. 
Forbes,  Prof.  James,  on  zones  in  glacier-ice, 

606. 

....,  on  the  Alps,  149. 
Forchhammer,  on  scratched  limestone,  127. 
Forest,  fossil,  in  Norfolk.  133, 136. 
Forest  marble  of  oolite,  305. 
Forfarshire,  old  red  sandstone  in,  598. 
Formation,  term  defined,  3. 
Fossil  ferns  in  carbonaceous  shale,  314 
....  footsteps,  335,  837,  338. 

forest  in  Isle  of  Portland,  297. 

forest  in  Nova  Scotia,  376. 

forest  near  Wolverhampton,  374 

plants  in  wealden,  264 

remains  in  caves,  159. 

shells  from  Etna,  523;  near  Grignon,  226. 

....  shells  of  Mayence  strata,  190 ;  of  Virginia, 

181. 

....  shells,  passim. 
. . . .,  term  defined,  4 
....  trees  erect,  872. 
....  wood,  perforated  by  Teredina,  24 

wood,  petrifaction  of,  39. 

Fossils,  arrangement  of,  in  strata,  5. 
. . . . ,  freshwater  and  marine,  27. 

in  chalk  at  Faxoe,  238. 

in  falnns  of  Touraine,  176. 

....  of  chalk  and  greensand,  245,  247. 

of  Connecticut  beds,  349. 

....  of  coralline  crag,  171. 

....  of  devonian  system,  421. 

....  of  eocene  strata  in  United  States,  232, 

238. 

....of  Isle  of  Wight,  208. 
....  of  lias,  817,  328. 
....  of  London  clay,  218. 
....  of  lower  greensand,  258. 

. .  of  Ludlow  formation,  484 


Fossils  of  Maestricht  beds,  237. 
....  of  mountain  limestone,  403. 
....  of  new  red  sandstone,  333,  886. 

of  old  red  sandstone.  415. 

....of  oolite,  265,  301,  308. 

of  Permian  limestone,  353,  355. 

....  of  Purbeck,  293. 

....  of  red  crag,  170. 

....  of  Richmond,  IT.  S.,  strata,  881. 

....  of  Solenhofen,  302. 

....  of  upper  greensand,  251. 

....  of  wealden,  261. 

,  petrifaction  of,  39-43. 

. . . .,  test  of  the  age  of  formations,  97. 
Fossiliferous  strata,  tabular  view  of,  456. 
Fournet,  M.,  on  mineral  veins  of  Auvergne, 

624 

....,  on  disintegration  of  rocks,  594. 
....,  on  quartz,  563. 

Fox,  Mr.  E.  W.,  627,  on  Cornish  loes,  628. 
Fox,  Eev.  Mr.,  on  extinct  quadrupeds  of  Isle 

of  Wisht,  209. 

Freshwater  beds  of  Isle  of  Wight,  208. 
....  deposits  in  valley  of  Thames,  152. 

,  land-shells  numerous  in,  27. 

Freshwater  formations  of  Auvergne,  197. 
Freshwater  formations,  how  distinguished  from 

marine.  27,  28,  30,  82. 

associated  with  Norfolk  drift,  132. 

Freshwater  shells  in  brown-coal  near  Bonn, 

539. 

Fucus  vesiculosus,  33,  242. 
Fiilgur  canaliciilatus,  1S1. 
Fuller's  earth  of  oolite,  314. 
Fuudy,  Bay  of,  impressions  in  red  mud  of, 

346. 

Fungia  patellaris  (recent),  403. 
F-usulina  cylindrica,  409. 
Fusus  contrarius,  170;   F.  quadricostatu*, 

181. 

GALAPAGOS  ISLANDS,  animals  of,  325. 
Galeocerdo  latidens,  tooth  of,  215. 
Galerites  albogalerus,  245. 
Gallionella  distans,  G.ferruginea,  in  tripoli, 

25.  • 

Ganges,  buried  soils  in  delta  of,  384. 
Garnets  in  altered  rock,  480. 
Gases,  subterranean  rocks  altered  by,  595. 
Gault  of  upper  cretaceous,  250. 
Gavarnie,  flexures  of  strata  near,  59. 
Geoloey  defined,  1. 
Gergovia,  Hill  of,  558. 
Gervillia  anceps,  lower  greensand,  259. 
Giant's  Causeway,  columns  at,  483.  - 
....  basalt,  age  of,  ISO. 
Gibbes,  E.  W.,  cited,  233. 
Girgenti,  limestone  of,  156. 
Glacial  phenomena,  northern,  origin  of,  138. 
Glaciers,  Alpine,  146. 

on  Caernarvonshire  mountains,  137. 

Glasgow,  marine  strata  near,  154. 
Glenroy,  parallel  roads  of,  86. 
Glen  Tilt,  granite  of,  566. 
Glyphoza  ?  diibia,  coal-measures,  885. 
Gneiss,  altered  by  granite,  570. 

in  Bernese  Alps,  599. 

....  at  Cape  Wrath,  568. 
....  near  Christiania, 570. 
....  described,  588. 
Gold,  age  of,  in  Ireland,  629. 

,  age  of,  in  Ural  Mountains,  630. 

Goldfuss,  Prof.,  on  reptiles  in  coal-field,  397. 
Goniatites  crenistria,  G.  evolutus,  408;    <?« 

Listeri,  886. 

Gorgonia  infundibuUformis,  852. 
Goppert,  Prof.,  on  beds  of  coal,  360. 
....  on  petrifaction,  40. 
Gradual  increase  of  strata,  22. 
Graham's  Island,  488,  529. 
Grampians,  old  red  conglomerates  in,  47. 
Granite  described,  7,  560. 
. . . .,  passage  of,  into  trap,  565. 
,  porphyritic,  563. 


INDEX. 


677 


Granite  and  limestone,  junction  of  in  Glen  Tilt, 

566. 

.   . .,  syenitic,  talcose,  and  schorly,  564. 
.   ..  of  Cornwall  and  Dartmoor,  593. 
.   ..  of  Swiss  Alps,  613. 

..  rocks  in  connection  with  mineral-reins, 

630. 

...  of  Saxony,  583. 
.  ..,  oldest,  5S2. 
.  ..,  varieties  of,  568. 
.     .  veins  in  Cornwall,  569. 
.     .  veins  in  Cape  Wrath,  568. 
.     .  veins  in  Table  Mountain,  567. 
.     .  vein  in  White  Mountains,  574. 
.     .  of  Arran,  age  of,  583. 
.     .  near  Christiania,  531. 
.     .  dikes  in  Mount  Battock,  567. 
Graphic  granite,  562. 
Grahite    owder  of,  consolidated  by  pressure, 


Graptolites,  442. 

Grdptol&ius  Ludensix,  Silurian,  437. 

Grasshopper,  wing  of,  in  coal-measures,  386. 

Gratelonp,  M.,  on  fossils  in  chalk,  254. 

Granwacke,  term  explained,  429. 

Great  (or  Bath)  Oolite,  305. 

Greenland,  sinking  of  coast  of,  46. 

Greensand,  fossils  of,  251. 

....,  lower,  256. 

,  upper,  250. 

Greensburg,  Pennsylvania,  footprints  of  rep- 
tile in  coal-strata  at,  397. 

Greenstone,  467. 

,  dike  of,  in  Arran,  477. 

Gres  de  Beauchamp,  Paris  Basin,  226. 

Greystone.  volcanic  rock,  473. 

Griffiths,  Mr.,  on  geology  of  Ireland,  359. 

Grignon,  fossil  shells  near,  226. 

Grit  defined,  11. 

Gryttacris  lithantJiraca,  wing  of,  386. 

Gryphcea  coated  with  Serpulan.  22. 

arcuata,  G.  incur-to,  29,  318. 

—  columba,  G.  glolosa,  247;  G.  virgula, 
301. 

Gryphite  limestone,  or  lias,  318. 

Guadaloupe,  human  skeleton  of,  120. 

Gunn,  Mrs .  on  Norwich  flints,  244. 

Gutbier,  Col.  von,  on  Permian  flora.  356. 

Gyrolepis  tenuistriatus,  scale  of,  336. 

Gypseous  eocene  marls,  223,  224. 

Gypsum  defined,  13. 

HALL,  Sir  Jas.,  experiments  on  fused  minerals, 

528. 
.....  on  curved  strata,  48. 

...,  Capt  B.,  cited,  476.  523,  567. 
ffalysites  catenulatua,  Silurian,  435. 
Hamilton,  Sir  W.,  on  eruption  of  Vesuvius, 

526. 

Hamites  spiniger,  ganlt,  251. 
Harris,  Major,  on  salt  lake  in  Ethiopia,  344. 
Hartung.  Mr.  G.,  on  Teneriffe,  510. 
...., on  Madeira,  514,  518. 
Hartz.  bunter-sandstein  of.  335. 
Hastings,  Lady,  fossils  collected  by,  211. 
Hastings  sand,  262,  2-53. 
Hautes  Alpes.  rocks  of,  579. 
Haiiy  cited,  463. 

Hawkshaw,  Mr.,  on  fossil  trees  in  coal,  372. 
Hayes,  Mr.  T.  L.,  on  icebergs,  127. 
Headon  Hill  sands  described,  212. 
....  series  of  Isle  of  Wight  described,  210. 
Hebert,  M,  on  upper  eocene  beds,  184 

,  on  age  of  Kleyn  Spawen  beds,  184 

on  pisolitic  limestone,  236. 

Hebrides,  dikes  of  trap  in,  477. 

Heidelberg,  varieties  of  granite  near,  563. 

Heliolites  porosa,  422. 

Helix  labyrinthica,  211 ;  H.  occlusa,  209 ;  H. 

plebeia.Wl;  H.  Turonensis,  %Q. 
Uemicidaris  Purbec.kenxis,  294. 
Hemipnewtex  radlatux,  233. 
Ifemitelites  Brovmii,  314 
Uempstead  beds,  Isle  of  Wight,  185,  192. 


Henfrey,  Mr.  A.,  on  food  of  Mastodon,  144    . 
Henslow,  Prof.,  on  fossil  cetacea  in  Suffolk, 

173. 
. . . .,  on  fossil  forests,  297. 

,  on  altered  rock  near  Plas  Newydd,  480. 

HerscheL  Sir  J.,  on  slaty  cleavage,  602. 
Hertfordshire  pudding-stone,  35. 
Hesse  Cassel,  sands  of,  186. 
Heterocercal  fish,  tail  of,  353. 
Hibbert,  Dr.,  on  volcanic  rocks,  542,  552. 

,  on  coal-field  at  Burdiehouse,  386. 

High  Teesdale,    garnets    in  altered   rock  at, 

Hildburghausen,  footprints  of  reptile  at,  835, 
337. 

Himalaya,  tertiary  Inammalia  of,  182. 

,  elevated  fossiliferous  rocks  in,  4. 

Hippopodium  ponderosum,  lias,  319. 

Hippopotamus,  tooth  of,  166. 

Hippurites  organisans,  chalk,  253. 

Hippnrite  limestone,  253. 

Hitchcock,  Prof.,  on  footprints,  346. 

Hoffmann,  Mr,  on  Lipari  Islands,  cited,  595. 

. . . .,  on  cave  near  Palermo,  74 

,  on  Carrara  marble,  612. 

Hooghley  River,  analysis  of  water  of,  41. 

Holopty'chius  nobilissimm,  scale  of,  414 

....  Ribberti,  tooth  of,  396. 

Homalonotus  armatus,  425. 

delphinocephalus,  437. 

Homocercal  fish,  tail  of,  353. 

Hopkins,  Mr.,  on  fractures  in  Weald,  280. 

Horizontal  strata,  upheaval  of,  45. 

Horizontally  of  strata,  15. 

....  of  roads  of  Lochaber,  88. 

Hornblende,  463. 

rock,  or  amphibolite,  473,  590. 

Hornblende-schist,  588,  596. 

Homer,  Mr.,  on  ecology  of  Eifel,  538. 

on  Holoptychius,  396. 

Homes,  Dr.,  on  shells  of  Vienna  tertiary  basin, 
179. 

Hubbard,  Prof,  on  granite-vein  in  White  Moun- 
tains, 377. 

Hugi,  M.,  on  Swiss  Alps,  614 

Humboldt,  on  uniform  character  of  rocks,  616. 

Hungary,  trachyte  of,  467. 

,  volcanic  rocks  of,  544. 

Hunt,  Mr.,  experiments  on  clay-ironstone,  886. 

Hntton.  opinions  of,  60. 

Hnttonian  theory,  92. 

ffycsna  spelcea,  tooth  of,  167. 

Hybodus  reticulatus,  tooth  and  ray  of.  321. 

....  plicatilis,  teeth  of,  336. 

Hyrnenocaris  vermicauda,  448. 

Hypersthene  rock,  473. 

Hypogene,  term  defined.  9. 

....  rocks,  mineral  character  of,  615. 

or  metamorphic  limestone,  589. 

IBBETSOX,  Capt..  on  chalk,  Isle  of  Wight,  250. 
Ice,  rocks  drifted  by,  120. 
Icebergs,  stranding  of,  135, 143. 

,  magnitude  of,  128. 

Iceland,  icebergs  drifted  to,  143. 
Ichthyolites  of  old  red  sandstone,  419. 
Ichthyosaurus  communis.  skeleton  of.  823; 

paddle  of,  324 
Igneous  rocks,  6. 

of  Sicbengebirge  and  Westerwald,  540. 

....  ofValdiNoto,  438. 
Iguanodon,  notice  of  the,  260,  262. 
Iguanodon  Mantelli,  teeth  of,  261. 
India,  cretaceous  system  in,  255. 

freshwater  deposits  of,  182. 

oolitic  formation  in,  332. 

Indusial  limestone,  Auvergne,  200. 
Inferior  oolite,  314. 
Infusoria  in  tripoli,  24 
Inland  sea-cliffs  in  south  of  England,  71. 
Inoceramus  Lamarckii,  chalk,  247. 
In&ct,  wing  of  nenropterous,  328. 
Insects  in  coal,  3S5. 
....  in  lias,  327. 


678 


INDEX. 


Insects  In  oolite,  809. 
....  in  Purbeck  beds,  800. 
Invertebrate  animals,  period  of,  453. 
Ireland,  coal  strata  of,  359. 

,  Devonian  plants  of,  414. 

....,  drift  in,  137. 

Isastrcea  oblonga,  I.  Tisburientts,  301. 

Ischia,  volcanic  cones  in,  525. 

. . . .,  post-pliocene  strata  of,  118. 

Isle  of  Wight,  freshwater  beds  of,  210. 

Isomorphism,  theory  of,  464. 

JACKSON,  Dr.  C.  T.,  analysis  of  fossil  bones, 

144. 
James,  Capt.,  on  fossils  in  drift,  South  Ireland, 

137. 
Java,  stream  of  sulphureous  water,  223. 

,  volcanoes  of,  492. 

Jobert,  M.,  on  Hill  of  Gergovia,  553. 

Joints,  601. 

Jorullo,  lava-stream  of,  574. 

Junghuhn,  Dr.,  on  Javanese  volcanoes,  492. 

Jura,  alpine  blocks  on,  148. 

limestone,  303. 

. . . .,  structure  o-f,  55. 

KANGAROO,  fossil  and  recent,  jaws  figured,  162. 
Kaup,  Prof,  on  footprints  of  Cheirotherium. 

337. 

Kaye,  Mr.,  on  fossils  of  Southern  India,  255. 
Keeling  Island,  fragment  of  greenstone  in,  242. 
Keilhau,  Prof,  cited,  581,  593. 
.....  on  dike  of  greenstone,  478. 
.....  on  foliation,  607. 

,  on  gneiss  near  Christiania,  570. 

,  on  granite,  571. 

Kelloway  rock,  34. 

Kentish  chalk,  sandgalls  in,  82. 

....  rag,  lower  greensand,  257. 

Keuper,  the,  333. 

Kilauea,  volcanic  crater  of,  490. 

Killas  in  granite  of  Cornwall,  593. 

Kilkenny  yellow  sandstone,  fossil   plants   of, 

Kimmeridge  clay,  300. 

King,  Dr.,  on  footprints  of  reptile,  398. 

King,    Prof.,  on    Permian  group   and  fossils. 

350. 

Kirkdalo,  cave  at,  160. 
Kyson,  in  Suffolk,  strata  of,  218. 

LABTRINTHODON  J^QEKI,  tooth  of,  338,  339. 

pachygnathus,  outline  of,  340. 

Lacustrine  strata  of  Auvergne,  202. 
Lagoons  at  mouth  of  rivers,  33. 

of  Bermuda  Islands,  240. 

Lake  craters  of  Eifel,  540. 

crater  of  Laaeh,  543. 

Lakes,  deposits  in,  8. 

Lamarck  on  bivalve  mollusca,  29. 

Lamna  elegans,  tooth  of,  eocene,  215. 

Land,  rising  and  sinking,  45. 

Landenian,  or  lower  eocene  beds,  235. 

Lapldification  of  fossils,  43. 

La  Eoche,  estuary  of,  14. 

Laterite,  471,  473. 

Lava,  469. 

....  current,  Auvergne,  546. 

....  current,  Madeira,  view  of,  518. 

,  relation  to  trap,  486. 

....  stream  of  Jorullo,  574. 

....  streams,  effects  of,  6. 

....  of  Stromboli,  574. 

Lea,  Mr.,  footprints  of  reptile  discovered  by, 

400. 

Leaf-bed,  miocene,  of  Isle  of  Mull,  179. 
....  in  Madeira,  515. 
Lead-veins  in  Permian  rocks,  630. 
Leda  amygdaloides,  218 ;  L.  DesJiayesiana, 

188;  L.oblonga,m. 
Lehman  on  classification  of  rocks,  90. 
Leibnitz,  theory  of,  94.  « 

Leidy,  Dr.,  on  supposed  cotaceans  of  the  clialk, 


Lepidodendra,  862. 

Lepidodendron,  stem  of,  from  Ireland,  414. 

....  Sternbergii,  363. 

Lepidostrobus  ornatus.  363. 

Lepidotus  gigas,  scales  of,  320. 

....  Mantelli,  teeth  and  scale  of,  262. 

Leptcena  depressa,  445 ;  L.  Moorei,  319. 

Leptignite,  or  whitestone,  564. 

Lewes,  coomb  near,  276. 

Lias,  317. 

.  and  oolite,  origin  of,  328. 

.,  fossil  plants  of,  328. 
.  in  United  States,  330. 
.  period,  volcanic  rocks  of,  555. 
.  .,  plutonic  rocks  of,  579. 
Liebig,  Prof.,  on  conversion  of  coal  into  lignite, 

. . . .,  on  preservation  of  fossil  bones  in  caverns, 

161. 

Lima  gigantea,  318 ;  L.  Hoperi,  247. 
Lima,  South  America,  recent  strata  of,  120. 
Limagne  d' Auvergne,  freshwater  formations  of, 

197. 
Limburg,  or  upper  eocene  strata  of  Belgium, 

l'8b» 

Lime  in  solution,  source  of,  42 ;  scarcity  of,  in 

metamorphic  rocks,  617. 
Limestone  brecciated,  851. 
.,  crystalline,  851. 
.,  compact,  352. 
.,  fossiliferous,  352. 
.,  hippurite,  252. 
.,  indusial,  Auvergne,  200. 
of  Jura,  303. 
,  magnesian,  350. 
,  mountain,  fossils  of,  403. 
,  primary  or  metamorphic,  589. 
of  Devonian  system  in  Germany,  421. 
Limulus  rotundatus,  coal-measures,  385. 
Lindley,  Dr.,  cited,  265. 
Lingula  flags  of  lower  Silurian,  448. 
Lingula  Davisii,  448 ;  L.  Dumortieri,  173 ;  L. 

Lewisii,  433. 

Lipari  Islands,  rocks  altered  by  gases  in,  595. 
Lithodomi  in  beaches  of  North  America,  78. 

in  inland  cliifs,  73. 

Lithostrotion  basalt  if  or  me,  L.  flori/otvne,  Z. 

striatum,  404. 

Lituites  giganteus,  Silurian,  434, 
Llandeilo  flags,  439. 
Loam  defined,  13. 
Lochabar.  parallel  roads  of,  86. 
Lodes.    See  Mineral  veins,  620. 
Loess  of  valley  of  Ehine,  121. 

,  fossil  land-shells  of,  figured,  124. 

Logan,  Mr.,  on  coal-measures  of  South  Wales, 

360. 
. . . .,  on  footprints  in  Potsdam  sandstone,  452. 

,  on  fossil  forest  in  Nova  Scotia,  383. 

,  on  lower  Silurian  rocks  of  Canada,  446. 

London  clay,  216. 

Lonsdale,  Mr.,  cited,  158 ;  on  corals,  182. 

,  on  corals  of  Normandy,  177. 

,  on  fossils  in  white  chalk,  26. 

— ,  on  old  red  sandstone  of  South  Devon. 

419. 

,  on  Stonefield  slate,  309. 

Lonsdaleiafloriformis,  carboniferous,  404 

Louvain,  eocene  strata  near,  188. 

Loven  on  shells  of  Norway,  119. 

Lucina  serrata,  eocene,  216. 

Ludlow  formation,  430. 

Lund,  cited,  164. 

Lycett,  Mr.,  on  shells  of  oolite,  309. 

Lycopodium  densum  (recent),  363. 

Lyme  Reals,  lias  at,  327. 

Lym-Fiord  invaded  by  the  sea,  33. 

....,kelpin,  242. 

Lymnwa  caudata.  211 ;   L.  longiscata,  29, 

209. 
Lyons,  coal-mino  near,  374. 


MACACUS,  tooth  of,  Eocene,  219. 


INDEX. 


679 


M'Andrew,  Mr.,  on  scarcity  of  fish-bones  on 

sea-bottom,  455. 
MacCulloch,  Dr.,  on  age  of  Arran  granite,  584. 

.  .,  on  altered  rock  in  Fife,  481. 

.   .,  on  basaltic  columns  in  Skye,  433. 
.,  on  denudation.  6T. 
,  on  granite  of  Aberdeensbire,  565. 
,  on  hornblende-schist,  596. 
,  on  igneous  rocks  of  Scotland,  4S3. 
,  on  Isle  of  Skye,  36. 
,  on  overlying  rocks,  8. 
,  on  parallel  roads,  ST. 
,  on  trap-vein  in  Argyleshire,  477. 
Maclaren,  Mr.,  on  erratic  blocks  in  Pentlands, 

131. 

Maclure,  Dr.,  on  volcanoes  in  Catalonia,  531. 
Madurea  Logani,  Silurian,  446. 
Macropus  atlas,  162;  jaw  of,  162;  tooth  of, 

163. 

major  (recent),  jaw  of,  162. 

Madeira,  structure  of,  511-518. 

. ...,  trachyte  overlying  basalt  in,  522. 

,  view  of  dike  in  inland  valley  in,  476. 

Maestricht  beds,  237. 

Magnesian  limestone,  concretionary  structure 

of,  37. 

defined,  13. 

groups,  350. 

Maidstone,  fossils  in  white  chalk  of,  250. 
Mammalia,  extinct,  above  drift  in  United  States, 

143. 

,  extinct,  of  basin  of  Mississippi,  121. 

....,/08*il  teeth  o/ 166. 
Mam  mat,  Mr.,  cited,  69. 
Mammifer  in  Pnrbeck  beds,  295,  457. 
....  in  Stouesfield  oolite,  311. 

in  trias  near  Stuttgart,  341. 

Mammoth,  tooth  of,  165. 

Mansfield  in  Thuringia,  Permian  formation  at, 

356. 

Mantell,  Dr.,  cited,  242,  262,  264,  286. 
. . . .,  on  belemnite,  805. 

,  on  chalk-flints,  286. 

,  on  Brighton  elephant-bed,  287. 

. . . .,  on  freshwater  beds  of  Isle  of  Wight,  209. 

,  on  ignanodon,  260. 

,  on  wealden  group,  259,  286. 

,  on  reptile  in  old  red,  413,  589. 

ManteUia  megalophylla,  Purbeck,  296. 
Map  to  illustrate  denudation  of  Weald,  271. 

of  eocene  beds  of  Central  France,  195. 

Marble  defined,  12. 
Marl  defined,  18. 

in  Lake  Superior,  36. 

,  red  and  green  in  England,  335. 

Marl-slate  defined,  13. 
Marsupites  Milleri,  chalk,  245. 
Martin,  Mr.,  cited,  280. 

,  on  cross  fractures  in  chalk,  274 

Martins,  Mr.  C.,  on  glaciers  of  Spitzbergen,  142. 
Massachusetts,  plumbago  in,  596. 
Mattodon  angustidens,  tooth  of,  165. 
Mastodon  giganteus,  in  United  States,  143. 
Mastodonsaurus,  tooth  of,  338. 
Mayence  basin  tertiaries,  190. 
May  Hill,  Silurian  strata  of,  431. 
Mediterranean  and  Eed  Sea,  distinct  species  in, 

100. 

,  deposits  forming  in,  99. 

Meaalodon  cucullatus,  423. 
Megatherium,  tooth  of,  S.  America,  167. 
Melania  inouinata,  29, 220 ;  M.  turriti9»ima, 

208. 

Mtlanopsis  buccinoidea  (recent),  29. 
Melaphyre,  or  black  porphyry,  473. 
Menai  Straits,  marine  shells  in  drift,  136. 
Mendips,  denudation  in,  63. 
Mersey,  in  Kent,  ancient  channel  of,  120. 
Metalliferous  veins.    See  Mineral  veins. 
Metals,  supposed  relative  ages  of,  62S. 
Metamorphic  rocks,  537. 
. . . .,  defined,  8. 
,  less  calcareous  than  fossiliferons  rocks,  616. 

...,  order  of  succession  of,  615. 


Metamorphic  rockg,  glossary  of,  590. 

strata,  origin  of,  591. 

structure,  origin  of,  536. 

Meteorites  in  drift,  151. 

Mexico,  lamination  of  volcanic  rocks  in,  605. 

Meyer,  M,  H.  von,  cited,  153. 

,  on  reptile  in  coal,  497. 

,  on  sandstone  of  the  Vosees,  335. 

,  on  Wealden  of  Hanover  and  Westphalia, 

Mica-schist,  584. 

Micaceous  sandstone,  origin  of,  14. 
Micraster  cor-anguinum,  chalk,  245. 
Microconchus  carbonarius,  carboniferous,  384. 
Microlestes  antiquus,  teeth  of,  triassic  mam- 

mifer,  340. 

Miller,  Mr.  H.,  on  origin  of  rock-salt,  344. 
. . . .,  on  old  red  sandstone,  412,  418. 

,  on  fossil  trees  of  coal  near  Edinburgh,  376. 

Minchinhampton,  fossil  shells  at,  308. 
Mineral  character  of  aqueous  rocks,  10,  97. 
composition,  test  of  age  of  volcanic  rocks, 

521. 

springs,  connected  with  mineral-veins, 627 

veins  and  faults,  618,  620. 

veins  of  different  ages,  620. 

veins,  pebbles  in,  622. 

veins,  various  forms  of,  619. 

veins  near  granite,  624. 

Mineralization  of  organic  remains,  38. 
Minerals,  table  of  analyses  of  simple,  475. 
Miocene  faluns  of  the  Loire,  176. 

formation,  175. 

....  formation  in  Isle  of  Mull,  179. 

in  United  States,  180. 

. . . .,  (lower),  strata  of  Isle  of  Wight,  185. 
....  mammalia  of  Sewalik  Hills,  182. 

of  the  Bolderberg,  178. 

period,  volcanic  rocks  of,  538. 

,  term  defined,  116; 

Mississippi,  fluviatile  strata  and  delta  of,  3, 121, 

122. 

Mitchell,  Sir  T.,  on  Australian  caves,  162. 
Mitscherlich,  Prof.,  on  augite  and  hornblende, 

. . . .,  on  mineral  composition  of  Somma,  526. 

Mitra  scabra,  Barton  clay,  213. 

Modiola  acuminata,  Permian,  351. 

Modon,  lithodomi  in  cliff  at,  73. 

Molasse  of  Switzerland,  179. 

Monkey,  tooth  of,  eocene,  219. 

Mons,  flexures  of  coal  at,  53. 

Mont  Blanc,  talcose  granite  of,  577. 

Mont  Dor,  Auvergne,  545. 

Montlosier,  M.,  on  Auvergne  volcanoes,  550. 

Moraine,  term  explained,  ~123. 

Moraines  of  glaciers,  147. 

Morea,  inland  sea-cliffs  of,  73. 

....',  trap  of,  555. 

Morris,  Mr.,  on  fossils  at  Brentford,  153. 

Morton,  Dr.,  on  cretaceous  rocks,  254. 

Morven,  basaltic  columns  in,  483. 

Mosasaunis  Camperi,  jaws  of,  from  Maes 

tricht,  238. 

Mountain  limestone,  fossils  of,  403. 
Mull,  Isle  of,  Miocene  leaf-bed  of,  119. 
Miinster,  Count,  on  fossils  of  Solenhofen,  302. 
Murchison,  Sir  E.,  cited,  278,  285,  287. 
.   .  ,  on  eocene  gneiss,  599. 

,  on  volcanic  rocks  of  Italy,  530. 

,  on  new  red  sandstone,  336. 

,  on  age  of  Alps,  231. 

,  on  age  of  gold  in  Eussia,  629. 

,  on  erratic  blocks  of  Alps,  150. 

,  on  granite,  580,  583. 

,  on  primary  strata  in  Eussia,  129. 

,  on  joints  and  cleavage,  601. 

,  on  old  red  sandstone  of  S.  Devon,  419, 422. 

,  on  pentamerus,  433. 

,  on  Sflnrian  strata  of  Shropshire,  558. 

,  on  Swiss  Alps,  614 

,  on  term  Permian,  350. 

,  on  term  Silurian,  429. 

,  on  tileston«s,  430. 


680 


INDEX. 


Murchisonia  graciUs,  Silurian,  446. 
Murex  atoeolatus,  red  crag,  170. 
Muschelkalk,  338. 
Myliobatea  Edwardsi.  teeth  of,  Bracklesham, 

215. 
Mytilus  septifer,  Permian,  351. 

NAGELFLUH,  or  conglomerate  of  Alps,  179. 
Naples,  post-pliocene  formations  near,  524. 

,  recent  strata  near,  117. 

,  rising  of  land  at,  118. 

Nassa  granulata,  red  crag,  170. 
Natica  (recent),  spawn  of,  417. 

clausa,  130 ;  N.  helicoides,  155. 

Nautilus  cent  rails,  N.  ziczac,  218;  N.  Dani- 

cus,  239;  N..phcaiu8,  258;  N.  truncatus, 

319. 

Navarino,  lithodomi  found  in  cliff  at,  73. 
Nebraska,  U.  S.,  upper  eocene  of,  206. 
Necker,  M.  L.  A.,  cited,  569. 
. .   .,  on  composition  of  cone  of  Somma,  526. 
. .   ..on  granite  in  Arran,  584. 
. .   .,  on  granitic  rocks,  571. 
..  .,  on  Swiss  Alps,  614. 
. .   .,  terms  granite  "  underlying,"  8. 
Nelson,  Capt.,  drawing  of  Bermuda,  79. 

,  on  chalk  of  Bermuda  Island,  240. 

Neocomian,  or  lower  cretaceous,  256. 

Neozoic  type  of  corals,  403. 

Neptunian  theory,  91. 

NerincBd  Goodhallii,  N.  hieroglypMca,  303. 

Nerita  conoidea,  Ml  Schemidelliana,  228 ;  2T. 

costulata,  308 ;  N.  granulosa,  30. 
Neritina  concava,  211 ;  JW.  globvilus,  30. 
Newcastle  coal-field,  great  faults  in,  64. 
Newcastle,  fossil  tree  near,  311,  317. 
New  Jersey,  cretaceous  strata  of,  255. 

,  Mastodon  gigaateus  in,  143. 

New  red  sandstone,  distinction  from  old,  832. 

,  its  subdivisions,  333. 

of  United  States,  346. 

,  trap  of,  555. 

New  York,  Devonian  strata  of,  426. 

,  Silurian  strata  of,  444. 

New  Zealand,  absence  of  quadrupeds,  164. 
Niagara  limestone,  Silurian  fossils  of,  445. 

recent  shells  in  valley  of,  144. 

Nipadites  eliipticus,  216. 
Nodosaria,  chalk,  26. 
Noeggerath,  M.,  cited,  538. 
Noeggeratlda  cuneifolia,  357. 
Nomenclature,  changes  of,  93. 
Norfolk,  buried  forest,  133, 136, 153. 
. . . .,  drift,  132. 

Normandy,  chalk-cliffs  and  needles,  269. 
Northwich,  beds  of  salt  at,  343. 
Norwich  crag,  fluvio-marine,  154. 

,  sandpipes  near,  82. 

Nova  Scotia,  coal-seams  of  Cape  Breton,  312. 

,  fossil  forest  of  coal  in,  320. 

Nucula,  Cobboldice,   155 ;    Jf.  Deshayesiana, 

183. 
Nummulites,  whether  found  in  upper  eocene, 

189. 
Nummulites  earponens,  231 ;  .A7".  Icevigata,  215 ; 

2T.  Puschi,  230. 
Nummulitic  formation,  229. 
Nyst,  M.,  cited,  1S8. 

OBOLUS  APOLIJNIS,  Eussia,  444. 

Oenyhausen,  M.  von,  on  Cornish  granite  veins, 

569. 

Ohio,  Falls  of,  Devonian  coral-reef  of,  427. 
Old  red  sandstone,  411. 

,  in  Forfarshire,  598. 

,  trap  of,  558. 

OldKamia  antiqua,  0.  radiata.  449. 
Olenus  mierurus,  Cambrian,  448. 
OUva  Dnfreanli  t  miocene,  178. 
Olot,  extinct  volcanoes  near,  531. 
Omphyma  turinnatum,  Wenlock,  435. 
Onchus  fonnistfiatus,  Silurian,  432. 
Oolite,  291. 
and  lias,  origin  of,  319. 


Oolite,  inferior,  fossils  of,  314. 

in  France,  293. 

,  plutonic  rocks  of,  579. 

,  term  defined,  12. 

,  volcanic  rocks  of,  555. 

Oolitic  group  in  France,  293,  302. 
....,  United  States,  330. 
Opkioderma  Egertoni,  lias,  320. 
Ophite  and  ophiolite,  473. 
Opossum,  part  of  jaw  of,  219. 
Orbigny,  M.  d',  cited,  253. 

,  on  fossils  of  nummulitic  limestone,  233. 

,  on  subdivisions  of  cretaceous  series,  237. 

,  on  Vienna  basin  forarninifera,  179. 

Organic  remains,  criterion  of  age  of  formation, 

,  test  of  age  of  volcasic  rocks,  521. 

Ormerod,  Mr.,  on  trias  of  Cheshire,  343. 
Orthis  elegantula,  481 ;  0.  grandis,  0.  trice- 

naria,  0.  vespertilio,  440. 
Orthoceras  laterale,  408 ;  0.  Ludense,  0.  ven- 

tricosum,  434. 

Orthoclase,  or  common  felspar,  463. 
Osborne,  or  St.  Helen's  series,  Isle  of  Wight, 

192,  210. 

Osnabruck,  in  "Westphalia,  tertiary  strata  of,  178. 
Ostrea  acuminata,  314;  0.  carinata,  0.  co- 
lumba,  0.  vesicularis,  247 ;  0.  ditforta,  294 ; 
0.  expansa,  0.  deltoidea,  301 ;  0  gregaria, 
303;  O.  Marahii,  316. 
Otodus  obliquus,  tooth  of;  215. 
Overlying,  term  applied  to  volcanic  rocks,  8. 
Owen,  Dr.  Dale,  on  oldest  fossiliferous  rocks  of 
Wisconsin,  453. 

,  Prof.,  cited,  161, 173,  262, 310,  312, 313, 338. 
,  on  amphitherium,  310. 
,  on  birds  in  New  Zealand,  165. 
,  on  bone-caves  in  England,  160. 
,  on  footprints,  347. 
,  on  fossils  in  Australia,  162. 
,  on  fossil  monkey,  218. 
,  on  fossil  quadrupeds,  163. 
,  on  ichthyosaurus,  323. 
,  on  reptife  in  coil,  397. 
,  on  serpent  of  Bracklesham,  214. 
,  on  snake  of  Sheppey,  217. 
,  on  thecodont  saurians,  303. 
,  on  zeuglodon,  233. 
Oxford  clay,  304. 
Oyster  beds,  220. 

PACIFIC,  coral-reefs  of,  240. 
Palcechinus  gigas,  465. 
Palceoniscus,  Permian,  outline  of,  353. 
PalcKoniscus  comptu*,  scale  of,  P.  elegans, 

scale  of,  P.  glap/iyruQ,  scale  of,  354. 
Palaeontology,  term  explained,  1<!3. 
Palceophis  typhceuft,  vertebrae  of,  214. 
Palceosaurus  platyodon,  tooth  of,  355. 
Palceotherium,  magnum,  outline  of,  210 
Palagonia,  dikes  at,  529. 
Palagonite  tuff;  470. 
Palermo,  caves  near,  74. 
Palma,  Isle  of,  map  of,  495. 

,  structure  of,  494-508. 

Paludina  (Auvergne).  201 ;  P.  lenta,  29, 193. 
....  marginata,  P.  minuta,  132. 

(Mayence),  190 ;  P.  orbicularis,  209. 

Pampas,  extinct  quadrupeas  of,  163. 

Paradoxides  Eohemicus,  Cambrian,  450. 

Parasmilia  centrabis,  chalk,  403. 

Parallel  roads,  86. 

Pareto,  M.,  on  Carrara  marble,  612. 

Paris  basin,  93. 

Parka  decipiens  of  Forfarshire,  417. 

Parkinson,  Mr.,  on  eras:,  110. 

Parrot,  Dr.  F.,  on  salt-lakes  of  Asia,  344. 

Patella  rugosa,  great  oolite,  308. 

Pear-Encrinite,  Brad  ford -clay,  306. 

Pearlstone,  volcanic  rock,  474. 

Pebbles  in  chalk,  241. 

Pecopteris  lonchitica,  roal,  361. 

Pecten  Beave.ri,  246;  P.  ixlandicus,  130;  P. 

jacobcBus,  158. 


INDEX. 


681 


Pecten  papyraeeus,  336;  P.  quinquecostatu*, 

247. 

Pegmatite,  variety  of  granite,  562. 
J'untacrinus  Briareus,  lias,  320. 
I>entann«nu  Knightii,  433 ;  P.  Icevit,  483. 
Pentland  hills,  Mr.  Maclaren  on,  181. 
Peperino,  volcanic  tuff,  474 
Pepys,  Mr.,  cited,  41. 
Permian  flora,  distinct  from  that  of  coal,  353. 

formation  of  Thuringia,  356. 

group  described,  350. 

Perna  Jfulleti,  lower  greensand,  253. 

Petrifaction  of  fossil  wood,  39. 

. ...,  process  of,  43. 

Philipni,  Dr.,  on  fossil  shells  near  Naples,  118. 

.   . .,  on  Hesse  Cassel  beds,  186. 

.   . .,  on  marine  shells  in  caves  of  Sicily,  160. 

.   ...  on  tertiary  shells  of  Sicily,  156. 

Phillips,  Prof,  ci'ed,  308,  318. 

.  ..,  on  cleavage,  603. 

.   ...  on  terminology,  102. 

. . . .,  Mr.  W.,  on  kaolin  of  China,  11. 

Phacops  caudatus,  Silurian,  436. 

Phascolotherium  Bucklandi,  jaw  of,  312. 

Pha-sianetta  ffeddingtonenfii#,  coral-rag,  39. 

Pfdeboptei-is  contigua,  oolite,  314, 

Plwladomyafidieula,  oolite,  315. 

Phonolite,  or  clinkstone,  472. 

Phorus  extensus,  London  clay,  218. 

Phosphate  of  lime,  251. 

P/iragmoeeras  ventricosum,  Lndlow,  434. 

Phryganea,  indusice,  of,  201. 

,  (recent),  larva  of,  201. 

Phyllade  or  clay-slate,  590. 
Physa  BHstovii,  Purbeck,  295. 

columnaris,  P.  hypnorum  (recent),  29. 

Picton,  Nova  Scotia,  catamites  near,  318. 

Pilla,  M.,  on  age  of  Carrara  marble,  612. 

Piiiidiumamnicum,  133. 

Pisolitic  limestone  of  France,  235. 

Pitchstone,  or  retinite,  474. 

Placodus  gigas,  teeth  of,  335. 

Plagiostoma  giganteum,  318;  P.  Hbperi,  P. 

spinosum,  247. 
Planitz,  tripoli  of,  26. 

Planorbis  di&ciis,  209 ;  P.  euompfialus,  29, 211. 
P  as  Newydd,  rock  altered  by  dike  near,  480. 
Plastic  clays,  219. 
Playfair,  cited,  45,  92. 

,  on  faults,  62. 

. . . .,  on  Huttonian  theory  of  stratification,  60. 
Plectrodm  miruMlis,  432. 
Pleaiosaurus  dolicfiodiirus,  323. 
Pleurodictyum  problematic-urn,  425. 
Pleurotoma  attenuata,  216  ;  P.  rotata,  31. 
Pleurotomaria  carinata,  P.flammigera,  406. 
Pleurotomaria  granulata,  P.  ornata,  315. 
Plieninger,  Professor,  on  triassic  mammifer,  340. 
Pliocene,  newer,  period,  126. 

,  newer,  strata,  152. 

strata  in  Sicily,  155. 

,  older,  in  United  States,  180. 

...  strata,  167. 

period,  volcanic  rocks  of,  529,  530. 

,  term  defined,  116. 

Plomb  du  CantaL,  described,  552. 
Plumbago  in  Massachusetts,  596. 
Plutonic  rocks,  7,  573. 

of  carboniferous  period,  580. 

....  of  oolite  and  lias,  5T9. 

,  recent  and  pliocene,  574, 

....  of  Silurian  period,  5S1. 

,  age  of,  how  tested,  573. 

Plutonic  and  sedimentary  rocks,  diagram  of,  576. 

Pluvial  action,  effects  of,  279. 

Podocarya,  fruit  of,  oolite,  313. 

Poggendorf,  cited,  594. 

Poikilitic  formation,  350. 

. . . .,  term  explained,  332, 

Poly co&lia  prof 'unda,  Permian,  403 

Pomel,  M.,  on  mammalia  of  Auvergne,  203, 421. 

Ponza  Islands  in  Mediterranean,  486,  605. 

Porphyritic  granite,  563. 

Porphyry,  467,  4oS. 


Portland,  Isle  of,  fossil  forest  in,  29T. 

Portland  stone,  300. 

Portlock,  Col.,  on  Tyrone  Silurian  rocks,  443, 

Posidonia  minuta,  triassic,  334. 

Posidonomya?,  Richmond,  U.  8^  331. 

----  Beoheri,  carboniferous,  410. 

Post-pliocene  formations,  116. 

____  ,  period,  volcanic  rocks,  523. 

Potsdam  sandstone  at  Keeeeville,  451. 

----  sandstone,  tracks  on,  452. 

----  sandstone  in  Canada,  446. 

Pottsville,  coal-seams  near,  383. 

----  ,  footprints  of  reptile  near,  400. 

Pozzolana,  36. 

Pratt,  Mr.,  on  ammonites,  304. 

.....  on  extinct  quadrupeds  of  Isle  of  Wight, 

209. 

Precipitation  of  mineral  matter,  41. 
Predazzo,  altered  rocks  at,  581. 
Prestwich,  Mr.,  cited,  69. 
____  ,  on  "Weald  denudation,  281. 
____  ,  on  English  eocene  strata,  203,  212,  216,  219. 
.....  on  coal-measures  of  Colebrook  Dale,  62, 

3S5. 

Prevost,  M.  C.,  on  Paris  basin,  223,  224,  225. 
Productus  oalviis,  P.  ftorridus,  352. 
Productus   antiquatus,  P.  semiretieulatus, 

405. 

Progressive  development,  theory  of,  453. 
Protogine,  or  talcose  granite,  564. 
Psammodus  poroaut,  tooth  of,  409. 
Psaronites  in  Germany  and  France,  357. 
Pseudocrinites  bi/asciatits,  436. 
Pterichihys,  old  red,  419. 
Pterodactylm  crasfsirostris,  302. 
PterophyUum  comptum,  314 
Pterygotue  Anglicue,  415  ;  P.  problematicus, 

Ptychodus  decurrew,  tooth  of,  249. 

Puggaard,  Mr.,  on  Moen  drift,  2S5. 

Pumice,  469. 

Pupa  muncorum,  124  ;  P.  tridens,  30. 

Purbeck  beds,  891,  293. 

Purpwroidea  nodulata,  oolite,  308. 

Puy  de  Tartaret,  548. 

Puy  de  Pariou,  551. 

Puzzuoli,  elevation  and  depression  of  land  at, 

525. 

____  ,  post-pliocene  strata  at,  117. 
Pygopterus  mandibularis,  scale  of,  354. 
Pyrenees,  cretaceous  rocks  of,  589. 
____  ,  curvatures  of  strata  in,  58. 
----  ,  granite  of,  593. 
----  ,  nummulitic  formation  of,  230. 
Pyrocene,  or  augite,  465. 
Pyrula  reticulata,  coralline  crag,  172. 

Q0ADRTJMAXA,  fossil,  219. 

Quarrington  Hill,  basaltic  dike  near,  520. 

Quartz,  561. 

Quartzite,  or  quartz-rock,  589. 


iosuz,  253. 
....  Mortoni,  chalk,  248. 
Kadnorshire,  stratified  trap  of,  558. 
Rain-prints,  fossil  in  coal-shale,  384 
Eamsay,  Prof.  A.  C.,  on  denudation,  68. 
____   on  granite  in  Arran,  584 
----   on  section  near  Bristol,  102. 
....  on  Welsh  glaciers,  137. 
____  on  foliation  of  crystalline  schists,  609. 
----   on  Caradoc  sandstone,  438. 
Rastritesperegrinux,  442. 
Kecent  strata  defined,  11T. 
____  ,  near  Naples,  117. 

Eedfield,  Mr.,  on  glacial  fauna  in  America,  139. 
____  ,  on  fossil  fish,  349. 
Red  sandstone,  origin  of,  342. 
Eed  Sea  and  Mediterranean,  distinct  species  in, 

100. 

____  ,  saltnessof,  345. 

Eeptile  in  old  r«d  sandstone  of  Morayshire,  412. 
Reptiles,  carboniferous,  396,  897. 
....  of  lias,  322. 


082 


IKDEX. 


Reptiles,  fossil  eggs  of,  125. 

,  fossil,  of  Nova  Scotia  coal,  401. 

Reptilian  done,  great  oolite,  310. 

footprints  in  coal-strata,  399. 

Retepora  Jlustracea,  352. 

Eetinite,  or  pitchstone,  474. 

Ehine  valley,  loess  of,  121. 

Rhinoceros  leptorliinus,  tooth  of,  166. 

Ehynchonella  spinosa,  315 ;  ft.  Wilsoni,  433. 

Bigi,  near  Lucerne,  conglomerate  of,  179. 

Riniula  clathrata,  great  oolite,  308. 

Bipple-mark,  formation  of,  19. 

ftissoa  Chastelii,  eocene,  193. 

Eiver-channels,  ancient,  395. 

Eiver,  excavation  through  lava  by,  535. 

terraces,  85. 

Eock,  term  defined,  2. 

Eocks,  four  classes  of,  contemporaneous,  9. 

,  classification  of,  90. 

Eocks,  composed  of  fossil  zoophytes  and  shells, 

,  trappean,  92. 

Eoderburg,  extinct  volcano  of,  543. 

Eogers,  Prof.  H.  D.,  on  coal-field,  United  States, 

389. 

.....cited,  393,  413,  427. 
....,  on  reptilian  footprints  in  coal,  891. 
. . . .,  on  Devonian  rocks,  U.  S.,  427. 
,  Prof.  W.  B.,  on  oolitic  coal-field,  United 

States,  330,  389. 

,  on  Devonian  rocks,  U.  S.,  427. 

Borne,  formations  at,  175,  580. 
Eomer,  F.,  on  chalk  in  Texas,  255. 
ftosalina,  chalk,  26. 
Eose,  Prof.  G.,  cited,  469,  557. 

,  on  hornblende,  464. 

Boss-shire,  denudation  in,  67. 
Rostellaria  macroptera,  eocene,  218. 
Eothliegcndes,  lower,  or  Permian,  856. 
Bubble,  term  explained,  81. 
Eupelmonde,  Upper  Eocene  beds,  188. 
Eussia,  erratic  blocks  in,  129. 

.  fossil  meteoric  iron  in,  151. 

',  Permian  rocks  in,  355. 

SAAEBEUCK  coal-field,  reptiles  found  in,  397. 

St.  Abb's  Head,  curved  strata  near,  49. 

St.  Andrew's,  trap-rocks  in  cliffs  near,  556,  557. 

St.  Helena,  basalt  in,  483,  528. 

St.  Helens,  or  Osborne  series,  I.  of  Wight,  192, 

210. 
St.  Lawrence,  gulf  of,  inland  beaches  and  cliffs, 

St.  Mihiel,  France,  inland  cliffs  near,  77. 

St.  Paul,  Island  of,  508. 

St.  Peter's  Mount,  Maestricht,  fossils  in,  237. 

,  sandpipes  in,  83. 

Salisbury  Crag,  altered  strata  of,  481. 
Salt  rock,  origin  of,  343. 

,  precipitation  of,  343. 

....,atNorthwich,  343. 
....,  lakes  of  Asia,  344. 

Salter,  Mr.,  on  fossils  of  Caradoc  sandstone, 
438. 

,  on  Caradoo  beds,  438. 

. . . .,  on  Silurian  fish,  432. 

,  on  Silurian  rocks  of  Canada,  446. 

San  Lorenzo,  recent  strata  at,  120. 
Sandpipes  near  Maestricht,  83. 

near  Norwich,  82. 

,  or  sandgalls,  term  explained,  82. 

Sandstone,  with  cracks  in  Wealden,  263. 
Sandwich  Islands,  coral-reef  in,  241. 

,  volcanoes  of,  489,  508,  528,  546. 

Sangatte,  near  Calais,  drift  of,  288. 
Sao  Mrsuta,  metamorphoses  of,  450. 
Saucats,  near  Bordeaux,  faluns  of,  178. 
Saurians  of  lias,  323. 

,  thecodont,  355. 

Saurichthys  apicalis^  tooth  of,  336. 
Saussure,  M.,  on  moraines,  147. 
....,  on  vertical  conglomerates,  47. 
Savi,  M.,  on  Carrara  marble,  612. 
Samicaxa  rugosa,  pleistocene,  330. 


Saxony,  granite  in,  583. 
.  Scacchi,  M.,  on  post-pliocene  strata,  118. 
Scaphites  cequalis,  '245 ;  S,  ffiaas,  258. 
Scarborough,  oolitic  plants  of,  314. 
Schist,  hornblende  and  mica,  588,  589. 
. . . , ,  argillaceous,  589. 
....,  chlorite,  589. 
Schizodus   Schlotheimi,   350;    S.  trwicatus. 

hinge,  350. 

Schorl-rock  and  schorly  granite,  564. 
Scoresby  on  icebergs,  127. 
Scoriae,  469. 

Scotland,  carboniferous  traps  of,  556. 
....,  northern  drift  in,  130. 

,  old  red  sandstone  of,  414. 

Scrope,  Mr.,  cited,  305,  542,  546,  548,  550,  553, 

,  on  globular  structure  of  traps,  486. 

....,  on  Ponza  Islands,  605. 

,  on  trachyte,  basalt,  and  tuff,  470,  522. 

,  on  central  France,  197. 

Sea-cliffs,  inland,  71. 

Section  of  Wealden,  273. 

,  of  white  chalk  from  England  to  France, 

239. 

,  of  volcanic  rocks,  Auvergne,  547. 

Sedgwick,  Prof.,  on  brecciated  limestone,  351. 

,  on  Caradoc  beds,  438. 

,  on  concretionary  magnesian  limestone,  87. 

,  on  Coniston  grit,  439. 

. . . .,  on  Devonian  group,  419. 

,  on  garnets  in  altered  rock,  480. 

....,  on  granite,  580,  583. 

. . . .,  on  Permian  sandstones,  354. 

,  on  joints  and  cleavage,  600,  602,  609. 

,  on  mineral  composition  of  granite,  568. 

,  on  old  red  of  Devon  and  Cornwall,  419. 

,  on  structure  of  rocks,  600. 

,  on  trap-rocks  of  Cumberland,  559. 

Segregation  in  mineral-veins,  619. 

Semi-opal,  infusoria  in,  26. 

/Seraphs  convolutum.  Barton  clay,  213. 

Serpentine,  474. 

Serpula  attached  to  Gryphcea,  22;  toSpatan 

gus,  23. 

carbon  aria,  coal,  384. 

Serpulce,  and  Bryozoa,  on  Encrinite,  307. 
Serpula?,  on  volcanic  rocks,  in  Sicily,  157. 
Sewalik  Hills,  freshwater  deposits,  182. 
. . . . ,  miocene  strata  in,  182. 
Shale,  carbonaceous,  313. 

,  defined,  11. 

Shales  of  coal  near  Dudley,  593. 

Sharks,  teeth  of,  215. 

Sharpe,  Mr.  D.,  on  mollusca  in  Silurian  strata, 

446. 
, . . .,  on  slaty  cleavage,  609. 

,  «a  upper  greensand,  250. 

Shells,  fossil,  passim. 

,  fossil,  useful  in  classification,  114. 

. . . .,  recent,  28,  29,  30,  140,  144. 
Sheppey,  Isle  of,  fossil  flora  of,  216. 
Sherringham,  mass  of  chalk  in  drift,  134. 
Shetland,  granite  of,  440,  565, 568. 

,  hornblende-schist  of,  596. 

Shrewsbury,  coal-deposit  near,  384 

Sicily,  Fiume  Salso  in,  223. 

. . . .,  inland  cliffs  in,  74. 

. . . .,  newer  pliocene  strata  of,  155. 

. . . .,  terraces  of  denudation  in,  75. 

Sidlaw  Hills,  trap  of  old  red  sandstone,  553. 

Siebengebirge,  igneous  rocks  of,  540. 

Sienna,  formations  at,  174. 

Sigillaria,  866,  368. 

Sigillaria  larvigata,  coal,  367. 

Siliceous  limestone  defined,  12. 

rocks  defined,  11. 

Silliman,  Prof.,  cited,  574. 
Silurian,  name  explained,  429. 

. .  period,  plutonic  rocks  of,  581. 

. .  rocks,  table  of,  430. 

. .  strata  of  deep-sea  origin,  447, 

. .  strata  of  United  States,  444. 

. .  strata,  thickness  of,  442. 


INDEX. 


683 


Silurian  strata,  foot-tracks  in,  452. 

volcanic  rocks,  558. 

Simpson,  Mr.,  on  ice-islands,  135. 
Siphonia  pyriformis,  upper  greensand,  249. 
Siphonotreta  unguiculata,  Silurian,  444. 
Sivatherium,  extinct  ruminant,  182. 
Skapter  Jokul,  eruption  of,  521. 
Skye,  rocks  of,  481,  580. 

,  basaltic  columns  in,  4S3. 

....,  dikes  in  Isle  of,  478. 

,  sandstone  in,  36. 

Slates  of  Devon,  cleavage  of,  603. 

Slaty  cleavase,  602. 

8lickensides~  term  defined,  621. 

Smith,  Mr.,  of  Jordan  Hill,  on   pleistocene, 

140. 

Snags,  fossil,  375. 

Snakes'  «ggs,  fossil  at  Tonna,  near  Gotha,  125. 
Soissonnais  sanda,  228. 
Solenhofen,  lithographic  stone  of,  302. 
Solfatara,  decomposition  of  rocks  in  the,  595. 
Soinma,  525. 

lava  at,  478. 

Sopwith,  Mr.  T.,  models  by,  57. 

Sorby,  Mr.,  on  mechanical  theory  of  cleavage, 

603, 

Sortino,  cave  in  valley  of,  160. 
South  Devon  and  Cornwall,  old  red  of,  419. 
South  Downs,  view  of,  274. 
Sowerby,  Mr.  G.,  cited,  169. 
Spaccoforno,  inland  cliffs  at,  76. 
Spain,  volcanoes  in,  6,  531. 
Spalacotherium,  Purbeck  mammifer,  295,  457. 
Spatangw  (recent),  23 ;  8.  radiatus,  233. 

,  with  Serpula  attached,  23. 

Spezzia,  gulf  of,  calcareous  rocks  in,  612. 
Sphcerexochits  minis,  Wenlock,  436. 
Sphcerulites  agariciformis,  chalk,  253. 
Sphenopteris  crenata,  361 ;  S.  graoilis,  264. 
Spirifer  dis/unctus,  S.    Verneuilii,  421;  8. 
glaher,  8.  trigonalis,  406. 

mucrcnatus,  424:  S.  undulatus,  352:  & 

Walcottii,  318. 

Spirolina  stenostoma,  eocene,  227. 
Rpirorbis  carbonariu^  coal,  3S4. 
Spitzbergen,  glaciers  of,  142. 
Spondylus  spinosus,  chalk,  247. 
Sponges  in  chalk,  249. 
Spongilla  of  Lamarck,  in  tripoli,  25. 
. . . .,  spicnla  of,  tripoli,  25. 
Spring?,  mineraL    See  Mineral  springs,  626. 
Staffa,  basaltic  columns  in,  483. 
Stauria  astrceaformis,  Silurian,  403.  » 

Steno  on  classification  of  rocks,  91. 
Sternbergia,  structure  of,  368. 
Stigmaria  in  fossil  forest,  Nova  Scotia,  377. 
Stigmaria  and  Sigillaria,  367. 

ficoides,  coal,  368. 

Stirling  Castle,  rock  of,  altered  by  dike,  481. 

Stockholm,  post-pliocene  beds  near,  119. 

Stokes,  Mr.,  on  petrifaction,  43. 

Stonesfield,  fossil  mammalia,  310,  312. 

....  slate.  309. 

Storton  Hill,  footprints  at,  337. 

Strata,  term  defined,  2. 

arrangement  of,  determined  by  fossils,  21, 

. . .,  consolidation  of,  34 

. . .,  curved  and  vertical,  47,  58. 

. .  ,  elevation  of,  above  the  sea,  44. 

. .  ,  fossiliferons,  tabular  view  of,  104. 

. .  ,  horizontally  of,  15,  45. 

. .  ,  metamorphic  origin  of,  596. 

. .  ,  mineral  composition  o£  10. 

. .  ,  outcrop  of,  56. 

. .  ,  tertiary  classification  of,  109. 
Stratification,  forms  of,  13, 16,  47. 
. . . .,  unconformable,  59. 
Strickland,  Mr.,  on  new  red  sandstone,  336. 
Strike,  term  explained,  53. 
Stringocephalu*  Burtini.  Devonian,  423. 
Btromboli,  lava  of,  574. 

Strophomena,  depressa,  436 ;  S.  grandis,  440. 
Studer,  M.,  on  Swiss  Alps,  614. 


Studer,  M.,  on  boulders  of  Jura,  149. 

Stutchbury,  Mr.,  cited,  324,  355. 

Sub-Apenuine  strata,  110, 173. 

Subsidence  in  drift-period,  141. 

Succinea  amphibia,  29 ;  S.  elongata,  124. 

Suffolk  crag,  168. 

Sullivan,  Capt,  chart  of  Falkland  Islands,  88. 

Superga,  near  Turin,  tertiaries  of  Hill  of,  179. 

Superior,  Lake,  marl  in,  36. 

Superposition  of  aqueous  deposits,  96. 

Superposition  of  volcanic  rocks,  test  of  age, 

326. 

Snpracretaceons,  term  explained,  103. 
Sus  scrofa,  tooth  of,  166. 
Sussex  marble,  261. 
Swansea,  coal-measures  near,  859. 
. . . .,  stems  of  Sigillaria  at,  3T3. 
Sweden,  alum-schists  of,  451. 
Swiss  Jura,  structure  of,  55. 
Sydney  coal-field,  Cape  Breton,  3SO. 
Syenite,  564. 
Syenitic  granite,  564. 
Synclinal  line,  term  defined,  48. 

TABLE  MOTTNTAIN,  strata  horizontal  in,  45. 

,  granite- veins  in,  567. 

Table  of  fossiliferous  strata,  104. 

Tails  of  homocercal  and  heterocercal  fish,  353. 

Talcose  gneiss,  590. 

....  granite,  564. 

Tupirus  Americans  (recent),  tooth  of,  166. 

Tartaret,  Puy  de,  cone  of,  548. 

Teeth  of  mammals,  fossil  and  recent,  165, 166, 

167,  219,  233,  311,  341. 
Tderpeton  Elginense,  old  red,  412. 
Tellina  dbliqua,  pleistocene,  155. 
Temn4chinu8  exeavatus,  coralline  crag,  172 
Teneriffe,  Peak  of,  509,  511. 
Tentaculites  annulatus,- Silurian,  439. 
Terebelluin  convolutum,  T.fusiforme,  213. 
Terebratvla  (Atrypa)  affinis,  434. 
Mplicata,    T.  carnea,  T.  Defrancii,  T. 

octopttcata,  T.  plicatilit,  T.  pumilus,  246. 
diffona,S08;  T.fimbria.SW:  T.hastata, 

406;  T.lyra,ysi. 
navicula,  431 ;  T.  porrecta.  423 ;  T.  sella, 

259;  T.  Wil8oni,m 
Ttredina  personata,  fossil  wood  bored  by, 

Teredo  navalis  boring  wood,  24. 
Terra  del  Fnego,  145. 

Fucus  giganteus  in,  242. 

Tertiary,  term  explained,  109. 
....  deposits,  178, 189, 190. 

strata,  tabular  view  of.  104. 

Testudo  atlas,  of  Sew&lik  Hills,  182. 

Texas,  chalk  in,  255. 

Thames  valley,  freshwater  deposits  in,  152. 

Thamnastrcea,  coral-rag,  303. 

Thanet  sands  described,  221. 

Thecodont  saurians,  342,  355. 

Thecodontoaaurus,  tooth  of,  355. 

Thecosmilia  anniilaria,  303. 

Thelodm,  shagreen-scales  of,  4^2. 

Thirria,  M.,  on  oolitic  group  in  France,  329. 

Thuja  occidentalis,  in  stomach  of  mastodon, 

144. 

Thurmann,  M.,  cited,  55,  280,  308. 
Tilestones,  430. 

Tilgate  Forest,  remains  in,  262. 
Till,  term  explained,  133. 
....,  origin  of,  134. 
Tin,  veins  of,  in  Cornwall,  620,  627. 
Tiverton,  trap-porphyry  near,  555. 
Tongrian  system  of  M.  Dumont,  1S8. 
Touraine,  faluns  of,  175. 
Trachyte,  466. 

,  of  Hungary,  565. 

Trachytic  rocks,  older  than  basalt,  522. 

Transition,  term  explained,  91,  429. 

Trap,  term  explained,  460. 

....  dike  in  Fifeshire,  557. 

....,  globular  structure  of,  486. 

,  intrusion  of,  between  strata,  482. 


684 


INDEX. 


Trap,  various  ages  of,  556,  559. 

,  passage  of  granite  into,  564. 

in  Radnorshire,  558. 

....  rocks,  relation  to  lava,  486. 

rocks,  lithological  character  of,  522. 

Trappean  rocks,  91. 

Trap-tuff,  470. 

Trass  in  Lower  Eifel,  474,  543. 

Travertin,  how  deposited,  84. 

Tree-ferns  in  Permian  formation,  857. 

Tree-ferns  (recent).  362. 

Trias,  or  new  red  sandstone,  332,  333,  335. 

,  in  Cheshire  and  Lancashire,  836,  343. 

,  subdivisions  of,  333. 

Trigonellites  latus,  oolite,  302. 
Trigonia  caudata,  259;  T.  giblosa,  301. 
Trigonocarpum  olivceforme,  T.  ovatum,  369. 
Trigonotreta  undulata,  Permian,  852. 
Trilobites  in  Devonian  strata,  424 
. . . .,  metamorphoses  of,  444,  450. 

,  of  lower  Silurian,  441. 

Triloculina  inflata,  eocene,  227. 

Trimmer,  Mr.,  on  denudation  of  "Wealden,  285. 

,  on  sand-galls,  82. 

,  on  shells  in  drift  near  Menai  Straits,  136. 

Trinucleus  Caractaci,  T.  concentricus,  T.  or- 

natus,  441. 

Trionyx,  fragment  of  carapace  of,  208. 
Tripoli  composed  of  infusoria,  24. 
Trochus  Anglicus,  lias,  39. 
Trophon  clatkratum,  pleistocene,  130. 
Tuff,  volcanic,  and  trap,  6,  470. 
Tuffs  on  Wrekin  and  Caer  Caradoc,  558. 
Tuomey,  Mr.,  cited,  234. 
Tupaia  Tana  (recent),  jaw  of,  311. 
Turner,  Dr.,  cited,  41,  42. 
Turrilites  costatus,  chalk,  246. 
Turritella  multisulcala,  Bracklesham,  216. 
Tuscany,  volcanic  rocks  of,  530. 
Tynedale  fault,  64. 
Tynemouth  Cliff,  limestone  at,  351. 
Typhis  pungens,  Barton,  213. 

UDDEVALLA,  post-pliocene  strata  at,  119. 
....,  shells  of,  compared  with  those  near  Na- 
ples, 112. 

Underlying,  term  applied  to  granite,  8. 
Ungulite  grit  of  Russia,  443. 
Unio  littoralis  (recent),  28. 

,  Valdensis,  "Wealden,  263. 

United  States,  coal-field  of,  388. 

,  cretaceous  formation  in,  254. 

. . . .,  Devonian  rocks  of,  426. 

,  Devonian  strata  in,  426. 

,  eocene  strata  in,  231. 

,  older  pliocene  and  miocene  formations  in, 

,  oolite  and  lias  of,  330. 

Silurian  strata  of,  444 

Upper  greensand,  250. 

Upsala,  strata  containing  Baltic  shells  near,  129. 

Ural  Mountains,  gold  of,  629. 

Ursus  spelceus,  tooth  of,  167. 

VAL  DI  NOTO,  composition  of,  529. 
. . . .,  igneous  rocks  of.  487. 
. . . .,  inland  cliffs  in,  76. 
Valleys,  origin  of,  70. 

,  transverse  of  Weald,  275. 

Valorsine  granite,  569. 
Valvata,  pleistocene,  29. 
Veins,  mineral.    See  Mineral  veins,  618. 
Veinstones  in  parallel  layers,  623. 
Velay,  volcanoes  of,  552. 
Venericardia  planicosta,  eocene,  214 
Venetz,  M.,  on  Alpine  glaciers,  146. 
Ventrieulites  radiatux,  chalk,  248. 
Verneuil,  M,  de,  on  Devonian  of  the  U.  S., 

. . .,  on  horizontal  strata  in  Russia,  129. 
. ...,  on  lower  Silurian,  U.  S.,  445. 

,  on  Pentameru*  Knightii,  433. 

., ..,  on  Permian  flora,  354 


Vertebrata,  fossil,  progress  of  discovery  of,  458. 

,  not  found  in  lower  Silurian,  454 

Vesuvius,  eruption  of,  526. 

Vicenza,  basaltic  columns  near,  485. 

Vidal,  Capt,  survey  by,  495. 

Vienna  basin,  faluns  of,  179. 

Virginia,  U.  S.,  fossil  shells  in,  181. 

Virlet,  M.,  on  corrosion  of  rocks  by  gases,  595. 

,  on  geology  of  Morea,  £55. 

,  on  inland  cliffs,  73. 

Volcanic  dikes,  6,  426. 

mountains,  form  of,  5,  4S9. 

rocks,  age  of,  519. 

. . . .,  analysis  of  minerals  in,  475. 

,  Cambrian,  559. 

,  composition  and  nomenclature  of,  462. 

,  described,  5,  460. 

....  of  Hungary,  544. 

of  post-pliocene  period,  523. 

of  "Wales,  great  thickness  of,  444 

.....Silurian,  558. 

.....test  of  age  of,  519. 

....  tuff,  6,  470. 

Volcanoes  around  Olot  in  Catalonia,  583. 

. . . .,  extinct,  6,  530,  543,  545. 

....  in  Spain,  age  of,  536. 

,  newer,  of  Eifel,  540. 

....  of  Auvergne,  545. 
....  of  Canaries,  494. 
....  of  Java,  492. 

of  Sandwich  Isles,  489. 

Volteia  heterophylla,  335. 
Valuta  ambigua,  V,  atkleta,  213. 
......  Lamberti,  crag,  172. 

....  iatrella,  216 ;   F.  nodosa,  218. 

Von  Buch,  Baron,  cited,  470,  580,  581. 
....,  on  boulders  of  Jura,  M9. 

. . . .,  on  brown-coal,  191. 

....,  on  Canary  Islands,  494. 

,  on  Cystideae,  489. 

. . . . ,  on  land  rising,  45. 

WACK£,  or  argillaceous  trap,  474. 

Walchia  pintformis,  Permian,  356. 

"Wales,  ancient  glaciers  of,  136. 

Waller,  quoted,  93. 

Warren,  Dr.  J.  C.,  on  skeleton  of  Mastodon  gi- 

ganteus,  144. 

Waterhouse,  Mr.,  cited,  203,  812. 
Watt,  Mr.  G.,  experiments  on  fused  rocks,  528, 

594. 

Waves,  action  of,  on  limestone,  78. 
Weald  clay,  260. 

Weald  Valley,  denuded  at  what  period,  281. 
Wealden,  term  explained,  259. 
. . . .,  the  fracture  and  upheaval  of,  280. 

,  extent  of  formation,  264. 

,  plants  and  animals  of,  262,  265. 

Webster,  Mr.  T.,  cited,  109,  293,  297. 

Wellington  Valley,  caves  in,  162. 

Wener  Lake,  horizontal  Silurian  strata  of,  45. 

Wenlock  formation,  428. 

....,  shale,  437. 

Werner  on  classification  of  rocks,  91. 

....,  on  mineral  veins,  618. 

,  on  volcanic  rocks,  463. 

Westerwald,  igneous  rocks  of,  533,  540. 
Westphalia,  tertiaries  of,  178. 
Westwood,  Mr.,  on  beetles  in  lias,  328. 
Whin-Sil,  intrusion  of  trap  between  beds  at 

the,  482. 

Whinstone,  or  trap,  474 
White  chalk,  12,  239. 
White  Mountains,  granite-vein  in,  574. 
White  sand  of  Alum  Bay,  12. 
Whitestone,  or  Eurite,  564. 
Wigham,  Mr.,  on  fossils,  near  Norwich,  155. 
Wolverhampton,  fossil  forest  near,  374. 
Wood;  fossil  and  recent,  perforated  by  Mol- 

lusca,  24. 

....,  from  Colebrook  Dale,  structure  of,  369. 
,from  the  coal,  microscopic  structure  ef, 

40. 


Wood,  from  the  lias,  828. 

Wood,  Mr.   Searles,  on  Antwerp  crag  shells, 

173. 

. .  .,  on  fossils  of  crag,  169. 
. .    ,  on  fossils  of  Isle  of  Wight,  211. 

.,  on  number  of  shells  in  crag,  155. 
. .  .,  on  cetacea  of  crag,  173. 
..  .,  cited,  177. 
Woodward,  Mr.,  on  mammoth  bones,  Norfolk, 

153. 

Woolwich  beds  described,  220. 
Wrekin,  trap  of,  70. 


INDEX. 

Wyman,  Dr.,  cited,  23$. 
XIPHODON  gracile,  outline  of,  225. 
YORKSHIRE  Oolite,  plants  of,  313. 


685 


ZAMIA  spiralis  (recent),  297. 
Zechstein,  350. 

Zeuglodon  cetoides,  tooth  and  vertebra  of,  328. 
Zoophytes,  fossil,  22. 157. 182,  301, 303,  403,  404, 
422,435." 


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